Biology

cut vector and donor DNA then which Q. 4 Long answer type questions.
problem will arise in the formation of
rDNA or chimeric DNA? Explain. 1. Define and explain terms.

4. Match and write the pairs. i. Biopiracy ii. Biopatent

iii. Bioethus

Rcombinent protein It’s use in or for 2. Explain the steps in process of rDNA
technology with suitable diagrams.

i. platelet derived a. Anemia 3. Explain the gene therapy. Give two types
growth factor of it.

ii. a-antitrypsin b. cystic fobrosis 4. How are the transgenic mice used in
cancer research?

iii. Relaxin c. Haemophilia A 5. Give the steps in PCR or polymerase
chain reaction with suitable diagrams.

iv. Erythropoietin d. Diabetes 6. What is a vaccine? Give advantages of
oral vaccines or edible vaccines.

v. Factor VIII e. Emphysema 7. Enlist different types of restriction
enzymes commonly used in rDNA
vi. DNA ase f. Parturition technology? Write on their role.

g. Atherosclerosis 8. Enlist and write in breif about the
different biological tools required in
rDNA technology.

Project :

Visit the tissue culture laboratory in your area. Prepare powerpoint presentation on tissue
culture methodology and its applications.

292

13 Organisms and Populations

Can you recall? are adapted to their environments, not only
for their survival but also for propagation
1. What is an ecosystem? (multiplication).
2. What are the abiotic and biotic
Mean annual temperature (0C) 30 Desert Grassland
components of an ecosystem?
25
Natural world around us shows amazing
diversity of forms and complexity of relations. 22 Tropical forest
To understand these, we have to study
levels of organization in the living world 15
viz. macromolecules, cells, tissues, organs,
individual organism, population, communities, Temperate forest
ecosystems and biomes.
10
You have already studied in school, that
ecology is a study of the interactions among 5
organisms and between the organisms and their
physical (abiotic) environment. Term ecology 0 Coniferous forest
was first used by Reiter but E. Haeckel gave
substance to the term (introduced) ecology. -5

Ecological grouping of organisms is -10 Arctic and alpine tundra
nothing but ecological hierarchy. There are four
sequential levels with increasing complexity -15
of ecological (biological) organizations viz, 50 100 150 200 250 300 350 400 450
Organism, Populations, Communities and
Biomes. Individual organism is the basic Mean annual precipitation/ rainfall (cm)
unit of ecological hierarchy. Organisms of
same kind inhabiting a geographical area Fig. 13.1 : Distribution of major Biomes
constitute population. Several populations of with respect to annual temperature and
different species in a particular area constitute
community that interact with one another precipitation
in several ways. Biome constitutes a large
regional terrestrial unit delimited by a specific You have studied in earlier classes about
climatic zone having major vegetation zone the rotation of earth around the Sun and the tilt
(plant communities) and the associated fauna. of its axis, cause seasons. These seasons with
There are six major groups of terrestrial biomes. annual variation in precipitation in the form of
We shall explore first two levels viz, organism rain and snow, gives rise to formation of major
and populations. biomes of the earth like desert, rain forest,
grassland, tundra, etc.
13.1 Organisms and the environment
around: Regional and local variations within each
biome lead to the formation of a variety of
Ecology at the level of organism is basically habitats. Major biomes of earth are shown
the study of animal or plant physiology which in Fig. 13.1. On the Earth, life exists even in
helps us to understand how the organisms extreme and harsh habitats like scorching
deserts of Rajasthan, perpetually rain-soaked
forests of North Eastern states and high
mountain tops of Himalayas.

Find out

What are the key differences that
make such a great variation in the physical
and chemical conditions of different habitats?

Here, we must remember that it is not only
the physico-chemical (abiotic) components
that make up the habitat of an organism, but
the habitat also includes biotic components like

293

plants, pathogens, parasites, and predators of Table 13.2 : The differences between
the organism. We assume that over a period Habitat and Niche can be summarized as :
of time, the organism had through natural
selection, evolved adaptations to optimize its Habitat Niche
survival and reproduction in its habitat.
A habitat is an area, A niche is a concept,
Do you know ?
where a species lives of how an organism
Ethology - The term was coined by Hilaire
(1854) but was popularised by W. M. Wheeler and interact with lives or survives in
(1902). The term denotes (speaks for) the
study of behaviour of animals in relation to the other factors and the environmental
their environment.
prosper. conditions.
Ecology - The term was introduced by E.
Haeckel (1865) for the relationship of animals Habitat consists of Niches do not contain
and plants with their surroundings. numerous niches. such components.

Effect of temperature, Flow of energy from

rainfall and other one organism to other

abiotic factors. through ecosystem.

Habitat supports Niche supports a

numerous species at single species at a

a time. time.

Bionomics - Lankester (1890) coined this term Habitat is a physical Niche is an activity
for the study of relation between organisms to place. performed by
their environment. organisms.

Environmental biology (modern ecology) Habitat is not species Niche is species
- The term was introduced in 20th century
(G. L. Clarke 1964, Odum 1969) giving specific. specific.
emphasis on the functional or physiological
interrelationships between the organism and Definition of Habitat :
their surroundings. Place or area where a particular species

Biosphere - All the ecosystems on earth lives, is its habitat. Factors like the sunlight,
constitute biosphere. average rainfall, annual temperatures, type
of soil present and other abiotic (topographic)
Habitat and Niche : factors, affect the presence of organisms. These
Habitat is a place or the set of environmental factors help in determining the presence of the
particular type of species in the environment.
conditions around the organism to which it must
adapt to survive and prosper. The term Niche is Pond, river, ocean, etc. are the examples
used to denote the functional role played by an of habitat as many organisms are found in
organism in its environment (J. Grinnell 1917). the same place or habitat. These habitats can
Niche includes various aspects of the life of an be arboreal, terrestrial, aerial, aquatic, etc.
organism like diet, shelter, etc. The immediate surrounding of an organism,
sometimes also referred to as microhabitat,
A habitat defines the physical space of is an important concept to remember when
an organism with the other living or non- working with sedentary or weakly motile
living factors, while niche describes how organisms.
that organism is linked with its physical and
biological environment. In colloquial language Definition of Niche :
habitat is a postal address while niche is the The term niche was first time used by ‘J.
profession of organism.
Grinnell’. The term ecological niche is still
not well understood and is sometimes even
misused.

294

Niche is described as a position of a species We have seen earlier in the chapter that
in the environment like, what they do for their each habitat type is regulated by a number of
survival? how they fulfill their needs of shelter, abiotic or physico- chemical factors.
food? etc. Niche deals with the flow of energy
from one organism to another and hence, it is Key abiotic factors that influence any
important to understand, what an organism habitat are ambient temperature, availability
eats, how it interacts with other organisms, of water, light and type of soil.
etc. As soon as the niche is left vacant, other
organisms fill that position. The niche is 13.2 Major Abiotic Factors :
specific to each species, which means no two Temperature:
species can share the same niche.
It is the most ecologically relevant
If the species creates its own unique environmental factor. Average temperature
niche in an ecosystem, it would be helpful in on land varies from subzero levels in polar
reducing competition for resources among areas and high altitudes, upwards upto 50oC in
species. By taking an example of a bird, it tropical deserts in summer. Temperature also
can be understood that how these birds differ varies seasonally. It decreases progressively
in their eating habits, where some birds eat from the equator towards the poles and from
only insects, some only fruits and some can eat plains to the mountain tops. There are some
both and anything they come across. So here unique habitats such as hot springs (80 to
we can conclude that these birds living in the 1000C) and deep-sea hydrothermal vents where
same habitat differ in their niches because of average temperatures usually 400o C. Ambient
different eating habits. temperature affects the enzyme kinetics of the
cell and thus, the entire metabolism, activity
Three types of niches are found: and other physiology of the organism.

a. Spatial or habitat niche : It deals with the Only few organisms can tolerate and thrive
physical space occupied by the organisms. in a wide range of temperatures (eurythermal),
but, a vast majority of them are restricted to a
b. Trophic niche : It is on the basis of trophic narrow range of temperatures (stenothermal).
level of an organism in a food chain.
Find out
c. Multidimensional or hypervolume niche:
It considers number of environmental factors 1. Give names of eurythermal and
(both biotic and abiotic), the resulting space stenothermal animals and plants?
will be a hypervolume; not something that can
be perceived by the human mind. This space is 2. What will be the effect of increasing
called the hypervolume niche. Alternatively, global temperatures on the different
it is the position of an organism in the habitats and the organisms found in those
environmental gradient. habitats?

For every species, there is a fundamental Water: Availability of water is an important
niche and a realized niche. Fundamental niche factor affecting the organisms. As we know,
is the niche in the absence of all competitors, life on earth originated in water, its availability
this is highly improbable in nature. Hence, is so limited in deserts that only special
realized niche is more realistic approach, in adaptations are required to survive there. The
the presence of competition for the resources productivity and distribution of plants are also
available in the habitat. heavily dependent on water.

295

Organisms living in water bodies such as Soil: The nature and properties of soil are
oceans, lakes and rivers, have their own water- dependent on the climate, the weathering
related problems. For aquatic organisms the process.
chemical composition and pH of water are
important. Various characteristics of the soil such
as soil composition, grain size, determine
The dissolved salt concentration (measured the percolation and water holding capacity
as salinity in parts per thousand), is less than of the soil. These characteristics along with
5ppt in fresh waters of streams , lakes and pH, mineral composition and topography,
rivers, and 30-35ppt in the seas and oceans. determine the vegetation of an area. Vegetation
It may go up to 100ppt in some hypersaline in turn dictates the type of animals.
lagoons.
The abiotic factors that determine the type
Some organisms are tolerant for a wide of habitat, also show considerable diurnal and
range of salinities (euryhaline) but others are seasonal variations. The plants and animals
restricted to a narrow range (stenohaline). must adapt to these changes in order to survive
Many fresh water animals cannot live for long and flourish in the habitat. During the course
in sea water and vice versa because of the of their evolution, many species have evolved
osmotic problems, they would face. a relatively constant ‘internal’ environment
that permits all biochemical reactions and
Find out physiological functions to proceed with
optimum rate, and allow the species to flourish.
Give examples of an animal and plant The organisms try to maintain the constancy of
that can survive in fresh water as well as sea its internal environment (homeostasis) despite
water? variations in the external environmental
conditions. To survive and flourish in any
Light: Plants use light for photosynthesis, environment, organisms must adapt to the
which is only source of energy for the entire changes in the environment for which there are
ecosystem. Photosynthesis can occur only in following possibilities :
presence of sunlight. Many species of small
plants (herbs and shrubs) growing on forest i. Regulate: Some organisms are able to
floor are adapted to perform photosynthesis maintain homeostasis by physiological
optimally under very low light conditions and behavioural changes which ensure
because they are constantly overshadowed by constant body temperature, constant
tall trees. osmotic concentration, etc. All birds and
mammals are capable of such regulation
For animals too, diurnal and seasonal (thermoregulation and osmoregulation).
variations in light intensity and duration
(photoperiod) are clues for timing their foraging, ii. Conform: Most of animals and plants
reproductive and migratory activities. The cannot maintain a constant internal
availability of light on land is closely linked environment. Their body temperature
with that of temperature, since the sun is the changes with the ambient temperature. In
source for both. aquatic animals, the osmotic concentration
of the body fluids changes with that of the
Find out ambient water osmotic concentration. These
animals and plants are simply conformers.
What is the source of energy for the
life in deep ocean trenches where sunlight
does not reach?

296

Some species have evolved the ability organism (morphological, physiological, and
to regulate, within a limited range of behavioural) that enables the organism to
environmental conditions, beyond which survive and reproduce in its habitat.
they simply conform. If the stressful
environment is localized or only for a short Many desert plants have a thick cuticle
period of time, the organism may migrate on their leaf surfaces and have their stomata
or suspend its activities. in deep pits to minimize loss of water through
transpiration. They also have a special
iii. Migrate: The organism can move away photosynthetic pathway (CAM - Crassulacean
temporarily from the stressful habitat to acid metabolism) that enables their stomata
a more hospitable area and return when to remain closed during daytime. Some desert
stressful period is over. Many animals, plants like Opuntia, have their leaves reduced
particularly birds, during winter undertake (modified) to spines and the photosynthetic
long-distance migrations to more hospitable function is taken over by the flattened stems.
areas.
Mammals from colder climates generally
iv. Suspend: In plants, seeds serve as means to have shorter snout, ears, tail and limbs to
tide over periods of stress; they germinate to minimize the loss of body heat (Allen’s Rule.)
form new plants under favourable moisture In the polar seas, aquatic mammals like seals
and temperature conditions. They do so by have a thick layer of fat (blubber) below their
reducing their metabolic activity and going skin acting as an insulator to reduce loss of
into a state of ‘dormancy’. In animals, the body heat.
organism, if unable to migrate may go into
hibernation during winter e.g. polar bear. Can you tell?
Some snails and fish go into aestivation to
avoid summer heat. 1. What is homeostasis?
2. Why do animals need to maintain
Internet my friend
homeostasis?
Find out the difference between 3. What are the adaptations in animals
hibernation and aestivation.
living under crushing pressure at great
Do you know? depths of ocean?

1. Adaptation of plants for aquatic and Some organisms show behavioural
desert habitats. responses to cope with variations in their
environment. Desert lizards manage to keep
2. Adaptations of animals for aquatic and their body temperature fairly constant by
desert habitats. behavioural adaptations. They bask in the sun
and absorb heat, when their body temperature
13.3 Adaptation : drops below the comfort zone, but move into
To cope up with extreme variations in shade, when the ambient temperature starts
increasing. Some species burrow into the sand
their environment, some organisms respond to hide and escape from the heat.
through physiological adjustments, while
others do so behaviourally (like migration). 13.4 Population :
These are their adaptations. Therefore, we In nature, we rarely find isolated, single
can say that adaptation is an attribute of the
individuals. They live in groups in a well-
defined geographical area, share or compete

297

for similar resources, potentially interbreed It must be remembered, that absolute
and thus form a population. natality will be always more than realized
natality.
Although, it is an individual organism that
has to cope with changes in the environment, it Mortality is the death rate of a population.
is at the population level that natural selection Mortality rate or death rate, is a measure of
operates to evolve the desired traits. Population the number of deaths (in general, or due to
ecology is, therefore, an important area of a specific cause) in a particular population,
ecology because it links ecology to population in proportion to the size of that population,
dynamics, genetics and evolution. per unit of time. Mortality rate is typically
expressed in deaths per 1,000 individuals per
A population has certain attributes of year. Thus, a mortality rate of 9.5 (out of 1,000)
its own, which are different from those of an in a population of 1,000 would mean 9.5 deaths
individual. Basic physical characteristics per year in that entire population, or 0.95% out
of population are - its size and density. Size of the total.
speaks for the number of individuals in a
population while density tells us number of • Absolute Mortality : the number of deaths
individuals present per unit space, in a given under ideal conditions (with no competition,
time. Besides size and density, the other abundance of resources such as food and
characteristics include natality, mortality, water, etc.).
immigration, emigration, age pyramids,
expanding population, population growth • Realized Mortality : the number of deaths
forms and biotic potential. An individual has when environmental pressures come into
birth and death, but a population has birth rate play.
and death rate. It must be remembered that absolute

Natality is the birth rate of a population. mortality will be always less than realized
It has the greatest influence on a population’s mortality.
growth. Natality is a crude birth rate or specific
birth rate. Crude birth rate is used when Sex ratio: The sex ratio of the population
calculating population size (number of births affects and is reciprocally affected by birth,
per 1000 population/year), whereas specific death, immigration, and emigration rates.
birth rate is used relative to a specific criterion It is measured as the ratio of the number
such as age. E.g. If in a pond, there were 200 of individuals of one sex to that of the other
carp fish last year and through reproduction sex. The males and females in a ratio of 1:1
800 new fish are added, taking the current is generally the most common evolutionary
population to 1000, we calculate the birth rate stable strategy (ESS).
as 800/200 = 4 offspring per carp per year.
Can you tell?
• Absolute Natality : the number of births
under ideal conditions (with no competition, What can be the causes of deviation
abundance of resources such as food and from 1: 1 sex ratio in natural habitat?
water, etc.).
Internet my friend
• Realized Natality : the number of births
when environmental pressures come into 1. Find out the sex ratio of Indian population
play. and the state of Maharashtra.

2. What are the reasons behind deviation of
sex ratio among Indian population?

298

Age distribution and Age pyramid: In an area, if there are millions of termites
A population is composed of individuals / ants but only a few animals which feed on
them, stating that the population density of
of different ages. If the age distribution (per these predators is low, will be misleading.
cent individuals of a given age or age group) is
plotted for the population, the resulting structure In such cases, the biomass is a more
is called an age pyramid. For the purpose of meaningful measure of the population
simplicity, the entire population is divided into size. Total number is again not an easily
three age groups as Pre-Reproductive (age adoptable measure, if the population is huge
0-14 years), Reproductive (age 15-44 years) and counting is impossible or very time-
and Post- reproductive (45-85+ years). consuming. Sometimes, for certain ecological
investigations, there is no need to know the
Use your brain power absolute population densities; relative densities
serve the purpose equally well. For instance,
From the age pyramids given below the number of birds / insects caught per trap is
(Fig.13.3)- what will be your forecast for good enough measure of their total population
15 years from now for the populations of 1. density. We are mostly obliged to estimate
Kenya, 2. Australia, 3. Italy and 4. Hungary. population sizes indirectly, without actually
counting them or seeing them. The tiger census
The size of the population it can support in our national parks and tiger reserves is often
tells us a lot about its status in the habitat. The based on pug marks and fecal pellets.
population size, in natural habitat, could be
as low as less than 10 (Siberian cranes in bird Population Growth :
sanctuary) or go into millions (Chlamydomonas The size of a population for any species is
in a pond).
a dynamic parameter. It keeps changing with
Population size, more technically called time, depending on various factors including
population density (designated as N), need food, predation pressure and adverse weather.
not necessarily be measured in numbers only. In fact, these changes in population density
Although total number is generally the most that give us some idea whether it is flourishing
appropriate measure of population density, it is or declining.
in some cases either meaningless or difficult to
determine.

Male Female Male Female Male Female Male Female

Rapid Growth Slow Growth Zero Growth Negative Growth
e.g. Kenya, Nigeria e.g. Germany, Hungary
e.g. United States, Australia e.g. Denmark, Italy

Ages 0 -14 years Ages 15-44 years Ages 45 - 85+ years

Fig. 13.3 : Age pyramids for countries with rapid, slow, zero and negative population
growth rates.

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Density of population in a habitat during a Every species is capable of growing
given period, fluctuates due to changes in four exponentially under unlimited resource
basic processes. New births (B) and Immigration conditions, and reach enormous population
contribute to an increase in population density. densities in a short time. Darwin showed how
Deaths (D) and Emigration lead to decrease even a slow growing animal like elephant
in population density. Immigration (I) is the could reach enormous numbers. (provided food
number of individuals of the same species that and space remain unlimited).
have come into the habitat from elsewhere
during the time period under consideration. But resources like food and space are not
Emigration (E) is the number of individuals of always unlimited. They may be in the beginning;
the population who left the habitat during the but as the population density increases, so does
time period. the competition for those resources, resulting
in slowdown in the rate at which the original
So, if N is the population density at time ‘t’, population was growing. This results in logistic
then its density at time ‘t +1’ can be calculated or sigmoid growth curve.
as,
ii. Logistic growth: competition between
Nt+1 = Nt + [(B + I) – (D + E)] individuals for limited resources will weed out
the ‘weaker’ ones. Only the ‘fittest’ individuals
Growth Models: Does the growth of a will survive and reproduce. In nature, a given
population with time show any specific and habitat has enough resources to support a
predictable pattern? We have been concerned maximum possible number, beyond which
about unbridled human population growth and no further growth is possible. Let us call this
problems created by it in our country and it is limit as nature’s carrying capacity (K) for that
therefore natural for us to be curious if other species in that habitat.
animal populations in nature behave the same
way or show some restraint on growth. Diminishing
growth phase
i. Exponential growth:
Resources like food, space are essential

for any growth of a population. Ideally,
when resources in the habitat are unlimited,
each species has the ability to fully realize
its innate potential to grow in numbers. Then
the population grows in an exponential or
geometric proportion.
Population size Stationary phase
Growth (size or weight of the organism)
Log or
exponential phase

Lag phase

Time

Time Fig. 13.5 : Logistic growth curve of population
Fig. 13.4 : Exponential growth curve of
A population growing in a habitat with
population limited resources show initially a lag phase,
followed by phases of acceleration and
deceleration and finally an asymptote, when
the population density reaches the carrying
capacity. A plot of population density (N) in

300

relation to time (t) results in a sigmoid curve. It is obvious that in nature, animals,
This type of population growth is called plants and microbes do not and cannot live in
Verhulst-Pearl Logistic Growth. isolation but interact in myriad ways to form
a biological community. Interactions may be
Since resources for growth for most animal intraspecific i.e. existing between organisms
populations, are finite and become limiting of same population, and interspecific -between
sooner or later, the logistic growth model is members of different species. The interspecific
considered a more realistic one. interactions occur between minimum two
organisms- plants/ animals/ plant and animal.
Internet my friend Such interaction may be classified as four types
viz, neutralism, negative (harmful), positive
Gather from Census-data the population (benificial), and both positive and negative
figures for India for the last 100 years, plot interactions. Even in simplest communities,
them and check which growth pattern is many interactions exist, not all may be easily
evident? seen. Interspecific interactions arise from the
interaction of populations of two different
1. Think about it species. These interactions could be beneficial,
1. What will happen when carrying capacity detrimental or neutral (neither harm nor benefit)
to one of the species or both.
of any habitat is exceeded?
2. What could be the reasons behind Table 13.6 : Interspecific Interactions

enormous increase in human population? Sr. Type of interactions with Species
no. subdivisions
Under a particular set of selection AB
pressures, organisms evolve towards the most I Neutralism - no significant OO
efficient reproductive strategy. Some produce effect
a large number of small-sized offspring --
(Oysters, pelagic fishes) while others produce II Negative interactions
a small number of large-sized offspring (birds, a. Competition - direct --
mammals). interference type
b. Competition - resource - -O
Think about it use type
c. Amensalism ++
What can be the reason behind the +O
different reproductive strategies adopted by III Positive interactions ++
monocot plants like cereals/ pulses and dicot a. Symbiosis (Mutualism)
plants like mango? b. Commensalism +-
c. Protocooperation +-
13.5 Population Interactions :
There is no natural habitat, which has IV Both positive and negative
interactions
only one species or animals or plants. For any a. Parasitism
species, the minimal requirement is another b. Predation
species as food. Even a plant species, which
has photosynthetic abilities, cannot survive + = benifited
alone; it needs soil microbes to break down the - = inhibited
organic matter in soil and release the inorganic O = not affected
nutrients.

301

The various types of interactions are But the mutually beneficial system should
classified as per the nature of these interactions also be safeguarded against ‘cheaters’, for
to one or both the species. Both the species are example, animals that try to steal nectar
benefited in mutualism and both are harmed in without aiding in pollination. Plant-animal
competition. interactions often involve co-evolution of the
mutualists, that is, the evolutions of the flower
In parasitism and predation only one and its pollinator species are tightly linked with
species benefits (parasite and predator, one another.
respectively) and the interaction is detrimental
to the other species (host and prey, respectively). Competition:
The interaction where one species is benefitted Competition is the type of interaction
and the other is neither benefitted nor harmed is
called commensalism. In amensalism, on the where both the species are at a loss. Totally
other hand one species is harmed whereas the unrelated species may compete for the same
other is unaffected. resource e.g. in shallow creeks on the west
coast of Mumbai, visiting flamingos and
Mutualism: resident fish compete for their common food,
This interaction is obligatory and the zooplankton. Secondly, resources need not
always be limiting for competition to occur.
interdependent. It benefits both the In competition, the feeding efficiency of one
species. Lichens represent an intimate, species is reduced due to the interference or
mutualistic relationship between a fungus inhibitory presence of the other species, even if
and photosynthetic algae or cyanobacteria. resources (food and space) are abundant, e.g.
The most spectacular and evolutionarily Leopards do not hunt in close proximity of lion
fascinating examples of mutualism are found pride. Therefore, competition is best defined as
in plant-animal relationships. Plants need the a process in which the fitness of one species is
help of animals for pollinating their flowers significantly lower in the presence of another
and dispersing their seeds. Animals obviously species.
have to be rewarded in the form of pollen and
nectar for pollinators and juicy and nutritious
fruits for seed dispersers.

Alga

Fungus Fig. 13.8 : Co-evolution of humming birds
and plants
Lichen
Gause’s ‘Competitive Exclusion Principle’
Fig. 13.7 : V. T. S. of Lichen thallus showing states that two closely related species
Algal and fungal components competing for the same resources cannot co-
exist indefinitely and the competitively inferior
one will be eliminated eventually. This may be

302

true if resources are limiting, but not otherwise. Majority of the parasites harm the host.
In interspecific competition with sufficient They may reduce the survival, growth and
resources, species facing competition will reproduction of the host and may lead to death
evolve mechanisms that promote co-existence of the host, thus reducing its population density.
rather than exclusion. One such mechanism is They might render the host more vulnerable to
‘resource partitioning’. If two species compete predation by making it physically weak.
for the same resource, they could avoid
competition by choosing different times for Use your brain power
feeding.
1. Should an ideal parasite be able to thrive
within the host without harming it?

2. Why didn’t natural selection lead to
the evolution of such totally harmless
parasites?

Fig. 13.9 : Lion standing over dead Parasites that feed on the external surface
leopard- removing competition of the host organism are called ectoparasites.
The most familiar examples of this group are
A species whose distribution is restricted the lice on humans and ticks on dogs. Many
to a small geographical area because of the marine fish are infested with ectoparasitic
presence of a competitively superior species, is copepods. Cuscuta, a parasitic plant that is
found to expand its range when the competing commonly found growing on hedge plants, has
species is removed. lost its chlorophyll and leaves in the course of
evolution. It derives its nutrition from the host
Parasitism: plant which it parasitizes.
Parasitism has evolved in so many
Brood parasitism in birds is a fascinating
taxonomic groups from plants to higher example, in which the parasitic bird lays its
vertebrates. Many parasites have evolved to eggs in the nest of its host bird and lets the
be host-specific (they can parasitize only a host bird incubate them. During the course of
single species of host) in such a way that both evolution, the eggs of the parasitic bird have
host and the parasite tend to co-evolve, against evolved to resemble the host’s egg in size and
each other. In accordance with their life styles, colour to reduce the chances of the host bird
endoparasites evolved special adaptations detecting the foreign eggs and ejecting them
such as the loss of unnecessary sense organs, from the nest. Eggs of the parasitic bird (Asian
presence of adhesive organs or suckers to cling koel) hatch before that of its host (Common
on to the host, loss of digestive system and high Indian crow).
reproductive capacity.
Fig. 13.10 : Crow feeding Asian Koel
The life cycles of parasites are often hatching in its own nest.
complex, involving intermediate hosts or
vectors to facilitate transfer to the host. The
malarial parasite Plasmodium vivax needs
a vector (mosquito) to spread to other hosts.

303

Predation: butterfly is highly distasteful to its predator
When we think of predator and prey, most (bird) because of a special chemical present
in its body. Interestingly, the butterfly acquires
probably it is the tiger and the deer that readily this chemical during its caterpillar stage by
come to our mind, but a sparrow eating any feeding on a poisonous weed.
seed is no less a predator.
Fig. 13.11 : Adult Monarch butterfly
Although grazers are animals eating plants, displaying warning colour pattern
classified as herbivores, they are, not very For plants, herbivores are the predators.
different from predators. Predators play many Plants therefore have evolved variety of
important roles. They keep prey populations morphological and chemical defenses against
under control. Without them, prey species herbivores. Thorns (Acacia, Cactus) are
would reach very high population densities and the most common morphological means
cause ecosystem instability e.g. in absence of of defense. Many plants produce and store
frogs, locusts increase in density and destroy chemicals that make the herbivore sick. When
large tracts of agricultural lands. Biological chemicals/ produce are eaten, they inhibit
control, methods adopted in agricultural pest feeding or digestion of predator and disrupt
control are based on the ability of the predator to reproduction or even kill it. Calotropis growing
regulate prey population. Predators also help in in abandoned fields, produces highly poisonous
maintaining species diversity in a community, cardiac glycosides and that is why you never
by reducing the intensity of competition among see any cattle or goats browsing on this plant.
competing prey species. A wide variety of chemical substances that
we extract from plants on a commercial scale,
When certain exotic species are introduced (nicotine, caffeine, quinine, strychnine, opium,
accidentally or intentionally into a new etc.,) are secondary metabolites produced by
geographical area, they become invasive them actually as defences against grazers and
and start spreading rapidly due to absence browsers.
of natural predator, e. g. zebra mussels in the Commensalism:
intertidal zone of North America. This is the interaction in which one species
benefits and the other is neither harmed nor
Internet my friend benefited. An orchid growing as an epiphyte on

Name the invasive species of plants and
animals in India.

If a predator over exploits its prey, then the
prey might become extinct and following it, the
predator will also become extinct for lack of
food. This is the reason why predators in nature
are ‘prudent’.

Prey species have evolved various defenses
to reduce the impact of predation. It is a kind
of ‘evolutionary arms race’. Better camouflage
for concealment, faster speed for escape are for
the prey and the predator has to counter these,
by its own means. Some species of insects and
frogs are cryptically coloured (camouflaged)
to avoid being detected easily. The Monarch

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a branch of mango tree, will get benefit while Do you know ?
the mango tree derives no benefit. The cattle
egret and grazing cattle in close association, The instrument used to measure the hight
is a classic example of commensalism. Cattle of forest trees is called hypsometer.
egrets always forage close to cattle, as cattle
move they flush out insects that might be World Environment day - 5th June
difficult for the egrets to find and catch.
World Population day - 11th July
Another example of commensalism is
the interaction between sea anemone that has World Earth day - 22nd April
stinging tentacles and the clown fish that lives
among them. World Ozone day - 16th Saptember

The fish gets protection from predators
which stay away from the stinging tentacles.
The anemone does not appear to derive any
benefit by hosting the clown fish.

Fig. 13.12 : Commensalism- Cattle egret with buffalo and Clown fish in the tentacles of Sea
anemone

305

Activity :
Prepare chart for various interactions existing in the plant community or animal
community around you and paste the photographs of the same.

306

Exercise

Q. 1 Multiple choice questions. 3. Name the type of association:
1. Which factor of an ecosystem includes a. Clown fish and sea anemone
plants, animals and microorganisms? b. Crow feeding the hatchling of Koel
a. Biotic factor b. Abiotic factor c. Humming birds and host flowering
c. Direct factor d. Indirect factor plants

2. An assembladge of individuals of 4. What is the ecological process behind the
different species living in the same habitat biological control method of managing
and having functional interactions is with pest insects?
................
a. Biotic community Q. 3 Short answer questions.
b. Ecological niche 1. How is the dormancy of seeds different
c. Population from hibernation in animals?
d. Ecosystem
2. If a marine fish is placed in a fresh water
3. Association between sea anemone and aquarium, will it be able to survive? Give
reason.
Hermit crab in gastropod shell is that of
3. Name important defense mechanisms in
................ plants against herbivores.

a. Mutualism b. Commensalism 4. An orchid plant is growing on the branch
of mango tree. How do you describe this
c. Parasitism d. Amensalism interaction between the orchid and the
mango tree?
4. Select the statement which explains best
parasitism. 5. Distinguish between the following:
a. One species is benefited. a. Hibernation and Aestivation
b. Both the species are benefited. b. Ectotherms and Endotherms
c. One species is benefited, other is not c. Parasitism and Mutualism
affected.
d. One species is benefited, other is 6. Write a short note on
harmed. a. Adaptations of desert animals
b. Adaptations of plants to water
5. Growth of bacteria in a newlly scarcity
innoculated agar plate shows ................ c. Behavioural adaptations in animals
a. exponential growth
b. logistic growth 7. Define Population and Community.
c. Verhulst-Pearl logistic growth
d. zero growth Q. 4 Long answer questions.
1. With the help of suitable diagram describe
Q. 2 Very short answer questions. the logistic population growth curve.
1. Define the following terms : 2. Enlist and explain the important
a. Commensalism b. Parasitism characteristics of a population.
c. Camouflage
Project :
2. Give one example for each : Study the age pyramid of human population
a. Mutualism in your area
b. Interspecific competition

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14 Ecosystems and Energy flow

Can you recall? 14.1 Ecosystem :
Structure and Function :
1. What is environmental biology?
2. Meaning of the term habitat. We have already studied the various
3. Importance of ecology for humans. biotic and abiotic components of the
environment. We know that all these biotic
An ecosystem is a self regulatory and and abiotic components influence each other.
self sustaining structural and functional unit of Let us now look at these components with an
nature (biosphere). It contains both biotic and integrated approach and see how the flow of
abiotic components. Biotic components interact energy takes place in ecosystem. Interaction
with each other and also with the surrounding of biotic and abiotic components, results in
environment. Tansley (1935) coined the a physical structure that is characteristic for
term ecosystem. Ecosystems vary greatly each type of ecosystem. Identification and
in size from a small pond to large oceans or enumeration of plant and animal species of an
small farmland to village. Entire biosphere ecosystem gives its species composition.
can be considered as one global ecosystem,
made up of many local ecosystems. Since the Emergent layer
earth ecosystem is too big and too complex
to be studied, it is divided into two basic Canopy
categories, viz. terrestrial and aquatic. Forest,
grassland and desert are the types of terrestrial Understorey
ecosystems while lakes, wetlands, rivers and
estuaries are the types of aquatic ecosystems. Shrub
The ecosystems can also be classified as layer
Natural ecosystems and Artificial ecosystems.
Natural ecosystems do not require any human Fig. 14.1 : Stratification of plants in forest
inputs, in other words they are self-sustainable.
Artificial ecosystems e.g. a farm land, a fish Biotic and abiotic components differ as the
tank or even a large pond used for rearing fish, locations vary in space and time. The variation
require constant input in terms of energy or due to space results in spatial pattern. There are
materials. two types of spatial patterns. viz. Stratification
and Zonation.
In this chapter, we will study and
analyse the structure of the ecosystem, in order Vertical distribution of different species of
to appreciate the input (productivity), transfer plants and animals occupying different levels,
of energy (food chain/web, nutrient cycling) is known as stratification. For example, trees
and the output (degradation and energy loss). occupy top vertical strata or layer of a forest,
We will also look at the relationships, chains shrubs the second and herbs and grasses occupy
and webs that are created because of the energy the bottom layer. Similar stratification is also
flows within the system. observed in the open seas as epipelagic, meso-
pelagic, bathy-pelagic and benthic zones.

Find out
Stratification of animals in amazon
rain forest.

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Horizontal distribution of plants and and transport of nutrients. (minerals released
animals on land or in water, is called zonation. in decomposition process are used again by
Zonation is observed in aquatic (wetlands) as autotrophs). The energy flow is unidirectional
well as terrestrial ecosystems, but it is easily flow of energy from producers to consumers
seen at the junction of the two. Edges of a large and finally dissipation and loss as heat.
lake or beach show pronounced zonation in the
form of Inter-tidal, Littoral, Sub-littoral zones. Example- Think of a small pond ecosystem.
It is fairly a self-sustainable unit that explains
Zonation the complex interactions which exist in any
aquatic ecosystem. A pond is a shallow water
High Tide body in which all the above four aforesaid
Low Tide basic processes of an ecosystem are observed.
The abiotic component is water with all the
Subtidal Mudflats Low Marsh High Marsh dissolved inorganic and organic substances and
Channels are rich in also the rich soil deposit at the bottom of the
are important invertebrate is good supports pond. The solar input, the cycle of temperature,
habitat for fish life for habitat for pickleweed day-length and other climatic conditions
at low tide. shorebirds. cordgrass, and patches of regulate the rate of function of the entire pond.
They allow Algal mat cordgrass. A The producers include the phytoplankton,
good drainage grow here insects, good habitat algae and other aquatic plants. The consumers
and flooding also. herons and for Savannah are represented by the zooplankton, aquatic
in Mudflats. egrets and Sparrow and insects and fish. The decomposers are the fungi,
the clapper Clapper Rail bacteria located at the bottom of the pond.

rail. a. Productivity :
A constant input of solar energy is the basic
Fig. 14.2 : Zonation in wetland
requirement for any ecosystem to function
• Think about it and sustain. Productivity refers to the rate of
Why is zonation more pronounced at generation of biomass in an ecosystem. It is
expressed in units of mass per unit surface (or
the edges of habitat? volume) per unit time, for instance grams per
square metre per day (g/ m2/ day). The mass
The biotic and abiotic components of an unit may relate to dry matter or to the mass
ecosystem are all linked together to function as of carbon generated.
an ‘ecosystem unit’ through various processes
like, Productivity, Decomposition, Nutrient It can be divided into gross primary
cycling and Energy flow. In fact, these are productivity(GPP)and netprimaryproductivity
functional aspects of ecosystem. (NPP). Gross primary productivity of
an ecosystem is the rate of production of
Any ecosystem must perform these organic matter during photosynthesis. Plants
four processes for its sustainance (to be self– themselves use a considerable proportion of
sustaining). The ecosystem understudy may this GPP for their respiration. Hence, gross
be as small as a pond or entire biosphere as primary productivity minus respiratory losses
a whole. The process of productivity involves (R) constitute the net primary productivity
conversion of inorganic chemicals into organic (NPP).
material with the help of the radiant energy
of the sun by the autotrophs and consumption GPP – R = NPP
of the autotrophs by heterotrophs. The
Decomposition is the break down of dead
organic material and mineralization of the
dead matter. The nutrient cycling is the storage

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Net primary productivity is the By the process of leaching, water soluble
available biomass for the consumption, to inorganic nutrients go down (percolate) into the
heterotrophs (herbivores, carnivores and soil horizon and get precipitated as unavailable
decomposers). The annual net primary salts. Bacterial and fungal enzymes degrade
productivity of the whole biosphere is detritus into simpler inorganic substances. This
approximately 170 billion tons (dry weight) of process is called as catabolism. It is important
organic matter. Of this, the productivity of the to note that all the above steps in decomposition
oceans is only 55 billion tons. Rest of course, is operate simultaneously on the detritus.
from land based ecosystems.
A tree grows in the soil. Some are eaten by
Use your brain power herbivors. Nutrients and
energy enter food web.

What could be the reason for the low Leaves partially A leaf falls to the Some
productivity of ocean? consumed and ground. nutrients
begin to lose form leach into soil
Primary productivity (GPP) depends on the and become litter. by chemical
plant species inhabiting a particular area. It also
depends on a variety of environmental factors, action.
availability of nutrients and photosynthetic
capacity of plants. Therefore, it varies in Further
different types of ecosystems. Secondary decomposition
productivity is defined as the rate of by decomposers.
formation of new organic matter by consumers.
Alternatively, it is the rate of assimilation of Soil rich in
food energy at the level of consumers. It is the Mineralization Organic content
amount of energy available to consumer for
transfer to the next trophic level. Fig. 14.3 : Decomposition cycle

b. Decomposition : Humification and mineralization occur
Decomposers break down complex organic during decomposition in the soil. Humification
leads to accumulation of partially decomposed,
matter into inorganic substances like carbon a dark coloured, amorphous, colloidal organic
dioxide, water and nutrients, and the process substance called humus that is resistant to
is called decomposition. Dead remains of microbial action and undergoes decomposition
plants and animals, including fecal matter, at an extremely slow rate. Humus formation
constitute detritus, which is the raw material changes soil texture and increases water
for decomposition. The important steps in the holding capacity of soil.
process of decomposition are fragmentation,
leaching, catabolism, humification and Being colloidal in nature humus serves as
mineralization. a reservoir of nutrients. The humus is further
degraded by some microbes and release of
Detritivores (e.g. earthworm) break down inorganic nutrients occurs by the process
detritus into smaller fragments or particles. known as mineralisation.
This process is called fragmentation.
Decomposition as a process requires
oxygen. Temperature and soil moisture are
the most important factors that regulate
decomposition indirectly to help soil microbes.
Warm and moist environment favours
decomposition whereas low temperature and
anaerobic conditions inhibit decomposition.

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Can you recall? called consumers (heterotrophs). If they feed
directly on the plants, they are called primary
1. What is a food chain? consumers, and if the animals eat other animals
2. What are trophic levels in a food chain? which eat plants, they are called secondary
consumers. Likewise, you could have tertiary
14.2 Energy Flow : consumers too.
Sun is the only source of energy for all
The primary consumers are also known
ecosystems on the earth except for the deep-sea as herbivores. Some common herbivores are
ecosystems. Of the total incident solar radiation, insects (grasshopper, aphids), birds (parrot)
less than 50 % of it is photosynthetically active and some mammals (sheep, cattles, goat,
radiation (PAR). Plants and photosynthetic donkey) in terrestrial ecosystem and molluscs
bacteria (autotrophs) fix energy to prepare food in aquatic ecosystem. The consumers that feed
from simple inorganic materials. Plants capture on these herbivores are carnivores, (secondary
only 2-10 % of the PAR and this small amount consumers). Those animals that depend on
of energy sustains the entire living world. the primary carnivores for food are called
secondary carnivores.
Therefore, it is very important to know
how the solar energy captured by plants flows Tertiary Fourth Trophic level Examples
through different organisms of an ecosystem. Consumer (Top carnivore) Man, lion
Directly or indirectly, all organisms are
dependent for their food on producers. Hence Secondary Third trophic Birds, fish
there is unidirectional flow of energy from Consumer level (Carnivores) and wolf
sun to producers and then to consumers. The
direction can not be reversed. Energy can be Primary Second trophic Zooplankton,
used only once in the ecosystem. Consumer level (Herbivores) grasshopper

The autotrophs need a constant supply Primary and cow
of energy to synthesize the molecules they Producer
require. The autotrophs are called producers. First Trophic level Phytoplankton,
In a terrestrial ecosystem, major producers (Photoautotrophs) grass, trees
are herbaceous and woody plants. Likewise,
producers in an aquatic ecosystem are Chart 14.4 : Trophic levels
phytoplankton and algae.
You have studied several food chains
Find out and food webs that exist in nature. Food chains
are always straight and usually have four or
1. Is there any presence of living organisms five trophic levels. There are three types of food
in the perpetual darkness of deep oceanic chains viz. grazing, detritus and parasitic.
trenches? Starting from the plants (or producers) food
chains and food webs are formed such that an
2. In absence of solar radiation, what is their animal feeds on a plant or on another animal
source of energy? and in turn is food for another. The energy
trapped by the producer, is either passed on to
3. Which organisms do serve as producers in a consumer or remains trapped till the producer
the food chains of deep oceans? organism dies. Death of organism is the
beginning of the detritus food chain/web.
All animals directly or indirectly
depend on plants for their food. They are hence

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A simple grazing food chain (GFC) is Use your brain power
depicted below:

Grass Deer Leopard 1. What could be the connecting points
between the GFC and DFC?
(Producer) (Primary (Secondary
Consumer) consumer) 2. How will you classify man as carnivore
(primary/ secondary) or omnivore? Why?
The detritus food chain (DFC) begins
with dead organic matter. It is composed 3. How many trophic levels human beings
of decomposers which are heterotrophic function in a food chain?
organisms, mainly fungi and bacteria. They
meet their energy and nutrient requirements Every organism occupies a place in
by degrading the detritus. These are known as ecological community according to the source
saprotrophs. Decomposers secrete enzymes and method of obtaining its food. Organisms
that breakdown dead organic materials occupy a specific place in the food chain that is
into simple, inorganic materials, which are their trophic level. Producers belong to the first
absorbed by them. Detritus food chain may be trophic level, herbivores (primary consumer)
connected with the grazing food chain at some to the second and carnivores (secondary
levels. In a natural ecosystem, some animals consumer) to the third trophic level.
like cockroaches, crows, bears, man, etc. are
omnivores. Omnivores eat producers as well 900 Joules of 90 Joules of 9 Joules of
as consumers. These natural interconnection of energy lost to energy lost to energy lost to
food chains make it a food web. environment environment environment

1000 Joules of
Light Energy

100 Joules 10 Joules
Energy Energy

Eagle (Producer) (Herbivore) (Carnivore)

Python Fig. 14.6 : Energy loss with increasing
trophic level
Wolf Dragonfly Thrush

Rat Butterfly The amount of energy available
Frog decreases at each successive trophic level.
The number of trophic levels in any food
Fruit fly chain is restricted as the transfer of energy
follows ‘10% Law’ (R. Lindermann, 1942).
Grasshopper The law states that ‘only 10 % of the energy
is transferred to each trophic level as net
Corn A flowering plant Mangoes energy, from the previous trophic level’. In
Lavenders nature, it is possible to have different trophic
levels - producer, herbivore, primary carnivore,
Fig. 14.5 : Food web secondary carnivore, tertiary carnivore and
ultimate carnivore.

Can you tell? • Think about it
What is the maximum number of
From the given food web diagram, give
the trophic levels where the eagle is present. trophic levels in a food chain?

312

Beyond secondary carnivores, however Tertiary 4th Trophic
the amount of energy available is too less, Consumer 10 kg level
hence, there is no tertiary carnivore that feeds
exclusively on secondary carnivore, even owls
though the secondary carnivore many times will
feed on herbivores directly. This is the reason Secondary 3rd Trophic
why food chains do not exist in isolation, but Consumers 50 kg snakes level
are always interconnected to form food web
that maintains the stability of an ecosystem. Primary 100 kg mice 2nd Trophic
Consumers level
14.3 Ecological Pyramids :
Ecological pyramid is a graphic Producers 900 kg grasses 1st
Trophic
representation of the relationship between the
organisms of various successive trophic levels level
with respect to energy, biomass and number.
Fig. 14.7 : Pyramid of Biomass
Pyramid is a structure which has broader
base that gradually narrows upwards forming • Think about it
an inverted cone like structure. This concept How would you explain inverted
was developed by C. Elton in 1927.
pyramid of biomass in oceanic ecosystem?
The base of each pyramid represents the
producers or the first trophic level while the Tertiary 5
apex represents tertiary or top level consumer. consumer 5000
Any calculations of energy content, biomass, 500,000
or numbers, has to include all organisms at that Secondary
trophic level. consumers

The three ecological pyramids which are Primary
usually studied are : Pyramid of biomass, consumers
Pyramid of numbers and Pyramid of energy.
Fig. 14.8 : Pyramid of Numbers
The relative number of individuals per
unit area at different trophic levels, constitutes Similarly, pyramid of numbers can also be
the number pyramid; of biomass/ unit sometimes inverted. e.g. if we plot the number
area, is biomass pyramid and of amount of of insects on a single tree, smaller birds feeding
accumulated energy per unit area, is energy on insects, and parasites on those birds, we get
pyramid. an inverted pyramid.

In most well balanced ecosystems, all the Use your brain power
pyramids, of number, energy and biomass are
upright, i.e. producers are more in number and What will happen, if in the above
biomass than the herbivores, and herbivores example, we substitute larger bird of prey
are more in number and biomass than the feeding on small insect eating birds?
carnivores. There are exceptions to this, e.g.
oceanic ecosystem show inverted biomass
pyramid.

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Pyramid of energy is always upright, the various components of an ecosystem, is
can never be inverted, because when energy called nutrient cycling. Another name of
flows from a particular trophic level to the next nutrient cycling is biogeochemical cycle. Here,
trophic level, some energy is always lost as essential elements are cycled from abiotic to
heat at each step. In smaller food chains, more biotic world and back.
energy is available than in the longer food
chains. Types of Nutrient cycles : There are two types
of nutrient cycles viz. (a) gaseous and (b)
Tertiary sedimentary. The reservoir for gaseous type of
consumers nutrient cycle (e.g., nitrogen, carbon cycle) is
the atmosphere and for the sedimentary cycle
0.1% (e.g. phosphorus cycle) the reservoir is Earth’s
crust. The function of the reservoir is to meet
Secondary with the deficit, which occurs due to imbalance
consumers 1% in the rate of influx and efflux in any ecosystem.

Primary consumers 10% Carbon Cycle :
All life forms on earth are carbon based
Producers 100%
because carbon is the main component of
Fig. 14.9 : Pyramid of Energy all the organic compounds of protoplasm. It
There are certain limitations of constitutes 49% of dry weight of organisms. If
ecological pyramids. It assumes a simple food we look at the total quantity of global carbon,
chain, something that almost never exists in we find that 71% carbon is found dissolved in
nature. It does not accommodate a food web. oceans. This oceanic reservoir regulates the
Moreover, saprophytes are not given any place amount of carbon dioxide in the atmosphere.
in ecological pyramids even though they play a
vital role in the ecosystem. Sunlight
A given species may occupy more than
one trophic levels in the same ecosystem at Atmospheric
the same time, e.g. a sparrow is a primary CO2 Industrial
consumer when it eats seeds, fruits, peas, and commercial
a secondary consumer when it eats insects and residential
worms. Human and automotive
Photosynthesis respiration Vegetation emissions
14.4 Nutrient Cycles : plant
We have studied in earlier classes Organic respiration
carbon
that all organisms need a constant supply of
nutrients to grow, and reproduce. The amount of Organism decay Root Human uses
nutrients, such as carbon, nitrogen, phosphorus, Dead organisms and respiration
calcium, etc. present in the soil, varies in waste products
different kinds of ecosystems on a seasonal
basis. These nutrients, which are never lost Fossil fuels
from the ecosystems, are recycled indefinitely.
The movement of nutrient elements through Fig. 14.10 : Carbon cycle

Carbon that is a part of rocks and fossil
fuels like oil, coal and natural gas, has been
away from the rest of the carbon cycle for a
long time. These long-term storage places

314

are known as “sinks”. When fossil fuels are • Fossil fuels represent a reservoir of
burned, carbon that had been underground is carbon. Carbon cycling occurs through
released back into the air as carbon dioxide. atmosphere, ocean and through living and
dead organisms. Human activities have
The element carbon is a part of seawater, significantly influenced the carbon cycle.
the atmosphere, rocks such as limestone and
coal, soils, as well as all living things. • Rapid deforestation and massive burning
• Carbon as CO2 moves from the atmosphere of fossil fuel for energy and transport, have
significantly increased the rate of release of
to plants. Through the process of carbon dioxide into the atmosphere.
photosynthesis, carbon dioxide is pulled Thus, the entire carbon cycle is run
from the air to produce food.
• Carbon moves from plants to animals, by basic processes viz. Photosynthesis,
through food chains, i.e. the carbon present Respiration, Decomposition, Sedimentation
in plants moves to the animals. and Combustion.
• Carbon moves from living things to the Phosphorus Cycle :
atmosphere. Each time you exhale, you are
releasing carbon dioxide gas (CO2) into the Cyclic movement of phosphorus through
atmosphere. hydrosphere, lithosphere and biosphere
• Decomposers also contribute substantially constitutes phosphorus cycle.
to CO2 in atmosphere, by their processing of
waste materials and dead organic matter of Phosphorus is a major constituent of
land and oceans. biological membranes, nucleic acids and
• When fossil fuels burn to power factories, cellular energy transfer systems. Many animals
power plants, motor vehicles, most of the also need large quantities of this element to
carbon quickly enters the atmosphere as make shells, bones, hooves and teeth.
carbon dioxide gas. Each year, 5.5 billion
tons of carbon is released through combustion The natural reservoir of phosphorus is
of fossil fuels. Of this massive amount, 3.3 rock, which contains phosphorus in the form of
billion tons stays in the atmosphere. Most phosphates. When rocks are weathered, minute
of the remainder is dissolved in seawater amounts of these phosphates dissolve in soil
and deposited as calcium or magnesium solution and are absorbed by the roots of the
carbonate compounds which make up shells plants. Herbivores and other animals obtain
of marine animals. this element from plants. The waste products
• Burning of wood, forest fire and combustion and the dead organisms are decomposed by
of organic matter, fossil fuel and volcanic phosphate-solubilizing bacteria releasing
activity, are additional sources for releasing phosphorus. Unlike carbon cycle, there is
CO2 in the atmosphere. no respiratory release of phosphorus into
• Carbon moves from the atmosphere to the atmosphere.
oceans. The oceans and other water bodies,
absorb some carbon in the form of CO2 from There are two major differences between
the atmosphere. The carbon is dissolved into carbon and phosphorus cycle. Atmospheric
the oceanic water. Some amount of the fixed inputs of phosphorus through rainfall are much
carbon is lost to sediments and removed smaller (meagure) than carbon inputs, and
from circulation. secondly, exchanges of phosphorus between
organism and environment are negligible as
compare to carbon.

Unlike carbon and nitrogen, Phosphorus
is always in short supply and hence acts as

315

Rain

Plants Geological uplifting
Animals
Weathering of
phosphate from

rocks

Runoff

Phosphate in solution

Phosphate in Detritus settling
to bottom
soil
Leaching

Decomposers Sedimentation = new rocks

Fig. 14.11 : Phosphorus Cycle

limiting factor for the plant growth. Sudden Eventually, it leads to climax community.
influx of phosphorus in the form of agricultural Climax community does not evolve further.
runoff or industrial effluents rich in phosphate
content, leads to eutrophication in water The gradual and predictable change in the
bodies. Eutrophication is due to overgrowth species composition of a given area is called
of algae at the instance of high phosphorus ecological succession. The change is sequential
disolved in water. The overgrowth of algae and environmentally regulated.
kills or harms the aquatic life.
Process of succession involves sequential
Internet my friend steps like Nudation, Invasion, Ecesis,
Aggregation, Competition and co-action,
What are the long term and short-term Reaction and stabilization.
effects of eutrophication in water bodies?
During succession, some species colonize
14.5 Ecological Succession : an area and their populations become more
Succession : It is a spatial pattern which occurs numerous, whereas populations of other species
over the time. Time is a crucial factor. The decline and even disappear.
ecosystem is occupied by the pioneer species.
As time passes, species diversity increase The entire sequence of communities that
giving way to more complex organisms. successively change in a given area, constitute
what is called sere(s). Alternatively, it is an
entire gradient of organisms from pioneer stage
to climax stage.The individual transitional

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communities are termed seral communities. In hydrarch (hydrosere) or xerarch (xerosere),
respectively.
the successive seral stages, there is a change in
the diversity of species of organisms, increase Hydrarch succession takes place in wetter
in the number of species and organisms as well areas and the successional series progress from
as an increase in the total biomass. hydric to the mesic conditions. As against this,
xerarch succession takes place in dry areas
The present day communities in the world and the series progress from xeric to mesic
have come to be, because of succession that conditions. Hence, both hydrarch and xerarch
has occurred over millions of years since life successions lead to medium water conditions
started on earth. Succession is hence a process (mesic) – neither too dry (xeric) nor too wet
that starts where no living organisms were (hydric).
present before - like on a newly formed volcanic
island. This is called primary succession. The species that invade a bare area, are
called pioneer species. In primary succession
Other examples of areas where primary on rocks these are usually crustose lichens
succession occurs are newly cooled lava, which are able to secrete acids to dissolve
rocks and newly created pond or reservoir. The rock, helping in weathering of rocks and soil
establishment of a new biotic community is formation. These pave the way for bryophytes,
generally very slow. Before a biotic community mosses that are able to take hold in the small
of diverse organisms can become established, amount of soil.
there must be soil. Depending mostly on the
climate, it takes natural processes, several They are, with time, succeeded by
hundred to several thousand years to produce herbaceous plants, and after several more
fertile soil on bare rock. stages, ultimately a stable climax forest
community is formed. The climax community
Secondarysuccessionbeginsinareaswhere remains stable as long as the environment
natural biotic communities have been destroyed remains unchanged.
such as in abandoned farm lands, burned or cut
forests, lands that have been flooded, etc. Since In primary succession of aquatic habitat,
some soil or sediment is present, succession is (steps 1 to 7 in fig. 14.13) the pioneers are
faster than in primary succession. Description the small phytoplankton. They are replaced
of ecological succession usually focuses with time by rooted-submerged plants (e.g.
on changes in vegetation. However, these Hydrilla), rooted-floating angiosperms (e.g.
vegetational changes in turn affect food and Lotus) followed by free-floating plants (e.g.
shelter for various types of animals. Thus, as Pistia), then reed swamp (e.g. Typha), marsh-
succession proceeds, the numbers and types of meadow (e.g. Cyperus), scrub (e.g. Alnus) and
animals and decomposers also change. At any finally the trees (e.g. Quercus). The climax
time during primary or secondary succession, again would be a forest. With passage of time,
natural or human induced disturbances (fire, the water body is converted into land.
deforestation, etc.), can convert a particular
seral stage of succession to an earlier previous / In secondary succession, the species that
preceding stage. Also, such disturbances create invade depend on the condition of the soil,
new conditions that encourage some species availability of water, the environment as also
and discourage or eliminate other species. the seeds or other propagules present. Since
soil is already there, the rate of succession is
Succession of Plants : much faster and hence, climax is also reached
Based on the nature of the habitat – whether more quickly. Figure 14.14 shows the sequence
of stages 1 to 8 in a forest ecosystem after fire.
it is water (or very wetland areas) or it is on
very dry areas – succession of plants, is called

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Bare rock Lichens Small Perennial Grasses, shrubs, shade- Shade-tolerant trees
annual herbs, intolerant trees
plants, grasses
lichens

Pioneer stages Intermediate stages Climax community

Fig. 14.12 : Xerarch Succession of Plants

1 Phytoplankton stage 4 Reed-swamp stage 14.6 Ecosystem Services :
2 Submerged plant stage 5 Marsh-meadow stage Healthy ecosystems are the base for a wide

3 Submerged and free 6 Scrub stage range of economic, environmental and aesthetic
floating plant stage goods and services. The products of ecosystem
processes are named as ecosystem services,
7 Climax forest for example, healthy forest ecosystems purify
air and water, mitigate droughts and floods.
Fig. 14.13 : Hydrarch Succession of Plants
The Millennium Ecosystem Assessment
It is important to understand that succession, report 2005 defines Ecosystem services as
particularly primary succession, is a very slow benefits people obtain from ecosystems and
process, maybe requiring thousands of years identifies four categories of ecosystem services
for the climax to be reached. as follows.

Another important fact to understand is • Supporting services include services such
that all the successions whether taking place in as nutrient cycling, primary production, soil
water or on land, proceed to a similar climax formation, habitat provision and pollination
community – the mesic. maintaining balance of ecosystem.

• Provisioning services include food
(including seafood), raw materials
(including timber, skins, fuel wood), genetic
resources (including crop improvement
genes, and health care), water, medicinal
resources (including test and assay
organisms) and ornamental resources (furs,
feathers, ivory, orchids, butterflies, etc.)

• Regulating services include Carbon
sequestration, Predation regulates prey
populations, Waste decomposition and
detoxification, Purification of water and air,
and pest control.

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Forest Forest fire Severe forest fire Total nudation of forest land
2 34
1

8 76 5

Soil and herbs

Forest stage Wood land stage Shrubs Terrestrial plants

Fig. 14. 14 : Secondary succession in a forest ecosystem after fire

• Cultural services include cultural, spiritual byproduct. O2 not only purifies air but is also
and historical, recreational experiences, used for respiration by all aerobes.
science and education, and Therapeutics
(including animal assisted therapy) Pollination of plants brought about by
Following are the main ecological wind, water or other biotic agencies, is also an
important ecosystem service, without which
services : there would be no crops and no fruits.
Fixation of atmospheric CO2 and release
Though the value of all such services of
of O2 are the most important services provided biodiversity is difficult to determine, it seems
by an ecosystem. Photosynthetic activity of reasonable to think that biodiversity should
photoautotrophs sequesters carbon (in CO2 carry a hefty price tag.
form) from the atmosphere and releases O2 as a

Activity :

1. Fill in the banks in the given diagram and identity.

2. Collect information and prepare a chart of the sequential steps involved in the
ecological succession, explaining each step.

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Exercise

Q. 1 Multiple choice questions Q. 2 Very short answer question.
1. Which one of the following has the 1. Give an example of ecosystem which
largest population in a food chain? shows inverted pyramid of numbers.
a. Producers
b. Primary consumers 2. Give an example of ecosystem which
c. Secondary consumers shows inverted pyramid of biomass.
d. Decomposers
3. Which mineral acts as limiting factor for
2. The second trophic level in a lake is productivity in an aquatic ecosystem.

________________ 4. Name the reservoir and sink of carbon in
carbon cycle.
a. Phytoplankton b. Zooplankton
Q. 3 Short answer questions.
c. Benthos d. Fishes 1. Distinguish between upright and
inverted pyramid of biomass
3. Secondary consumers are __________
2. Distinguish between Food chain and
a. Herbivores b. Producers Food web.

c. Carnivores d. Autotrophs Q 4. Long answer questions.
1. Define ecological pyramids and describe
4. What is the % of photosynthetically with examples, pyramids of number and
biomass.
active radiation in the incident solar
2. What is primary productivity? Give
radiation? brief description of factors that affect
primary productivity.
a. 100% b. 50 %
3. Define decomposition and describe
c. 1-5% d. 2-10% the processes and products of
decomposition.
6. Givethetermusedtoexpressacommunity
in its final stage of succession? 4. Write important features of a
a. End community sedimentary cycle in an ecosystem.
b. Final community
c. Climax community 5. Discribe carbon cycle and add a note
d. Dark community on the impact of human activities on
carbon cycle.
7. After landslide which of the following
Project :
type of succession occurs? 1. Collect the information on the various
services offered by dense forest
a. Primary b. Secondary ecosystem.
2. Collect the information of various
c. Tertiary d. Climax types of pollinators and the impact of
human activity on them.
8. Which of the following is most often

a limiting factor of the primary

productivity in any ecosystem.

a. Carbon b. Nitrogen

c. Phosphorus d. Sulphur

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15 Biodiversity, Conservation and Environmental Issues

Can you recall? Definition of Biodiversity : It is the part of
nature which includes the differences in the
1. You have learnt about Chipko movement genes among the individuals of a species; the
and efforts of Shri. Jadav Payeng in variety and richness of all plants and animal
school. What is the importance of such species at different scales in a space - local
activities? regions, country and the world; and the types of
ecosystem, both terrestrial and aquatic, within
2. Why should we have national parks and a defined area.
sanctuaries?
The term biodiversity was actually coined
3. We have read about how Indian scientists by Walter Rosen (1982) but the term was
won the battle for patent of Turmeric and popularised by sociologist Edward Wilson to
Basmati rice. Why was gaining these describe combined diversity at all the levels of
patents essential? biological organisation.

4. What is in situ and ex situ conservation? Biodiversity that we see today, is the
outcome of over 3.5 billion of years of
Diversity is variety. This variety of life is evolutionary history mainly influenced by
called biodiversity. Biodiversity includes a vast natural processes and of late by influence of
array of species of microorganisms- viruses, humans.
algae, fungi, plants and animals occurring on
Earth, either in terrestrial or aquatic habitat In this chapter, we shall study the basic
and the ecological complexes of which they concepts of biodiversity such as levels and
are part. patterns of biodiversity, expanse, importance,
loss and conservation methods and efforts
The diversity is with respect to size undertaken.
(microscopic to macroscopic), shape, colour,
form, mode of nutrition, type of habitat, 15.1 Levels of Biodiversity:
reproduction, motility, duration of life cycle Diversity of living world can be observed
span, etc. This is actually due to the attempt
of living beings to accomodate with different at various levels, ranging from molecular
environmental conditions (like climatic, to ecosystem level. Major hierarchial and
edaphic, topographic, geographic, etc.) interrelated levels are genetic diversity, species
or situations, solely for their survival and diversity (community), and ecosystem diversity
perpetuation. In doing so, living organisms (ecological).
adapt themselves to overcome different
situations and thus develop distinct but Can you tell?
different features and that has actually lead to
the diversity in them. The diversity in features What can you say about species
become infused in the life cycle. In short, these diversity A and B?
adaptations in different environments serve as
basis for diversity. AB

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a. Genetic diversity: c. Ecological (Ecosystem) diversity:
It is the intraspecific diversity. It is the It is related to the different types

diversity in the number and types of genes of ecosystems/ habitats within a given
as well as chromosomes present in different geographical area. There are a large variety
species and also the variation in the genes and of ecosystems on Earth having their own
their alleles in the same species. It includes complement of distinctive interlinked species,
variation within a population and diversity based on the differences in the habitat. It
between populations that are associated can be described for a specific geographical
with adaptation to local conditions. Genetic region. Generally, there may be one or many
variations (e.g. allelic genes) lead to individual different types of ecosystems in a region. Thus,
differences within species. Such variations pave ecosystem diversity is very high in India while
way to evolution. They also improve chances it is quite low in Norway. In India, we can find
of continuation of species in the changing a great variety of ecosystems - deserts, rain
environmental conditions or allow the best forests, deciduous forests, estuaries, wetlands,
adapted to survive. Existence of subspecies, grasslands, etc. The Western ghats show great
races are examples of genetic diversity. Greater ecosystem diversity while regions like Ladakh
the diversity, better would be sustenance of a and Rann of Kutch do not show variance like
species. You know about 1000 varieties of we observe in Western ghats.
mangoes and 50,000 varieties of rice or wheat
in India. The diversity of life at all the three levels
is now rapidly being modified by modern
Another case of genetic diversity is : a man.
medicinal plant Rauwolfia vomitoria which
secretes active component reserpine, is found 15.2 Patterns of Biodiversity:
in different Himalayan ranges. This plant There are two patterns viz, Latitudinal
shows variations in terms of potency and
concentration of active chemical, from location and Altitudinal gradient and species-area
to location. relationship.

Genetic diversity or variability is essential Think about it
for a healthy breeding population of a species.
What are latitudes and longitudes?
b. Species diversity: Which of these imaginary lines are more
It is the interspecific diversity. The significant with reference to diversification
of living beings? Why?
number of species of plants and animals that
are present in a region, constitutes its species a. Latitudinal and altitudinal gradients :
diversity. Some areas or regions are richer Biodiversity, barring Arid/ Semiarid and
in species than in the other regions. Species
diversity deals with variety of species (species aquatic habitat, show latitudinal and altitudinal
richness) as well as number of individuals of gradient.
different species (species evenness) observed
in area under study. E.g. amphibian species Latitudinal : Ecological studies have revealed
diversity is more in western ghats than in eastern that the distribution of diversity is not uniform
ghats. Natural undisturbed tropical forests have around the Globe. Species richness exhibits
much greater species richness than monoculture latitudinal gradient for many plants and
plantation of timber plant, developed by forest animals (if not all). It has been observed that
plantation. India is one among 15 nations that species richness is high at lower latitudes and
there is a steady decline towards the poles.
are rich in species diversity.

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Factors like overall stability of tropical Species richness S = CAZ
regions for millions of years, lesser climatic Log-log scale
changes throughout the year and availability log S = log C + Z log A
of plenty of sunlight that favoured speciation.
Tropical areas have less often experienced Area
drastic disturbances like periodic glaciations
observed at poles. Such a stability over millions Fig. 15.1 : Graph showing species area
of years might have favoured speciation. relationship
Lesser migrations in tropics might have
reduced gene flow between geographically Humboldt observed that species richness does
isolated regions and favoured speciation. increase with the increase in area but upto
Scientists also have considered availability of a limit. Observe the graph for species-area
more intense sunlight, warmer temperatures relationship. For many species this curve is a
and higher annual rainfall in tropics, as factors rectangular hyperbola. If we consider S to be
responsible for bountifulness of these regions. species richness, A as area under study, C as the
In more or less constant climatic conditions Y intercept and Z as the slope of the line, this
and abundance of resources, some animals relationship can be described by the equation,
enjoy food preferences. For e.g. fruits being
available throughout the year in rain forests, log S=log C+ Z log A.
variety of frugivorous organisms is obviously On logarithmic scale this relationship is a
more as compared to the temperate regions. straight line, as observed in the figure above.
For smaller areas, value of Z ranges
In short, species richness or diversity for between 0.1 to 0.2 regardless of species or
plants and animals decreases as we move region under study.
away from equator to the poles. It is maximum But for the larger areas like the entire
in tropical rain forests e.g. Amazon rain forest continents, slopes are closer to vertical axis i.e.
(40,000 plants, 1300 birds, 427 mammals, steeper. This observation indicates that in very
3000 species). large areas, number of species found, increase
faster than the area explored.
Altitudinal : It speaks for the height from mean
sea level (MSL) upwards. Species diversity Can you tell?
is more at lower altitudes than at the heigher
altitudes. It is because at heigher altitudes, 1. What is biodiversity? Explain genetic
change in the climatic conditions and drastic diversity with suitable example.
seasonal varitations, lead to the decrease in the
species diversity. 2. Species richness goes on decreasing as
we move from equator to pole. Explain.
b. Species-Area relationships :
Scientists have tried to establish relationship Importance of species diversity to the
ecosystem:
between species diversity and the size of the
habitat. It is considered that number of species Let us now understand whether we really
present is directly proportional to the area. It need all the diversity around us. What if few
is understood that larger areas may have more species are lost permanently?
resources that can be distributed amongst the
inhabitant species. Does this always hold true?

German naturalist Alexander Von

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A community is said to be stable, if number of species that are present on earth
average biomass production remains fairly today. Though over 1.5 million species have
constant over a period of time. It should be been documented as per IUCN data (2004) so
strong enough to withstand disturbances and far, we are yet to study lot more than these. We
recover quickly. It also must be resistant to are also unaware about speciation process that
invasive species. David Tillman carried out might have continued. Most of the studies that
various field experiments and proved that have been carried out are in temperate regions.
species richness does help the stability of an
ecological community. Rich diversity leads to Tropical rain forests, the major diversity
lesser variation in biomass production over a hubs, are yet to be explored completely. Some
period of time. This is called Productivity- exorbitant numbers like existence of 20 to 50
Stability Hypothesis. million varieties have been made. But Robert
May has given convincing estimate of about
Paul Ehrlich, an ecologist from Stanford 7 million species round the globe. Observe
gave an analogy to explain significance of the given pie charts and find out the relative
diversity. It is called Rivet Popper Hypothesis. share of various plant and animal groups in the
He compared Aeroplane to ecosystem and existing knowledge of biodiversity.
the species as rivets that keep all parts of
the aeroplane together. Ofcourse, there are A. Known species of Organism
thousands of rivets needed to hold all the parts
of the aeroplane together. If each passenger Total = roughly 1,800,000 species
decides to pop even one rivet or in other words,
if one species gets extinct, initially not much of Eubacteria Protists
the turbulence will be experienced but slowly, Fungi
as number of popped rivets will increase, there
will be a serious threat to the safety of the Plants
aeroplane. Also, which rivets are removed will
also matter. Animals

Suppose, rivets at key positions such as B. Known species of Animals
the ones that bind the wings to the body of the
aeroplane, are removed, situation will become Total = roughly 1,315,378 species
serious. Thus, we can say that relationship
between diversity and well being of ecosystem Vertebrates Invertebrates
is not linear. But it is certain that loss of species 58,498 species 1,256,880 species
may not pose threat to the ecosystem only
initially. Loss of key species will certainly Fish Crustaceans
cause threat in very short span of time. It will Echinoderms
affect food chains, food web, energy flow, Amphibians Sponges
natural cycles, etc. In short it will affect the Reptiles Cnidarians
balace of ecosystem. Birds Rotifers
Flatworms
15.3 Biodiversity Current Scenario Mammals Mollusks
How many species do really exist on earth Annelid worms
Nematode worms
and how many of them are found in India? It is Arachnids
difficult to come to consensus about the exact Insects

C. Known species of Plants

Total = 287,655 species Ferns
Mosses

Flowering plants Conifers
(monocots)

Flowering plants
(dicots)

Fig. 15.2 : Graphic representation of known
animal and plant groups

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In the diagrams, we do not find any data 15.4 Loss of Biodiversity:
of prokaryotes. Several moneran species are
not cultivable under laboratory conditions. Loss of biodiversity leads to the overall
Also, conventional taxonomic methods are imbalance in the ecosystem. The chief serious
not suitable for identification of prokaryotic aspect of loss of biodiversity is extinction of
species. species. There are three types of extinction viz,
natural extinction, mass extinction and man-
India boasts a handsome share of 8.1% of made (anthropogenic) extinction.
total biodiversity wealth of the earth. One of the
12 megadiversity countries of the globe, India Damage to biodiversity takes place due to
has 2.4% of total land area of the world. We both, natural and manmade reasons. Natural
have identified around 45000 plant species and reasons include forest fires, earthquakes,
nearly double the number of animal varieties volcanic eruptions etc. Manmade reasons
from our natural wealth. If we consider May’s are habitat destruction, hunting, settlement,
estimate of global biodiversity, we have overexploitation and reclamation.
recorded only 22% of our natural wealth. This
situation underlines the need of taxonomists Major mass extinction events occured
to study the biodiversity. But major concern is between Cretaeous and Coenozoic period;
the possibility of loss of these varieties before between Triassic and Jurassic period;
we identify them because of activities like between Permian and Triassic period;
reclamation and deforestation. between Devonian and Carbaniferous period;
between Ordovician and Silurian period in
the geological time scale where plants as well
as animal groups underwent mass extinction.

Do you know ? We are aware of five mass extinctions
during various stages of history of earth (e.g.
Recently a group of naturalists proved ice age). The current loss of biodiversity is
that a lizard fromAmboli ghat of Maharashtra considered to be the Sixth extinction which
was misidentified. They proved it on the basis is progressing at an alarming rate which is
of DNA profiling as well as number of glands estimated to be 100 to 1000 times faster than
and scales present on the legs of the lizard. prehuman times. Ecologists blame this to
Earlier thought to be Hemidactylus brookii, the human intervention in natural habitats.
the lizard is now renamed as Hemidactylus They do not forget to warn that if the current
varadgirii in the honour of renowned trend continues, we might lose about 50% of
herpetologist and conservationist, Dr. Varad diversity. Loss of biodiversity in any area
Giri. They also proved that brookii variety is can lead to the decline in plant production,
not found in India. lower resilience to environmental disturbance
like flood. It may also lead to alteration in
Internet my friend environmental processes like disease cycles,
plant productivity etc.
1. Find out information about Zoological
Survey of India and Botanical Survey of Causes of Biodiversity losses:
India. There are four major causes popularly

2. You may visit Zoological Survey of India, known as, ‘The Evil Quartet’.
Pune office and find out how information
about natural wealth is conserved. i. Habitat loss and fragmentation:
It is the prime cause of destruction.

Reduction in vast natural habitats and local
degradation by pollution, create crisis situation
for the living beings. Loss of local habitat due

325

to human activities, creates threat to migratory resources which in turn causes threats to various
birds as well as those animals that need larger organisms. Can you corelate this with dirth
territories. Tropical rain forests are being lost of fish, we observe now a days? Dodo bird,
at an alarming rate. Tropical rain forest cover stellar sea cow and passenger pigeon are few
examples of extinction due to overexploitation.
has reduced from 14% to 6% over the years.

Do you know ? iii. Alien species invasion:

Great Indian Bustard alias Maldhok is When a new species gets introduced into
a critically endangered bird. It is considered any ecosystem accidentally or intentionally,
as flagship species of grasslands. We lost last there are chances that it proves harmful for
Maldhok from Maharashtra in 2018. Now this existing species. Sometimes, it can lead to
bird is found in Rajasthan and Gujrat. It is extinction of local species. In such a case, it is
an example of local extinction due to habitat called as invasive species. E.g. the carrot grass
loss and hunting. (Parthenium), Lantana and water hyacinth
(Eichhornia). Introduction of predator fish -
ii. Over-exploitation: Nile perch in Lake Victoria, proved deleterious
Basic difference between human beings for 200 local species of Cichlid fish.

and other animals is that, humans have the In India, introduction of African catfish
tendency to accumulate beyond their needs. Clarias gariepinus for aquaculture purpose has
This has resulted in the overexploitation of proved harmful to endemic catfish varieties.
One of the major reasons of such a harmful
effect of alien species is, lack of local predator.

a. Dodo bird iv. Co-extinctions:

Many a times, organisms are associated
with each other in obligatory way. In such
cases, extinction of one variety leads to loss
of associate variety from the ecosystem. e.g.,
Extinction of host fish causes extinction of
unique parasites. Coevolved plant-pollinator,
also will have such a threat.

b. Stellar sea cow We are aware of threat to diversity and
loss of species from earth. When any species
c. Passenger pigeon is totally eliminated from earth, it is called
extinct. e.g. Dinosaurs. When the number of
members of a species starts dwindling, it is said
to be endangered. The International Union for
Conservation of Nature and Natural Resources
(IUCN) maintains a Red Data Book also
known as Red List, where conservation status
of plant and animal species is recorded.

Fig. 15.3 : Examples of extinction due to
over-exploitation

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Internet my friend After a given species has been thoroughly
evaluated, it is placed into one of following
What is ballast water and how can it bring several categories.
about introduction of alien species into any 1. Extinct (EX), a designation applied to
ecosystem?
species in which the last individual has
Do you know ? died or is not recorded.
2. Extinct in the Wild (EW), a category
Many a times, we read about leopard containing those species whose members
attacks on humans or about elephants survive only in captivity
from Karnataka destroying agricultural 3. Critically Endangered (CR), a category
lands and orchards in Sindhudurg region containing those species that possess an
of Maharashtra. With increase in human extremely high risk of extinction with very
population, man started encroaching forest few surviving members (50).
land. Animals either out of sheer curiosity 4. Endangered (EN), a designation applied
(in case of young leopards) or for lack of to species that possess a very high risk of
sufficient resources, venture out from their extinction as a result of rapid population
original place. This results in Man-Animal decline of 50 to more than 70 percent over
conflict. the previous 10 years (or three generations).
5. Vulnerable (VU), a category containing
Various measures are adapted by those species that possess a very high risk
forest department to minimise this tussle. of extinction as a result of rapid population
e.g., Government not only gives monetary decline of 30 to more than 50 percent over
compensation to farmers affected by elephant the previous 10 years (or three generations).
attacks, but even the forest department 6. Near Threatened (NT), a designation
conducts community meetings to train applied to species that are close to becoming
locals to face the attack. Also, measures like threatened or may meet the criteria for
appointing experts to tame the wild elephants threatened status in the near future.
with the help of domesticated elephants, and 7. Least Concern (LC), a category containing
sensitising people towards wild life are most species that are pervasive and abundant
important part of such activities. after careful assessment
8. Data Deficient (DD), a condition applied
Do you know ? to species in which the amount of available
data related to its risk of extinction, is
The IUCN system uses a set of five lacking in some way.
quantitative criteria to assess the extinction 9. Not Evaluated (NE), a category used to
risk of a given species. These criteria are : The include any of the nearly 1.9 million species
rate of population decline; The geographic described by scientists, but not assessed by
range; Whether the species already possesses the IUCN
a small population size; Whether the species
is very small or lives in a restricted area; Can you tell?
and Whether the results of a quantitative
analysis indicate a high probability of 1. Explain how loss of species diversity can
extinction in the wild. harm ecosystem?

2. Give various categories of endangered
species explained by IUCN.

3. What do you understand by invasive
species? How does it affect local
population?

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15.5 Conservation of Biodiversity : and burn policy of locals to reclaim forestland
Conservation of biodiversity means has caused a towering 906000 hectares of
forest devastation, only in the year 2019. We
protection, upliftment and scientific the humans, need to rethink about our attitude
management of biodiversity to maintain towards nature!
its optimum level and to derive sustainable
benefits for the present and future strategies. c. Ethical reasons:
We have no right to destroy the diversity
Why to conserve Diversity?
The reasons for conservation of biodiversity simply because we share the earth with them!
All living beings have equal right to survive
can be classified into three categories: irrespective of their known or prospective
economic use.
a. Narrowly utilitarian reasons:
Since time immemorial, humans are Internet my friend

reaping material benefits from biodiversity. Visit www.gotul.org.in to find out
It may be deriving resources for basic needs information about various efforts for
such as food, clothes, shelter or industrial biodiversity conservation in Maharashtra.
products like resins, tannins, perfume base etc.
For aesthetic use as in ornaments or artefacts. How do we conserve biodiversity?
Medicinal use of plants and animals, is another Conservation means sustainable use of
major factor. It shares 25% of global medicine
market. Around 25000 species are put to use natural resources. There are two main types of
by tribals worldwide as traditional medicines. conservation strategies :
Several are yet to be explored for their potential
as medicinal plants. a. In situ conservation:
Protectionofanorganismwillautomatically
Nowadays bioprospecting of economically
important species is carried out. Bioprospecting takes place, if its natural habitat is protected.
is systematic search for development of e.g. Announcing Kanha forest as tiger reserve.
new sources of chemical compounds, genes, This is called in situ conservation. This is the
micro-organisms, macro-organisms, and other most appropriate method of conservation. It is
valuable products from nature. nothing but conservation ‘at home’. Around
34 Biodiversity hotspots have been identified
b. Broadly utilitarian reasons: by the conservationists. These are the regions
If we find out the cost of oxygen cylinder with high species richness as well as density.
These areas need to be protected strategically
and try to calculate the value of oxygen we by setting legislative measures apart from
breathe with such ease; we will understand awareness and conservation.
what nature is giving us for free! Animals play
a crucial role in pollination and seed dispersal. In situ conservation also includes
introduction of varieties traditionally
Amazon forest is estimated to produce 20% used into farming and horticulture. E.g. In
of total oxygen of earths atmosphere. We need Maharashtra, Pawra tribals in Satpuda have
to consider recreational use of diversity too. protected varieties of corn with different
coloured kernels.
You must have come across the news
about devastating fires in amazon rainforest in
August 2019.

These are mainly caused in Brazil and
are more manmade than natural. The slash

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India has three of world’s biodiversity Sacred groves serve the only chance of
hotspots (the areas with high density of survival for some endangered varieties of
biodiversity), Western ghats, Indo-Burma animal and plant species. Tribals do not allow
and Eastern-Himalayas. It has been estimated to cut even a single branch of tree from sacred
that protection of these diversity rich hotspots grove. But with the increasing lust and greed,
could reduce extinction rate by almost 30%. are sacred groves safe? We must think about it.

India, at present has 14 biosphere reserves, b. Ex situ conservation:
90 national parks and 448 wildlife sanctuaries. Sometimes when a species is critically
In Maharashtra, there are 5 national parks and
11 sanctuaries. endangered, special measures have to be under
taken to protect it. It might be protected in
Internet my friend captivity, as one of the measures of protection.
This is called Ex situ conservation. In this type
Collect the information about protected of conservation, living beings are protected
areas, biosphere reserves, national parks away from their natural habitats in special
and wild life sanctuaries. settings. Wild life safari parks, zoological
parks and botanical gardens serve this purpose.
Can you recall? Animals which have decreased in number, are
allowed to breed in captivity in order to protect
What are sacred groves? them.Eg crocodile bank of Chennai.

Indian culture and traditions are always Seed banks are established to conserve wild
connected with nature and rituals are laid varieties of food grains and vegetables. Now a
down to protect biodiversity. In many cultures, days, modern techniques like tissue culture, in
stretches of forests were set aside and protected vitro fertilization of eggs and cryopreservation
in the name of Almighty, which are called (preservation at low temperature -1960C)
sacred groves. of gametes, are used to protect endangered
species.
Such sacred groves are found in Khasi
and Jaintia hills in Meghalaya, Western ghat By now we have, thus, understood the
regions of Maharashtra and Karnataka,Aravali immense importance of biodiversity and dire
hills of Rajasthan and Bastar, and Chanda and need to protect it.
Sarguja areas of Madhya Pradesh.

Do you know ? Dr. Akira Miyawaki studied native forests of Japan especially

the old shrine groves and developed a technique of growing dense plantations in short time. It is

a technique for restoration of natural vegetation on degraded land. In this technique, after soil

testing, the landmass is dugout and soil is mixed with local biomass and humus. Plantation is

done in layers and saplings are planted close to each other. Due to this, sunlight doesn’t reach

soil retaining the moisture. Close proximity of plants leads to faster vertical growth than lateral.

Also, it promotes natural selection. Native varieties are planted and the forest develops at almost

ten times faster than the natural way. It requires a caring period of 3 years after which it grows

and develops its own diversity naturally. In India, this technique is adapted at several places

including remote districts like Chandrapur as well as metro cities like Mumbai and Bengaluru.

Though there is debate about feasibility of the technique, it is certainly helping in retaining and

recharging groundwater table, supporting local biodiversity and curbing air pollution by adding

to green cover.

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Internet my friend Know the Conservationist

Find out information about LACONES, Rahibai Popere, seed
Hyderabad. mother of Maharashtra.
Hailing from remote
15.6 Biological diversity Act 2002: village in Ahmednagar
India participated in Earth Summit, district, Rahibai runs
seed bank for 54 crops
Rio de Janeiro and is a party to Convention and 116 varieties. Crops include wild
on Biological Diversity (CBD-1992). varieties of brinjal, guava, mango, spinach,
methi, millets, pulses, hyacinth beans and
In order to provide framework for the peas. She also trains farmers and students for
sustainable management and conservation of seed selection, enhancement of soil fertility,
our country’s natural resources, government pest management and control. She is among
passed Biological Diversity Act (BD Act) in 3 Indians on BBC list of ‘100 women, 2018’.
the year 2002 in compliance with CBD. The
law broadly defines biodiversity, as plants, Can you recall?
animals and microorganisms and their parts,
their genetic materials and by-products. It 1. What is pollution? Enlist its types.
excludes value added products and human 2. Define pollutant. How are our daily
genetic material.
activities responsible for pollution?
Regulation of access to Indian biological
resources as well as scientific cataloguing of 15.7 Environmental issues:
traditional knowledge about ethnobiological Exponential growth of human population
materials, were the main objectives for
proposing this act. coupled with industrial development, has
resulted in the rampant loss of natural resources
Athree-tier system has been established with over last ten decades.
National Biodiversity Authority (NBA) at the
national level, the State Biodiversity Boards This uncontrolled exploitation of nature
(SBBs) at the state level, and Biodiversity disturbed the delicate balance between living
Management Committees (BMCs) at the and non-living components of biosphere.
local level for approval of utilization of any Utilization and production of synthetic
biological resource for commercial or research materials and construction activities have
purpose. It is mandatory for foreigners, NRIs pumped several undesired substances in
as well as Indian citizens and institutions to ecosphere. This has resulted in severe pollution.
seek permission from NBA before exploiting
local resource. NBA has powers of civil court. Noise
Not seeking approval of NBA, can incur jail pollution
and fine up to 10 lakh rupees.
Water Types Soil
Can you tell? pollution of pollution

1. Differentiate between in situ and ex situ pollutions
conservation.
Air Radioactive
2. Name any two modern methods of ex situ pollution pollution
conservation of species.

3. Write a note on BD Act 2002.

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Any substance that causes pollution, is Gaseous pollutants include CO2, CO, SO2,
called Pollutant. In order to protect and improve NO, NO2 etc.
the quality of our environment, the Government
of India has passed the Environment Protection Carbon di-oxide is a greenhouse gas.
Act 1986. In the past, levels of CO2 in the atmosphere
remained low. Due to burning of fossil fuels,
a. Air Pollution : as well as increasing deforestation the levels of
Effect of air pollution : CO2 are rising at alarming rate. Photosynthesis
process balances CO2 : O2 ratio of the air to
Respiratory surfaces of living beings a great extent. CO2 is also removed from the
are constantly interacting with air. Any air by weathering of silicate rocks forming
unfavourable alteration in air quality, affects limestone. A jet plane in a single trip across the
the respiratory system. Severity of damage Atlantic uses 35 tonnes of oxygen and releases
depends on concentration of pollutant, 70 tonnes of CO2. We are going to discuss the
duration of exposure and the organism. Even role of CO2 in global warming later in this
in case of plants, air pollution results in poor chapter.
yield of crops and premature death of plants.
Nowadays automobiles are omnipresent. They Carbon monoxide (CO) :
are major cause for atmospheric (air) pollution. It is a poisonous gas produced by
Regular maintenance of vehicles and use of
lead-free petrol or diesel can reduce pollutant incomplete combustion of fuel such as coal or
from exhausts. wood. Vehicular exhausts are the largest source
of CO.
Types of air pollutants :
Air pollutants are of two types – particulate Use your brain power

pollutants and gaseous pollutants. State the effects of CO on human body.
Particulate air pollutants may be solid
Nitrogen di oxide (NO2) and nitrogen
or liquids. Particles with diameter 10 µm may monoxide (NO):
settle in the soil but particles with 1 µm or
less remain suspended in the air. According These are released by automobiles and
to Central Pollution Control Board (CPCB), chemical industries as waste gases. NO2 when
particulate matter of size 2.5µm or less in combines with water vapours forms nitric acid.
diameter (PM2.5) are responsible for causing It causes irritation to eyes and lungs. At high
the greatest harm to humans. concentration, it causes injury to lungs, liver
and kidneys.
These fine particulates can be inhaled deep
into the lungs and are responsible for irritation, Control measures:
inflammation and damage to lungs. In addition Various ingenious mechanisms have been
to this, it causes breathing and respiratory
disorders and premature deaths. developed to control emission of gaseous and
particulate pollutants through vehicles and
Smoke, smog, pesticides, heavy metals, industries. Few examples are explained below:
dust and radioactive elements are the examples
of particulate pollutants. Electrostatic precipitator :
It is most widely used for removing
Use your brain power
particulate matter like soot and dust present in
Does particulate matter help to reduce industrial exhaust. It can remove almost 99%
atmospheric temperature? particulate matter present in exhaust from a
thermal power plant.

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Precipitator Smoke particles Catalytic converters:
Positively charged attracted to Motor vehicles equipped with catalytic
collector plates
collector plates converter should use unleaded petrol because
Negatively lead in the petrol, inactivates the catalyst.
charged
metal grid Carbon monoxide (CO) Nitrogen (N2)

Clean gas Hydrocarbons Nitrous oxide Water Carbon
stream
(HC) (Nox) (H2O) dioxide (CO2)
Gas stream containing particles Particles removed
picks up negative charge 1. Exhaust gasses 2. The exhaust gasses 3. The
enter the reduction then enter the oxidation exhaust that
Fig. 15.4 : Electrostatic precipitator block of the catalyst block of the catalyst where exits the
where the oxides
In this method, high voltage is applied hydrocarbons and the converter
and electric discharge takes place which of nitrogen react newly formed oxygen react is less
causes ionisation of air in the smokestack. forming nitrogen to form carbon dioxide. harmful.
Free electrons in the ionised air get attached and oxygen.
to the gaseous/dust particles moving up the Nox N2 CO N2 CO2
stack. These negatively charged particles
move towards the positive electrode and settle Nox O2 O2 H2O
down there. These particles are removed by CO HC
vibrations of the electrodes and collected in the
reservoir. HC

Internet my friend Fig. 15.6 : Catalytic converter

Find out information about carbon foot Controlling Vehicular Air Pollution : A case
print. Think about measures to reduce your study of Delhi
own carbon foot print.
In the year 1990, Delhi ranked fourth
Exhaust gas Scrubbers are used to clean air among 41 most polluted cities of the world.
for both dust and gases by passing it through In response to PIL (Public Interest Litigation),
dry or wet packing material. It can remove Supreme court of India sent orders to Delhi
gases like SO2. In the scrubber, the exhaust is government to take appropriate actions.
passed through a spray of water or lime.
In response, several measures were taken by
Sprayers Treated Delhi Government. By 2002, all the city buses
Flue gas were converted to run on CNG (compressed
natural gas). CNG is advantageous over other
Flue gas fuels because it is economic, burns efficiently
with SO2 and is adulteration proof fuel.

Collection Smokestack According to new fuel policy, the norms
tank SCOaS2 Osc3r·u2bHb2eOr CaO + H2O are set to reduce sulphur and aromatic content
Boiler of petrol and diesel. Another provision is
upgradation of engines. For this, Bharat
stage emission standards (BS) are set. These
standards are equivalent to Euro norms and
have evolved on similar lines as Bharat Stage
II (BS II) to BS VI from 2001 to 2017. Let us
observe how the norms have changed in the
following table 15.7

Fig. 15.5 : Exhaust gas Scrubber

332

Table 15.7 :Bharat stage emission standards

in cities of India. Do you know ?

Vehicle Norms Cities of Inspite of all the measures, New
Implementation Delhi and adjoining areas witnessed great
smog between 1st to 9th November 2016. Air
4 Bharat All metro cities pollution at this time peaked on both 2.5PM
and 10PM levels. This is reported as one of
wheelers Stage II the worst levels of air quality since 1999.

4 Bharat Throughout the country Colder weather and stagnant winds, trap
wheelers Stage III since October 2010 smoke from various sources like firecrackers,
burning crop stubbles, lit garbage and road
4 Bharat 13 mega cities (Delhi and dust. Citizens suffered breathlessness, chest
muscle contraction, irritation in eyes, asthma
wheelers Stage IV NCR, Mumbai, Kolkata, and allergy. Administration took certain
measures like closing educational institutions,
Chennai, Bengaluru, suspending of construction or demolition
work, undertaking vacuum cleaning of roads
Surat, Kanpur, Agra, etc. Even Badarpur thermal power plant was
temporarily closed down. Do you think mere
Lucknow, Solapur) since setting standards is not enough? We must
encourage means like car pooling and use of
April 2010. public transport.

2 Bharat Throughout the country Can you tell?
wheelers Stage III since October 2010
1. Describe any 2 particulate and gaseous
3 Bharat Throughout the country pollutants.

wheelers Stage III since October 2010 2. Explain various technologies used for
removing particulate matter from different
Do you know ? sources of air pollution.

Pradhan Mantri Ujjwala yojana 3. What are the ill effects of noise pollution
(Pradhan Mantri clean fuel programme) on human health?

It was launched by Prime Minister of 4. Give any norms for reducing sulphur and
India, on 1st May 2016 to distribute 50 million aromatic contents of petrol and diesel.
LPG connections to women of BPL families.
In many BPL families, chullhas are used b. Noise pollution :
where incomplete combustion of wood and In India, the Air (Prevention and control
coal leads to CO poisoning. Use of LPG helps
in reducing such household air pollution. of pollution) Act 1981, amendment 1987,
includes noise as an air pollutant. Noise is an
Have you noticed that BS V is missing in undesired high level of sound. Noise causes
above table? Note that, in 2001, Bharat stage psychological and physiological changes in
II emission norms were set for CNG and LPG human beings. There is dire need of creating
vehicles. It stipulates that emission of sulphur awareness about noise pollution caused during
be controlled at 50 ppm in diesel and 150ppm festivals and processions in our society.
in petrol. Aromatic hydrocarbons should be just
42% in concerned fuel. The aim is to reduce
sulphur emission to 50ppm in petrol and diesel
along with aromatic hydrocarbons to 35%.
Government of India directly adapted BS VI
in the year 2018, skipping BS V. These efforts
decreased the levels of CO2 and SO2 in Delhi.

333

Exposure to extremely high sound level Increased utilisation and discharge of harmful
(150 decibels or more) generated during a take- waste water in water bodies has caused severe
off of a jet plane or rocket, may damage ear pollution.
drums and cause permanent hearing loss.
Most of the water pollution is manmade.
Noise also can cause sleeplessness, Polluted water may be turbid, foul smelling,
increased heartbeat, altered breathing pattern and may contain number of pathogens, heavy
and psychological stress. Noise may negatively metals, oils etc.
interfere with child’s learning and behaviour
pattern. The common sources of noise pollution Realising the importance of maintaining
are machines, transportation, construction the cleanliness of the water bodies, Government
sites, industries etc. of India has passed the Water (prevention and
control of pollution) Act 1974 to safe guard
Activity : our water resources.

Find out different sources of noise Can you recall?
pollution in your surrounding.
1. Where does domestic waste water go in
Reduction of noise in our industries can urban and rural areas?
be brought about by use of sound absorbent
materials or by muffling the noise. Laws which 2. What is importance of sewage treatment
prohibit blowing horn in the areas of schools plant?
and hospitals, need to be implemented strictly
to curb decibel levels. Domestic sewage and Industrial Effluents:
Even a small quantity of about 0.1%
Govt. of India has rules and regulations
against firecrackers and loudspeakers. Supreme impurities in water, can make it unfit for
court of India has banned loudspeakers at human consumption. Solids are relatively easy
public gatherings after 10pm. to separate but dissolved salts such as nitrates,
phosphates, other nutrients and toxic metal ions
Internet my friend as well as organic compounds, are difficult to
remove.
We have studied about health effects of
noise pollution on humans. How does this Domestic sewage is one of the most
pollution affect birds? Does it affect marine common source of water pollution. It contains
life? Find out. biodegradable organic matter. It readily
gets decomposed by bacteria and other
Can you recall? microorganisms. They use organic matter as
substrate and utilise some amount of sewage.
1. Define water pollution.
2. When will you call a water body polluted? It is possible to estimate biodegradable
organic matter in sewage water by measuring
c. Water Pollution and its Control: Biochemical Oxygen Demand (BOD). It is
Water has been a controlling factor in the amount of dissolved oxygen required by
microorganisms for decomposing the organic
distribution and density of living beings in an matter present in water. It is expressed in
area. Human water consumption increased milligram of oxygen per litre (mg/L) of water.
many folds with increased industrialisation. High BOD indicates intense level of microbial
pollution.

334

Microorganisms involved in biodegradation Stinking eutrophic lake with coloured and turbid
of organic matter in water body consume lot water
of dissolved oxygen. This results in sharp
decline in oxygen level of water which leads Loss of species diversity
to mortality of fish and other aquatic creatures.
Death of aquatic animals including fish
Presence of large amount of nutrients in
water causes excessive growth of planktonic Reduced contents of dissolved oxygen
free-floating algae specially, blue green algae.
This is called algal bloom which gives colour Increase in organic loading of lake
to the water bodies. Algal bloom often releases
toxins in water. So, fish die due to toxicity. Death of submerged plants due to reduced
Quality of water deteriorates and becomes light
toxic for human beings and other animals.
Biological enrichment of water (algal bloom,
Another threat to aquatic ecosystem, is planktonic algae and higher plants)
water hyacinth (Eichhornia crassipes). It is
an aquatic plant, native of amazon basin, Nutrient enrichment of water
highly problematic invasive species. It was
first introduced in India for its lovely purple Fig. 15.8 : Eutrophication
coloured flowers. But, now it is a nuisance as certain pollutants get accumulated in tissues in
it grows excessively and covers entire water increasing concentration along the food chains
body. This plant grows faster than our ability (successive trophic levels) is called Biological
to remove it. It is commonly called ‘Terror of Magnification (Biomagnification)
Bengal’.
Fish-eating birds of prey
Natural Eutrophication is aging of a lake 25 ppm
due to nutrient enrichment of water. Depending
on the size of the lake, climatic conditions and Large fish
other factors, natural aging of lakes require 2 ppm
thousands of years. However, due to pollutants
from human activities like effluents from Small fish
agricultural lands, industries and homes (house 0.5 ppm
hold) have accelerated this aging process. This
phenomenon is called Cultural or Accelerated Zooplankton
Eutrophication. Observe the flow chart and
understand the process of eutrophication. 0.04 pp Water

This results in non-availability of dissolved 0.000003 ppm
oxygen for aquatic organisms. This leads to
death of fish and other aquatic organisms. Its Fig. 15.9 : Biomagnification of DDT
decomposition further depletes the dissolved
oxygen. So, a lake can literally get choked to Many of the pesticides are non-degradable.
death. So, they get accumulated in the tissues of
organisms. They neither get metabolised nor
A few substances usually present in are excreted.
industrial waste waters can undergo biological
magnification. The phenomenon through which

335

They are passed on to the next trophic When the pit of an ecosan toilet fills up, it
level. This is commonly seen in case of DDT is closed and sealed. After about 8-9 months,
and Mercury. Observe the food chain in the the faeces are completely composted to organic
given figure. It shows how biomagnification of manure.There are working EcoSan toilets in
DDT takes place. many areas of Gujrat, Kerala, Tamilnadu and
Sri Lanka.
Use your brain power
Recycling of sewage water by reverse
Why do you think the amount of DDT osmosis will help to solve the problem of not
is maximum in birds? only scarcity of water but also the disposal of
sewage water. At Tirumala hills, millions of
Thermal pollution of water is caused pilgrims visit. Every building here has R.O.
due to rise in temperature of water. The main system which solves the problem of huge
source of thermal pollution are the thermal water demand. Recycling of sewage water
and nuclear power plants. The power plants is seen in many townships in Mumbai. Rain
use water as coolant and release hot water. As water harvesting is encouraged and made
many organisms are sensitive to temperature, mandatory for new constructions by Municipal
sudden rise in temperature leads to loss of flora Corporation.
and fauna.
Can you tell?

Internet my friend 1. Explain BOD and its effects on aquatic
ecosystem.
1. Find out biomagnification of diclofenac
and DDT in birds. 2. Ecological sanitation is the need of the
day. Justify.
2. Find out various types of agrochemicals
which have ill effects on ecosystem. 3. Explain the phenomenon of biological
magnification.
Measures to reduce sewage water:
In order to conserve water and prevent Solid Waste Management :
You have already studied about solid waste
creation of sewage, ecosan is a sustainable
system for handling human excreta using dry management in ninth standard.
composting toilets. This is a practical, efficient
and cost-effective solution for human waste Can you recall?
disposal.
1. Why is it necessary to separate wet and
Ecological sanitation (Ecosan) is an approach dry garbage?
to sanitation provision which safely reuses
excreta in agriculture. It reduces the need for 2. What are the six R’s to combat solid
chemical fertilizers. waste?

Ecosan toilet is a closed system that does Solid waste is everything that goes to trash.
not need water. It is an alternative to leach pit It includes wastes from home, offices, stores,
toilets in place where water is scarce or where schools, hospitals etc. Wastes are collected
there is risk of ground water contamination. and disposed by municipality. Municipal solid
waste generally consists of paper, food, plastic,
It is based on the principle of recovery and glass, metals, rubber, leather, textile etc;
recycling of nutrients from excreta to create a
valuable resource for agriculture. Burning reduces volume of the waste.
Generally, it is not burnt to completion. So
open dumps become breeding ground for rats
and flies.

336

Sanitary landfills are substitute for open Such wastes require careful treatment and
burning dumps. Here wastes are dumped in disposal. You are aware of colour code for
depression or trench. Everyday wastes are disposal of biomedical waste.
added to this pit. Landfills get filled very
soon especially in metro cities. The amount of Irreparable computers and other electronic
garbage generated is too high. In addition to goods as well as electrical waste are known
this, there is a danger of chemicals percolating as e wastes. They are buried in landfills or
and reaching down to ground water and are completely burnt. Major part of e waste
contaminate this water source. generated by developed countries are exported
to developing countries like China, India and
All wastes can be categorised in three Pakistan. During recycling process of this
types- waste, metals like copper, iron, silicon, nickel
and gold are recovered. Developed countries
1. Bio degradable have facilities for recycling of e waste. In
2. Recyclable developing countries, manual participation
3. Non bio degradable is involved. So, workers are exposed to toxic
Our rag pickers and kabadiwallahs do substances from e waste. Treatment of e waste
a great job of separation of materials for should be carried out in environment friendly
recycling. Primary goal of all citizens should manner.
be to reduce generation of waste.
The biodegradable materials can be put You have already studied about radioactive
into deep pits in the ground and left for natural pollution.
degradation. Non biodegradable wastes have
to be disposed off. Can you recall?

Maharashtra government in a 1. What is greenhouse effect?
notification on 23rd June 2018 banned use 2. Enlist greenhouse gases.
of plastic to fight pollution caused due to 3. How do you corelate green house effect
extensive use of plastic. Ban on the use, sale,
distribution and storage of plastic material. and global warming?
Mission-Plastic Free Maharashtra :
15.8 Greenhouse effect and Global warming:
The union environment ministry has
amended rules in 2016 in order to strengthen Greenhouse effect : It is responsible for heating
the implementation of environmentally sound of earth’s surface and atmosphere. Without
management of hazardous waste in the greenhouse effect, the average temperature
country. of Earth would have been -180C rather than
It also includes ban on use of Thermocol. average of 150C.

Large amount of use of plastic can be Of the solar radiation that reaches earth,
avoided, if we inculcate the habit of carrying Clouds and gases reflect about 1/4th and absorb
cloth bags when we go for shopping and some of it. But half of total incoming radiations
strictly refusing plastic bags from the venders. reach the earth’s surface and heat it. Small
Goverment should charge high penalty/fine portion of it, is reflected back. Earth’s surface re
for the individuals not abiding by this rule. emits the heat in the form of infrared radiations.
Part of these radiations do not escape into the
Hospitals generate harmful waste that space because atmospheric gases (CO2, CH4)
contains disinfectants, harmful chemicals and absorb a major portion.
also pathogenic microorganisms.

337

Natural Greenhouse Human Enhanced
Effect Greenhouse Effect

Less heat escapes

into space SUN

CO
2

Re-radiated heat
GrAteemnohsopuhseeregasesMore heat escapes
re-emittMeodreheat

Solar radiation
SUN into space CH M4 oreNgr2Oeenhouse gases

LessOCH 4
re-emitted heat
N 2
Solar radiation
CO 2

Re-radiated heat

Fig. 15.10 : Greenhouse effect

The molecules of these gases radiate heat This rise in temperature leads to

energy and a major part of it comes back to unfavourable changes in environment and

earth’s surface. Thus reheating the earth. This resulting in odd climatic changes.(eg; EI

cycle is repeated many times. Hence CO2 and Nino effect). EI Nino effect results in melting
CH4 are commonly called greenhouse gases. of polar ice caps and Himalayan snow caps
which may be the cause for submerging of the
The atmosphere around the earth acts as coastal areas.
glass wall of a greenhouse. It absorbs solar

radiations from the sun and radiates it to Do you know ?
earth. Atmosphere prevents infrared radiations

emitted by the earth to escape into the space. In order to overcome the problem

Gases responsible for this effect are of global warming, Chewang Norphel, Ice
carbon di-oxide (CO2), Methane (CH4), Man of India has built 13 artificial glaciers.
chloroflorocarbons (CFC), Nitrous oxide (N2O) He is an Indian civil engineer from Ladakh.
and water vapours.
Norphel noticed a small stream had
Because of burning of fossil fuels in frozen solid, under the shade of a group of
industries, by automobiles, burning of poplar trees, though it flowed freely elsewhere
agricultural wastes, levels of CO2 are increasing. in his yard.
Biogas plants, paddy fields, cattle sheds add The reason for this phenomenon :
methane to atmosphere. Chloroflorocarbons
are emitted by fire extinguishers and air The flowing water was moving
conditioners. quickly to freeze while the sluggish trickle
of water beneath the trees, was slow enough
to freeze. Based on this, he created artificial

Global warming : glaciers by diverting a river into a valley,
Increase in atmospheric concentration of slowing the stream by constructing checks.

green house gases, has resulted in the heating The artificial glaciers increase the
of Earth or rise in the temperature. During ground water recharge, rejuvenating the
past century, the temperature of the Earth has spring and providing water for irrigation.
increased by 0.60C, most of it during last three He constructed them at lower elevations, so
decades. that they melt earlier expanding the growing
season.

338

Global warming can be controlled by The ozone shield has been disturbed due
reducing use of fossil fuel, improving efficiency to increased rate of ozone degradation by
of energy usage, reducing deforestation, Chlorofluorocarbon (CFC). CFCs move
planting trees and checking of human upwards and reach stratosphere. UV rays act on
population growth. them and release Cl atoms. Cl degrades ozone
releasing molecular oxygen. Cl atoms act as
Do you know ? catalyst. So they remain in the stratosphere and
continue the effect of ozone degradation. This
El Nino effect is a climate cycle in results in ozone depletion. Although it occurs
pacific ocean with global impact on weather widely in the stratosphere, the depletion is
pattern. The cycle begins when warm water particularly marked over the Antarctic region.
in the western tropical pacific ocean shifts This has resulted in formation of large area of
eastwards along the equator towards the thinned ozone layer, commonly called ozone
coast of America. Normally, this warm water hole.
pools near Indonesia and Philippines.
UV radiations of wave length shorter than
La Nina is a climatic pattern that UV-B i.e. 100-280nm are almost completely
describes the cooling of surface ocean absorbed by earth’s atmosphere, given that
waters along the tropical west coast of south the ozone layer is intact. UV-B (wavelength
America. 280-322nm) damages DNA and mutation
may occur. It causes aging of skin, damage to
15.9 Ozone depletion : skin cells and various types of skin cancers. In
Ozone is a form of oxygen.In the human eye, cornea absorbs UV-B radiations
and a high dose of UV-B causes inflammation
stratosphere, ozone is photo-dissociated and is of cornea called snow blindness, cataract
generated by absorption of short wave length etc; Such exposure may permanently damage
UV radiations. cornea.

O3 → O2 +[O] Recognising the harmful effects of ozone
O2+ [O] → UV RAYS → O3 depletion, an international treaty, known as the
Generation and dissociation of ozone are in Montreal Protocol was signed at Montreal
equilibrium leading to steady concentration of (Canada) in 1987 to control emission of ozone
ozone in the stratosphere (12 to 15 kilometers depleting substances.
from Earth’s surface in the atmosphere).
Later many more efforts have been made
This ozone layer acts as shield that absorbs and protocols have laid down definite roadmaps
UV radiations from the sun and protects separately for developing and developed
all types of life on earth. Absorption of UV countries for reducing emission of CFCs and
radiations by ozone blanket is proportional other ozone depleting chemicals.
to its thickness. Thickness is more above the
poles than at the equator. UV rays are highly Can you tell?
injurious to living organisms since DNA and
proteins of living organisms absorb UV rays 1. How pollution by domestic garbage can
and its high energy breaks the chemical bonds be controlled?
within these molecules.
2. Give effect of CFC on ozone shield.
Thickness of the ozone in a column of air 3. Give an account of possible effects of
from the ground to the top of the atmosphere is
measured as Dobson units (DU). global warming.
4. Plastic ban in Maharashtra is an essential

step. Give reason.

339

Internet my friend Reforestation is the process of restoring a
forest that once existed but was distroyed or
1. Find out more about artificial glaciers. removed at some time in past. Reforestation
2. Collect information about colour code occurs naturally in a deforested area. We
can speed up this by plantation of tree with
used for biomedical waste. due consideration to biodiversity that existed
before.
15.10 Deforestation :
Deforestation is conversion of forest area Best example of peoples participation
in reforestation is Saalumara Thimmakka,
into non-forest area. According to an estimate, an Indian environmentalist from state of
almost 40% forests are lost in the tropics and Karnataka noted for her work in planting
only 1% in temperate region. The scenario of and tending to 385 banyan trees along a 4km
deforestation is grim in India. At the beginning stretch of highway between Hulikal and Kudur.
of 20th century, forest cover was about 30% in She has also planted nearly 8000 other trees.
India. By the end of the century, it got reduced Her work has been honoured with the National
to 19.4 %. The National Forest Policy 1988 of Citizens Award of India. She was also conferred
India has recommended 33% forest cover for with Padma Shri in 2019.
the plains and 67% for the hills.
Moirangthem Loiya from Manipur
Deforestation takes place by conversion dedicated 17 years of his life to restore
of forest to agricultural land so as to feed the Punshilok forest. He left his job and took over
growing human population.Trees are cut for the task of bringing back the lost glory of
timber, firewood, for keeping cattle in farm and 300 acres forest land. He planted a variety of
for other purposes. trees like, bamboo, oak, ficus, teak, jackfruit
and magnolia. Today the forest has over 250
Slash and burn agriculture commonly varieties of plants including 25 varieties of
called Jhum Cultivation in north eastern bamboo. It is now selected as home by great
parts of India, where farmers cut down trees diversity of animals too.
of the forest and burn the plant remains. The
ash is used as fertilizer and the land is used for Can you recall?
farming and cattle grazing. After cultivation,
the area is left for several years so as to allow What is Chipko movement?
its recovery.
Case study of people’s participation in
Major Effect of Deforestation is conservation of forests.
the increased concentration of CO2 in the
atmosphere because trees hold lot of carbon in History of people’s participation in India
their biomass, are lost with deforestation. can be traced back to 1731. The ministers of
the king of Jodhpur in Rajasthan tried to cut
It leads to the loss of biodiversity due to forest to procure wood for a new palace. Local
habitat destruction, disturbs hydrologic cycle, Bishnoi community known for peaceful co-
causes soil erosion and desertification in existence with nature, opposed king’s men.
extreme cases.
A Bishnoi woman Amrita Devi hugged
Can you tell? the trees and lost her life in an attempt for
protecting the forest. Her three daughters and
1. How Jhum cultication has led to hundreds of other Bishnois too lost their lives.
deforestation in recent years?

2. Comment on deforestation status of the
world and its major effects.

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The Government of India has recently instituted The Forest Department has created a
Amrita Devi Bishnoi Wildlife protection mobile application called ‘My Plants’ to record
Award for individuals or community from details of the plantation such as numbers,
rural areas that have shown extraordinary species and location. Authorities are expected
courage and dedication in protecting wildlife. to take care of saplings in the first year i.e.,
year 2016, 2.87 crore saplings were planted.
In 1980s, realising the significance In 2017, 5.17 crore and in 2018, 15.17crore
of participation of local communities, plantation count was achieved! In the year
Government of India introduced the concept 2019, the government aimed at a phenomenal
of Joint Forest Management (JFM) so as 33 crore sapling plantation which was launched
to work closely with local communities for at Anandwan, Warora.
protecting and managing forests. In return, for
their services to the forest, the communities get The government has decided to adapt
benefit of various forest products (Fruits, gum, Japanese Miyawaki method of plantation
rubber, medicine etc.) and thus the forest can be for this project. State Forest Department and
conserved in a sustainable manner. Social Forestry Department have run successful
pilot plantation programmes using Miyawaki
15.11 Mission Harit Maharashtra : pattern in various districts like, Beed, Hingoli,
An ambitious project of planting 50 Pune, Jalgaon, Aurangabad etc.

crore trees in four years was taken up by Use your brain power
Government of Maharashtra in the year 2016.
Under this project yearly targets were given Floods in Sangli and Kolhapur in
to each district. The plantation drive is in line August 2019, were responsible for many
with National Forest Policy (NFP) which aims problems during and after the floods. Think
at maintaining 33% forest cover in the country. and enlist different types of problems faced
A 24-hour toll free helpline number 1926 by flood affected areas.
called ‘Hello Forest’ has been set up to provide
information regarding plantation, protection
and for mass awareness.

Activity :

Complete the following chart :

All species

Evaluated
Adequate data
Threatened categories

NE DD LC NT VU EN CR EW EX

Not Near Endangered Extinct in Extinct
Evaluated Threatened the wild

Increasing risk of extinction

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