COMMUNITIE S
Summative assessment
Statement of inquiry:
To achieve fairness, development must balance the needs of
current communities with the needs of future communities.
Cooked scallops ready to be served To prepare for this assessment, carr y out some research.
What methods are used to sh for scallops by dredging?
Are scallops eaten in your par t of the world and if so,
where do they come from? Find a map on the internet
of the Southern Scallop Fisher y in New Zealand and
familiarize yourself with the geography of this area.
Read ‘ What we do in the shallows’ written by Naomi Arnold:
https://www.nzgeo.com/stories/what-we-do-in-the-shallows/
A B
Ecology of scallops 3. Scallops have various predators, such as sea
C D
stars (Astropecten polyacanthus ), octopus
1. The part of the scallop that we eat is a
(Pinnoctopus cordiformis ) and blue cod
powerful muscle linking the two valves
(Parapercis colias). What is the trophic level of
of the shell. When this muscle contracts it
scallop predators?
closes the shell, squeezing out water at high
velocity and causing the scallop to make a 4. Scallops compete for food with oysters
sudden movement. What does this sudden (Tiostrea chilensis) and green-lipped mussels
movement achieve? (Perna canaliliculus). What is the trophic level
of these competitors?
A. The scallop catches its prey
5. What is the trophic level of the
B. The scallop escapes from a predator
phytoplankton on which scallops feed?
C. The scallop swims into the dredging net
6. Some sponges live attached to the outside
D. The scallop burrows into the sea bed
of scallop shells, mak ing it harder for other
Questions 2–5 relate to scallops in the Southern animals to attach. These other animals are
Scallop Fisher y and in each question the
possible answers are: larger than the sponges and can impede
the movement of the scallop. The sponge
A. Producer cannot move from place to place by itself
but is carried by the scallop to safer areas or
B. Primar y consumer
areas with more food availability. What sor t
C. Secondar y consumer
of relationship is there between the sponge
D. Ter tiar y consumer
and the scallop?
2. Scallops (Pecten novaezelandiae ) feed on
A. Competition C. Mutualism
microscopic algae oating in sea water
B. I nterac tion D. Parasitism
(phytoplankton). What is the trophic level of
7. Draw a food web that includes scallops and
scallops?
as many other organisms as possible. [4]
144
C D Harvesting a natural resource
1300
8. The graph shows the quantity of scallops
1200
(Pecten novaezelandiae ) collected from the
)snot cirtem( thgiew taem pollacs 1100
Southern Scallop Fisher y each year from 1959
1000
onwards. The sher y was closed in 1981–2. 900
800
Suggest reasons for the:
700
a) small har vest of scallops in the 1960s [2] 600
500
b) huge increase during the rst half of the
400
1970s [2]
300
c) decrease in the second half of the 200
100
1970s [2]
d) recover y in the 1980s and the high levels 0 1965 1975 1985 1995 2005 2015
1955
year
of har vesting in the 1990s [2]
Source of data: New Zealand Ministr y for Primar y Industries (2016).
e) decrease in har vest after 2001. [2]
A B
Investigating the decline in scallops
C D
9. Many causes have been suggested for the decline in scallops
since 2001:
● silt entering rivers due to agriculture and forestr y, then
being carried to sea and covering the sea bed
● changes in weather patterns and climate due to the
greenhouse eect
● intensive scallop shing by ocean-oor dredging
● disease, toxins and pollutants.
a) Choose the hypothesis that you think is most likely to have
caused the decline in scallops since 2001. Use scientic
ideas to explain your reasons for think ing that this is the
most likely cause of the decline. [3]
b) Design a scientic investigation to test whether your
chosen hypothesis is aecting scallops in the Southern
Scallop Fisher y, including how you would control the
variables and how you would collect data. [7]
A B
Ecological restoration
C D
10. a) Discuss how science can help with attempts to restore the
Southern Scallop Fisher y and protect it for the future. [4]
b) Fisher y workers in Tasman Bay, Golden Bay and other
par ts of the Southern Scallop Fisher y are keen to restar t
dredging for scallops. Write an ar ticle for them to read. Dredged and undredged areasof
Lyme Bay on the south coast of
Explain the impor tance of balancing the needs of current England. Can you tell which is
which?
communities with those of future communities. [6]
145
8 Ecosystems Key concept: Systems
Related concepts: Environment,
Interaction, Movement
Global context: Globalization and
sustainability
European starlings y in
huge ocks in the minutes
before they land and roost
overnight. Together the
starlings are less likely to be
caught by predators than if
they y alone. The ock is
a self-organized system—
nothing plans or supervises
the movements. How does this
work? Do you know any other
examples of self-organized
systems?
This trickling lter bed is used to treat
sewage at a small community in Wales.
The sewage trickles from a rotating
boom onto a bed of small stones. As it
drains down through the bed, bacteria
in a layer on the surface of the stones
break down solids in the sewage. The
bacteria form the base of food chains
in the lter bed. The liquid reaching
the bottom is usually clean enough to
be discharged into a river. The trickling
lter bed is an example of an open
system. What materials enter and
leave the system? Why are both stones
and bacteria needed in the lter bed?
146
Statement of inquiry:
The Ear th will become uninhabitable for humans and many
other organisms if we continue to damage the environment.
NASA launched the Parker Solar Probe in August 2018. The probe has heat shields, solar panels to supply
energy, propellant thrusters for changing trajectory, antennae for radio communication with Earth plus
many different sensors for collecting scientic data. The aim is to swoop closer to the Sun’s surface than
any other spacecraft has ever done and collect important data, without being damaged by the brutal
conditions. Failures in any of the components of the probe could prevent the success of the mission.
Is the probe one system with a number of subsystems, or are there separate systems within the probe?
This famous image of the Earth
was taken from Apollo 8 when it
was orbiting the moon. Pilot Jim
Lovell is quoted as saying, “The
vast loneliness … is awe-inspiring
and it makes you realize just what
you have … on Earth.”
What would you say to someone
from another planet if they asked
what we have on Earth?
147
E C O S YS T E M S
Introduction
Key concept: Systems Organisms live together in communities and interact with their
Related concepts: Environment, environment. Because of these interac tions, living organisms and
the environment operate as an ecological system. We call this an
Interaction, Movement ecosystem. Living organisms are the biotic components and all
Global context: Globalization and par ts of the non-living environment are the abiotic components.
A forest is an ecosystem. A lak e is an ecosystem. Anywhere that
sustainability organisms live sustainably has an ecosystem, so the Ear th’s sur face
is almost covered with them, from rock y mountain peaks to deep
Statement of inquiry: ocean trenches. This thin but precious layer of ecosystems is called
The Earth will become uninhabitable the ecosphere.
for humans and many other
organisms if we continue to damage Ecosystems are complex and unplanned. They seem chaotic and
the environment. disorderly, with each organism selshly tak ing what it wants from
the environment and discarding its waste produc ts. Never theless,
Three ecosystems can be ecosystems sur vive for long periods of time —they are an excellent
seen in this view: Can you example of sustainabilit y. This is because interac tions bet ween
identify them? components of the ecosystem prevent essential resources from
running out or toxic wastes from accumulating. The k ey to it is
rec ycling. Resources move from organism to organism and bet ween
organisms and the environment, in complex repeatable c ycles.
However, there is no guarantee that the natural order we see in any
ecosystem will continue. Sometimes changes cause an ecosystem
to collapse. The changes could be triggered by a shift in climate, or
the arrival of a new species, or by damage due to human activities.
Ecosystems on Ear th are sustainable and resilient only because those
that aren’t do not sur vive.
Systems are divided into two types:
● open systems: materials are able to enter and leave
● closed systems: materials do not enter or exit.
Ecosystems are open, which has advantages and disadvantages.
Leaves falling into a lak e from trees in a forest bring food and
therefore energy that organisms in the lak e can use. On the other
hand, rain may bring acid into the lak e from air pollution in industrial
areas. R ises in atmospheric carbon dioxide from human ac tivities
can also cause acidication of the water. Even in Arc tic and Antarc tic
ecosystems toxic lead is detec table from human ac tivities in the
past. No ecosystem is therefore truly independent. They are par t of
an overall global system that is threatened in many ways by current
human ac tivities.
148
900,000
800,000
)sennot( doc fo hctac latot 700,000
600,000
500,000
400,000
300,000 1992
200,000
100,000
0
1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
year
Source of data: Millennium Ecosystem Assessment The Grand Banks are
shallow seas off the coast
What are the characteristics of aquatic of Newfoundland, where
ecosystems? ocean currents combine to
create ideal conditions for
Life rst existed in the oceans and for over a billion years all ecosystems plankton to grow and provide
were aquatic, as no organisms could live on land. Water is abundant abundant food for other
on Ear th and covers more than 70% of the Ear th’s sur face. Most of this marine life. For hundreds of
is sea or ocean where sodium chloride and other salts from rock have years cod was shed in these
dissolved, mak ing the water saline. waters, but unsustainable
overshing from the 1950s
Water evaporates from the sur face of seas and oceans and then onwards led to an ecosystem
condenses, falling as rain. Rainfall on land drains downward in streams collapse. The population of
and rivers and also forms ponds and lakes. The water contains low cod was reduced by more
concentrations of salts, so is called freshwater. Thus, we can divide than 99% and it has never
recovered
aquatic ecosystems into two groups, freshwater and marine. Aquatic
ecosystems are mostly hidden from us Coral reef ecosystems can only develop close to the water
because we cannot easily see beneath the surface where sunlight penetrates and algae inside hard corals
water sur face, but they are rich and varied. can make food by photosynthesis
The depth of the water aects what type of
ecosystem there is. In shallow water plants
or algae can attach to the underlying mud
or rock, anchoring themselves to prevent
movement. Animals live among them. In
freshwater lakes where there is calm water,
oating plants can cover the sur face, creating
cooler shady conditions below. Rocky shores
can be harsh environments where organisms
have to survive destructive wave action. In
warm shallow seawater corals can grow and
reefs can develop.
149
E C O S YS T E M S
Plants and large algae do not usually exist in deeper open water.
Photosynthesis is only carried out by microscopic algae and bacteria
that live close to the sur face where sunlight can penetrate. These
organisms and the small animals that feed on them are the plankton
that drifts in seas and oceans. Large animals can swim faster than the
currents, so move through the water to feed, or avoid being fed on.
In deep water it is mostly ver y cold and it is dark because sunlight does
not penetrate. There is little oxygen in the water because it also does
not penetrate from the air and is not being made by photosynthesis.
The ecosystems here are ver y dierent from those near the sur face,
with organisms that are adapted to the conditions. Because of the
diculty of exploring deep in the oceans these ecosystems are still
relatively unk nown.
In the depths of the ocean near hydrothermal vents there are ecosystems
where no photosynthesis occurs and the only light is generated by living
organisms. Here deep ocean sh swim among giant tube worms
Setting up an ecosystem in an aquarium
✓
You do not need a special tank to set up an aquarium—a
large glass jar will do. You will need to have a balance of
organisms—an aquarium with one type of sh, plastic
plants and food added articially each day is not an
ecosystem. Visit a local pond where you have permission to
collect material. You will need buckets and
nets. Collect some mud from the bottom of the pond
and enough water to ll your aquarium. Take some water
plants and use a net to collect pond animals. Resist the
temptation to take large numbers of animals—your
ecosystem will only stay in balance if you have relatively
small numbers and no very large animals.
Collecting pondlife Put your aquarium in a place that has light but is not
too hot. The water will probably be cloudy for a time
when you have put ever ything in, because of the mud,
but it will settle. Any pondweeds with roots should be
planted in the mud. When the water is clear you can
see what organisms there are. I f you have done a good
job, the aquarium should remain in balance for as long
as you keep it. When you have learned as much as you
can, return the water and all the organisms to the pond
where you got them—remember, this ecosystem needs
to stay in balance.
Extension activity : You could put probes in the water and use a data-logger to monitor the temperature and
pH of the water in your aquarium ecosystem.
150
What are the components of terrestrial C
ecosystems? B
A
Terrestrial ecosystems are those that are on land rather than in water.
The environment in terrestrial ecosystems is a complex mixture of Terrestrial ecosystems
solids, liquid and gases.
are those on land.
Air is a mixture of gases. I t supplies organisms in terrestrial ecosystems
with vital resources— oxygen, carbon dioxide and, in some bacteria, Aquatic ecosystems are
nitrogen. All organisms release waste gases into the air, including those in water.
methane from some bacteria. Winds move the air between ecosystems.
For this reason, all ecosystems are interconnected via the atmosphere Minerals are inorganic
and if humans change the atmosphere it aects all ecosystems. substances in water, soil
or rock, that are sources of
Water is liquid in most terrestrial ecosystems, so is also is free to move. elements essential to life.
Water from rainfall drains into the soil though spaces between the solid
par ticles. I t can then drain out of the soil into streams and rivers. In Drainage is the movement
some dr y ecosystems with little rainfall, water is drawn up through the of water through soil into
soil from underground reser ves and evaporates from the soil sur face. streams and onwards
Water changes state when it evaporates from soil or from plant towards the sea.
leaves, and water vapor in the air condenses to form dew in cool
conditions.
air air Forests, shrubland and
h shrubs grassland are open systems
llafniar wind because materials are free
erb llafniar to move in and out of the
s trees ecosystem. Animals, sunlight
and heat transfer are not
shown on this simplied
diagram
soil soil
underlying
bedrock
or sediments
key oxygen released by plants
CO absorbed by plants
2
water evaporating from plants (transpiration) or from soil
Soil is an important part of most terrestrial ecosystems. The solids within
it are dead matter from organisms and fragments eroded from rock.
These solids attract and hold both water and mineral nutrients. Unless
waterlogged, soil has air spaces that contain the same gases as the air
above the soil. However, soil usually contains less oxygen and more
carbon dioxide, due to respiration by the organisms living in the soil.
151
E C O S YS T E M S
Soil does not usually move much and in natural ecosystems it tends
to become deeper and deeper. Soil erosion can sometimes occur as
a result of wind or water movements. This can occur naturally (during
storms, for example), but is often a consequence of human activity
(after deforestation, for example).
Plants gain a stable anchorage by being rooted in soil and therefore
the whole plant does not move. Plants obtain water and mineral
nutrients from the soil. Many animals live in soil, such as ear thworms,
springtails and mites.
There are also vast numbers of bac teria and fungi, many of which ac t
as decomposers, break ing down dead matter from organisms and
releasing mineral nutrients back into the soil.
Finding animals that live in soil Visit a forest or another local
ecosystem. Obtain a sample
✓ of soil, including any organic
matter on the soil sur face,
Earthworms feed on dead matter from organisms in the soil, such as dead such as dead leaves. You
roots or leaves could use a trowel or small
spade to dig out the sample.
Put it in a tray or bowl and
sort through to nd any
living organisms present. Tr y
to identify each organism
that you nd in the soil and
then return it to its habitat.
Bacteria will be present in
huge numbers but they are
microscopic and therefore
invisible. Can you nd any
thread-like fungal hyphae?
What is the link between ecosystems
and climate?
There are many dierent types of terrestrial ecosystem. The map on the
following page shows natural ecosystem types in North America. It was
produced by the Commission for Environmental Cooperation. Study the
distribution of ecosystem types. There is a huge range, including many
dierent types of forest.
152
Is rainfall or temperature more impor tant in deciding what type of
ecosystem there is in an area? You can tr y to decide this by comparing
the ecosystems map with maps for annual precipitation (rainfall and
snowfall) and for annual mean (average) temperature. You can nd
maps of temperature and precipation for Nor th America at the CEC
website (www.cec.org/map/climate).
Polar
Boreal mo untain sy ste m
Boreal tu ndra woo dla nd
Boreal coni fe ro us fo re st
Tem perate mou ntain sys tem
Tem perate desert
Tem perate ste ppe
Tem perate contin ental forest
Tem perate ocean ic forest
Subtropi cal m ou nta in system
Subtropical d esert
Subtropi cal s tep pe
Subtropi cal d ry forest
Subtropi cal h um id forest
Trop ica l mo untai n syste m
Trop ica l dry fores t
Trop ica l mo ist fo re st
Trop ica l rain fores t
Wa t e r
No data
0 250 500 1,000 km
153
E C O S YS T E M S
What types of organism are there in ecosystems?
There are three main types of organism in ecosystems—producers,
decomposers and consumers.
Producers Decomposers
These are the organisms that can build up These break down dead organic matter.
complex carbon compounds from much This could be whole dead animals or plants,
simpler substances, such as water and carbon dead par ts of organisms such as fallen leaves,
dioxide. They take these substances fromthe a dead branch on a tree, or animal feces.
environment. They also need a source of energy, Decomposers release simple substances such
which is usually light. The main waste product as carbon dioxide back into the environment.
that they release is oxygen. All other organisms Without decomposers, dead organic matter
rely, directly or indirectly, on the complex would accumulate in an ecosystem and the
carbon compounds made by producers and simple substances required by producers
many organisms also rely on the oxygen. would run out.
Types of producer: Types of decomposer:
plants and also algae and cer tain microbes which are either bacteria or
bacteria. fungi.
Producers and decomposers rely on each other.
Decomposers need the complex carbon compounds
that producers make and producers need the simple
compounds that decomposers release. We could
imagine an ecosystem with only these two groups of
organisms. In real ecosystems there is always another
group.
Producers, consumers and decomposers Consumers
are all involved in the production of food
for humans. What examples can you see These eat material from other organisms and digest
in these photos? it in their gut or another structure inside their body.
Many consumers eat living organisms, for example
154 when an elephant feeds on the leaves of a tree,
a tick feeds on human blood, or a baleen whale
swallows k rill. Some consumers eat dead organisms,
such as a vulture feeding on carrion or an insect
lar va boring holes as it feeds on the dead wood
of a tree. These examples also show that some
consumers eat a whole organism and others just
consume par t of an organism.
Types of consumer: animals and also cer tain protozoa.
How does a decomposer feed and grow? Is the fungus on these
tomatoes a decomposer?
Decomposers need a supply of dead material from other living
organisms—this is their food. It could be dead plants and animals, feces
or even crude oil spilt from a tanker.
Decomposers release digestive enz ymes into their food. For example,
decomposers that feed on dead wood release enz ymes to digest the
two main chemicals in it: cellulose and lignin. Each type of decomposer
is adapted to break down a par ticular type of dead material and releases
the enz ymes that are needed to do this.
Decomposers are either fungi or bacteria. Bacteria are unicellular, often
with spherical or rod-shaped cells. Many of them can move through
uids, which means they can swim to their food supply. Most fungi have
a body made of thread-like hyphae, which grow over a food supply or
into it.
Enz ymes released by decomposers move through the food, digesting
it as they go. Water is needed both for the movement and for digestion.
Therefore dr y materials do not decompose. Decomposers absorb as
many of the useful products of digestion as they can, but inevitably
other organisms absorb some of them. Many fungal decomposers
release antibiotics to k ill bacteria that might absorb digested foods.
Once absorbed by decomposers, the products of digestion can be
used. Amino acids are made into proteins. They can also be conver ted
to sugars by removing a nitrogen-containing par t of the amino
acid. This par t is changed into ammonia (NH ) and released into the
3
environment.
The release of ammonia is an example of an impor tant Element How released
activity of decomposers— complex compounds made by
other organisms are broken down and simple substances carbon carbon dioxide (CO )
are released as waste products. As a result, elements that 2
producers have taken in from the environment are returned
to it. Decomposers therefore play a ver y impor tant role in hydrogen water (H O)
ecosystems. The table shows the form in which the dierent 2
elements are released.
oxygen CO and H O
2 2
nitrogen ammonia (NH )
3
phosphorus 3-
phosphate ions (PO )
4
sulfur 2-
sulfate ions (SO )
4
1. The elements in the table are all non-metals. Which
metallic elements are released during decomposition?
2. Some elements are released as par t of molecules and some as ions. What is the dierence
between an ion and a molecule?
3. If supplies of an element run out in an ecosystem, can living organisms make more by
conver ting another element?
155
E C O S YS T E M S
Researching wetlands
✓
Research these questions to nd
out more about wetlands.
1. What prevents dead organic
matter from decomposing in
some wetlands, and peat to
accumulate?
2. How do producers in
wetlands such the Venus y
trap obtain nitrogen, despite
the lack of nutrient rec ycling?
The raft spider can walk over the surface of the water in bogs, 3. What causes peat to
hunting for insects to catch decompose ver y quick ly
when it is added to soils in
gardens?
4. What are the consequences of draining wetlands, for organisms such as this raft spider, and for
atmospheric carbon dioxide concentrations?
A B
C D Experiment
Decomposing tea bags
Tea bags can be used to investigate rates of decomposition as a par t Burying a tea bag in the
of the global carbon cycle. An international organization called the Tea Ethabuka reserve in an
Bag Index ( TBI) has been coordinating this research and has collected Australian desert
results from around the world. You can nd out more about it from the
teatime4science website. TBI has developed a standard method, which Drying tea bags
scientists call a protocol. If ever yone follows this protocol then results can
be compared, because the only variables in the experiment are the ones
being investigated.
Questions
1. What types of tea bag are used? ( You will have to look at the
teatime4science website to answer this.)
2. Why are these types of tea bag chosen for the investigation?
3. Why would tea bags with a bag that can decompose be unsuitable?
The tea bags are weighed while they are still dr y and unused. They are
then buried 80 mm deep in soil and left for 90 days. They are then dug up.
As much soil as possible is removed from the outside of the tea bags and
they are dried. The tea is then removed from the bags and weighed.
4. How could you dr y out the tea bag?
5. Why is it necessar y to dr y out the tea bag?
6. Why is the tea removed from the bag before being weighed?
156
7. Why would it be better to bur y more than one bag at each location investigated?
8. How can you tell how fast the tea decomposed from the results?
9. If you buried tea bags in a deser t and in a tropical rainforest, where would you expect faster
decomposition? Explain your reasons.
10. Make another prediction about how fast dead matter from organisms decomposes. How could you test
your prediction using tea bags?
Why must carbon be recycled?
Carbon is a central part of all of the main biochemicals, but
it is not a very common element on Earth. Fewer than two
in a thousand atoms are carbon. If plants are in sunny and
warm conditions, the rate at which they can make food
by photosynthesis is often limited by the concentration of
carbon dioxide in the air—close to 400 parts per million or
0.04%. Carbon must therefore be endlessly recycled to avoid
it running out.
Carbon exists in many forms in ecosystems.
● The main inorganic reser ve of the element is carbon
dioxide, either as a gas in the air or dissolved in water.
● Living organisms contain a huge range of carbon
compounds including carbohydrates, proteins
and lipids.
● Dead matter such as fallen leaves and animal feces
contains many dierent carbon compounds.
The two main processes in the carbon cycle are
photosynthesis and respiration.
● Carbon dioxide is conver ted to carbon compounds
in photosynthesis. Sucrose, also known as table sugar, is a
carbon compound. Its chemical structure is
● Carbon compounds are conver ted to carbon pictured here
dioxide in respiration.
respiration Carbon dioxide in the photosynthesis
air or dissolved in water 157
Carbon compounds in
living organisms
E C O S YS T E M S
Mauna Loa and CO concentrations
2
412
MAY JUN
APR
410
MAR
JUL
FEB
noillim rep strap JAN
408
JUL
DEC
406
NOV
AUG
OCT
404 SEP
402 daily means
J weekly means
monthly means
A S O N D J F M A M J J A S
The carbon dioxide concentration of the atmosphere uctuates during the year. The graph shows the
concentrations during a recent year at Mauna Loa on Hawaii
1. During which months did the carbon dioxide concentration of the air a) rise b) fall?
2. The rises and falls in carbon dioxide concentration are mainly due to photosynthesis and respiration.
During which months was there
a) more photosynthesis than respiration
b) more respiration than photosynthesis?
3. What factors could cause the amount of photosynthesis to rise or fall during the year?
4. The data in the graph was collected by carbon dioxide monitors at Mauna Loa Obser vator y, which is
3,397meters above sea level on the slopes of a volcano.
a) What are the advantages of monitoring carbon dioxide at high altitude on an island in the Pacic Ocean?
b) What are the disadvantages of monitoring carbon dioxide on a volcano?
How is carbon recycled?
Respiration occurs in all organisms, but photosynthesis only occurs
in producers. Instead of taking in carbon dioxide from air or water,
consumers and decomposers obtain complex carbon compounds from
other organisms. Movement of carbon compounds from one organism to
another is therefore part of the carbon cycle. It happens when a consumer
eats another organism or a decomposer breaks down dead matter.
158
Carbon compounds Carbon dioxide in Key to arrows in the
in decomposers air or water carbon cycle diagram
Carbon compounds photosynthesis
in producers respiration
feeding
decomposition
death and
defecation
Key to carbon reser ves
abiotic
biotic
Carbon compounds Carbon compounds
in dead matter in consumers
1. Which groups of organism release carbon dioxide from respiration?
2. Deduce which arrow shows carnivores feeding.
3. Tr y to nd an example for each of the arrows on the carbon cycle.
4. Discuss what sequence of arrows a carbon atom would pass
through if it:
a) was taken in by the leaf of a hickor y tree and used to make
C
B
A
Biotic components are
glucose, which was moved to the root of the tree and used in
the living organisms in an
respiration.
ecosystem.
b) became par t of the wood in the trunk of an oak tree and a
long-horned beetle lar va ate the wood and was then eaten by Abiotic components are
the non-living parts of an
a woodpecker which used the carbon compounds from it in ecosystem.
respiration.
c) was in cattle feces used to grow mushrooms, which were eaten
by a person, who respired and released carbon dioxide, which
was used in photosynthesis by grass, which was eaten by a cow.
5. Imagine some other sequences of moves that a carbon atom could
make, by which the atom ends up back where it star ted. You could
tr y to think of a sequence that takes as long a time or as shor t a
time as possible to be completed.
159
E C O S YS T E M S
What is causing carbon dioxide concentrations
in the atmosphere to rise?
During the Carboniferous era, huge tree ferns and other plants
absorbed carbon dioxide from the atmosphere and used it in
photosynthesis. Some of the forests that grew were k illed by rising
sea levels and buried under deposits of mud. The plants did not
decompose fully and were conver ted to coal. Carbon atoms have
remained trapped in this coal for 300 million years. In a similar way,
carbon from plankton in the marine ecosystems was trapped in rock as
oil and natural gas, for example in the Permian basin of Texas, formed
over 260 million years ago.
Coal, oil and gas are k nown as carbon sinks, because they can hold
carbon taken from the atmosphere for an indenite length of time.
Carbon in coal is iner t and organisms cannot use it. Carbon in oil and
gas reser ves cannot be used by organisms either, because of a lack of
oxygen in the rocks where they occur.
Huge quantities of carbon have accumulated in these sinks, but we
are now releasing it. When coal, oil and gas are burned, carbon atoms
that have been trapped in rock for hundreds of millions of years are
returned to the atmosphere as carbon dioxide. The amount of fossil
fuel burning star ted to rise during the industrial revolution. Before this,
in the late 18th centur y, the atmospheric carbon dioxide concentration
was only 280 par ts per million (ppm). Data from Mauna Loa shows that
it is now over 400 ppm.
1. Describe the changes
in atmospheric carbon
dioxide concentration
since 1958.
2. Discuss what is likely to
happen to carbon dioxide
concentrations during the
rest of the 21st centur y.
3. Explain what has caused
the rise in carbon dioxide
concentrations.
160
)noillim rep st rap( 400 L TAAtmospheric carbon dioxide
380 concentrations have been monitored
360 at an observatory high on Mauna
Loa, a volcano in Hawaii, since 1958.
The red curve includes seasonal
uctuations and the black curve is
the change year-on-year with the
uctuations removed
Reflective skills
2
OC 340 Consider ethical,
cultural and
320 environmental
implications
1960 1970 1980 1990 2000 2010 2020
year IB students are encouraged to
reect on the implications of
Scientists are concerned that there could be ver y rapid and what they have learned. The
uncontrollable rises in atmospheric carbon dioxide concentration implications of rising carbon
during the 21st centur y, even if we reduce the amount of fossil fuels dioxide concentrations are
burnt. This is because some of the carbon dioxide released into the potentially enormous.
atmosphere by burning fossil fuels in the past was absorbed by
oceans, forests and soils but it might be returned to the atmosphere The environmental
in the future. A vicious cycle of cause and eect could develop that implications are obvious but
would threaten all of the world’s ecosystems. This is shown in the are there also ethical and
ow char t. cultural implications?
On reection, how do you
think we should be responding
to what is increasingly being
called the climate emergency?
Rising atmospheric CO concentrations
2
cause global warming as a result of the
greenhouse eect
Warming of the oceans will make CO
2
less soluble, so dissolved CO will be
2
released into the atmosphere
Hotter climates will cause forests to
change to grassland or deser t, so
biomass is reduced, with release of CO
2
Melting permafrost in the Arctic allows
decomposers to break down peat and
other dead matter thereby releasing CO
2
161
E C O S YS T E M S
I t is not clear what global temperatures might cause this vicious c ycle
to begin and it is possible that it already has. Scientists refer to it as
a tipping point, beyond which the Ear th’s ecosystems release rather
than absorb carbon dioxide. “ These tipping elements can potentially
ac t lik e a row of dominoes,” said Professor Johan Rockstrom, Executive
Direc tor of the Stock holm Resilience Centre. “Once one is pushed
over, it pushes Ear th towards another. I t may be ver y dicult or
impossible to stop the whole row of dominoes from tumbling over.
This cascade of events may tip the entire Ear th system into a new
mode of operation.”
With record high temperatures in many par ts of the world in the
summer of 2018 and widespread forest res, concerns about the
Ear th reaching tipping points led to news headlines such as “Ear th
at risk of entering ‘hothouse’ state from which there is no return,
scientists warn”.
4. I n a hothouse state, the average temperatures on Ear th could
be up to 6°C higher than they were at the star t of the industrial
revolution. What problems would this cause to ecosystems and to
humans?
5. A rise of 6°C would cause sea levels to rise by about 60 meters.
a) What are the reasons for sea level rises when the Ear th’s
temperature rises?
Rising global temperatures b) What problems would a 60-meter rise in sea level cause to
are causing Arctic ice to
melt, depriving polar bears of ecosystems including coral reefs and mangrove swamps, and
their hunting grounds
what problems would it cause to humans?
6. To tr y to prevent
a hothouse Ear th
developing, what should
be done by :
a) individual people
b) governments of
individual countries
c) international
organizations?
162
Summative assessment
Statement of inquiry:
The Ear th will become uninhabitable for humans and many other
organisms if we continue to damage the environment.
A B
Ear thwatch
C D
The following extract is par t of an online document produced by
Ear thwatch Europe, for par ticipants in an ongoing research project
at Wytham Woods near Oxford (Nor thwest Europe). Read the text and
then answer the questions that follow.
As an Ear thwatch par ticipant, you will spend time each day compounds stored in forest soils, releasing carbon dioxide
assisting scientists with data collection. Some of this work back into the atmosphere. If decomposition outpaces tree
will be repetitive, but it is fundamental to our scientic growth, then these forests will paradoxically increase the
understanding of nature. Ecosystems are incredibly carbon dioxide concentration of the atmosphere.
complex. The only way to begin to unravel this complexity Logging can increase forest susceptibility to the droughts
is by designing good experiments, and carefully collecting that are expected to become more frequent in many
as much data as possible. Without the work of thousands regions under climate change. Droughts make forests
of dedicated scientists, we would k now nothing about ammable, and large areas of tropical forests have burned
climate change, the eects of pollution, the extinction during droughts in recent years. More subtle per turbations
of species, or how to nd cures for diseases and improve of the ecological interactions among trees, herbivores,
crops. This is your chance to be par t of the scientic eor t, predators, parasites and diseases are also likely to alter the
to nd solutions to pressing environmental and cultural structure and functioning of the world’s forests.
problems, and to enjoy the beauty and diversity of nature
as you work. There is a need for research and better understanding of
the likely impacts of climate change on forest ecosystems,
Forests hold more carbon in trees and soils than any other biodiversity, biomass production, and ultimately the
terrestrial habitat. Climate change and elevated carbon implications to the local communities and the economy.
dioxide in the atmosphere will increase the growth of The main goal of our research programme is to develop a
trees that live in colder climates, thereby capturing more better understanding of the role that disturbed forests, i.e.
carbon. However, climate change will also increase the those modied by humans, play in the carbon cycle, and
activity of the bacteria and fungi that break down carbon how this could be inuenced by future climate change.
1. Explain the impor tance of the work of scientists for humans and all
other organisms on Ear th. [5]
2. The par ticipants in this research project in 2018 were people who
worked for a major oil company. Discuss the reasons for an oil company
wanting its workers to be par t of the research. [5]
3. Explain how planting a forest in an area that has been deforested could
help reduce the carbon dioxide concentration of the atmosphere. [3]
4. Explain how the spread of tree diseases could increase the carbon
dioxide concentration of the atmosphere. [2]
163
E C O S YS T E M S
A B
Analyzing oak tree growth
C D
A small sample of data from the Ear thwatch research project at Wytham
Woods is shown in the table below. I t shows the initial diameter of the
trunks of ten oak trees and increases in trunk circumference in 2010,
2011 and 2012. In 2010 there was cold weather in spring and then high
temperatures and drought conditions in the summer.
Tree number 2424 2399 2111 2446 2323 2174 2443 322 2422 2363
Initial diameter (cm) 107 69 64 49 47 39 34 31 29 20
April 2010 0 0 0 0 0 0 0 0 0 0
July 2010 7.87 1.34 0.9 7.91 1.06 1.87 5.25 2.84 0.95 0
October 2010 8.47 3.18 1.24 10.17 2.4 2.88 6.28 2.14 1.31 1.11
April 2011 3.47 2.3 1.71
Cumulative July 2011 10.82 6.07 1.14 10.22 4.81 3.56 6.44 0.88 0 0.41
increase October 2011 13.4 7.69 4.34
in trunk April 2012 15.74 8.67 0.91 18.5 6.1 6.42 11.14 1.6 1.3 1.09
circumference
(mm) 2.2 20.65 6.35 12.9 2.34 1.13 1.38
3.59 22.61 8.54 13.7 1.5 1.54 2.45
July 2012 27.81 13.83 3.6 38.08 10.88 15.3 28.17 3.11 3.74 3.45
October 2012 32.41 15.97 3.31 43.85 12.31 18.52 33.29 3.7 3.86 4.71
5. Develop a hypothesis about the growth of trees in Wytham Woods and
use the data to evaluate the validity of the hypothesis. [10]
● Process the data by using whatever mathematical procedures you
decide are suitable.
● Choose a suitable table, chart or graph to display the transformed data.
● Interpret the data and explain it using scientic reasoning.
● Evaluate your hypothesis, using evidence from the data.
The carbon dioxide concentration of the Ear th’s atmosphere has already
risen from about 280 par ts per million (ppm) to more than 400. I t is
forecast to rise to 550 ppm by 2050. To investigate the eects of this on
forests, a series of experiments are being done around the world. These
are FACE experiments (Free -Air Carbon dioxide Enrichment). The rst
was star ted in a eucalyptus forest in Australia (EucFACE) and the second
in an oak forest in England (BIFoR FACE).
A circle of steel towers forms the
edge of a FACE experimental area.
Carbon dioxide is released from holes
in the black vertical pipes that are
supported by these towers. Carbon
dioxide concentration is monitored
by sensors on the central tower
164
A B
FACE experiments
C D
A circle of towers is used to release carbon dioxide into the air. Whichever
way the wind is blowing the CO is released so that it blows into the circular
2
experimental area rather than immediately away from it. Monitors check
that the concentration is close to 550 ppm—the rate of CO release is
2
adjusted if it is not.
6. Far more CO has to be released in FACE experiments on windy days
2
than on calm days. Explain the reasons for this. [2]
7. Less CO would have to be released if the circular experimental
2
areas were enclosed with glass, but then it would not be a free -air
experiment. Explain the disadvantages of doing the experiment in This map shows the layout of one of
the experimental areas. The towers
enclosed forest. [3] cannot be in an exact circle as they
have to be positioned between the
8. Explain the reasons for think ing that the oak trees will grow faster trunks and major branches of
the trees
and store more carbon if atmospheric CO concentration rises to
165
2
550 ppm. [3]
9. Suggest a way of
measuring whether the
oak trees are growing
faster and storing more
carbon with a higher
atmospheric carbon
dioxide concentration. [2]
The growth of trees does
not only depend on
CO —it is also aected by
2
the amounts of mineral
nutrients in the soil. Some
scientists think that forest
won’t grow faster and
store more carbon with
higher CO concentrations
2
because trees will run shor t
of mineral nutrients such
as nitrate and phosphate.
10. Design a FACE experiment
to investigate whether
shor tage of mineral
nutrients will prevent
forests from storing more
carbon in the future
when atmospheric CO
2
concentrations are much
higher than they are
now. [5]
9 Evolution Key concept: Change
Related concepts: Environment,
Evidence, Transformation
Global context: Orientation in space
and time
The French artist Odilon Redon
created some disturbing
images of metamorphosis
in Origines, a series of
lithographs. In his 1903
painting Flower Clouds, shown
here, two gures look into the
distance at the sea and the
sky. What forms are appearing
there?
These pages are from The Tale
of Genji, written by Murasaki
Shikibu in the 11th century. It is
considered to be a masterpiece
and perhaps the rst example of a
novel. It is hard for modern readers
to understand the text unless
translated, because the Japanese
language has changed so much
over the last thousand years. Can
we expect the quality of novels to
have improved over the centuries
or are works from all ages just as
great?
166
Statement of inquiry:
Evidence of past changes helps us understand life today
and how it might be transformed in future.
Many movies have been based on novels. To Kill a Mockingbird is highly
regarded both in the original novel by Harper Lee and the movie adaptation
in 1962, directed by Robert Mulligan and starring Gregory Peck. Can
you think of any movie adaptations that you think are better than the
novel? Which great novels became box-ofce ops as movies? What other
adaptations of one art-form to another are possible?
Fashion can change rapidly. One possible reason is teenagers not wanting to
look like their parents. Are there other reasons for such changes in clothes,
shoes or hairstyles? Can you identify the decade when this photo was taken?
What styles of jeans are fashionable now? What style of jeans do you think
will be fashionable in, for example 30 years?
167
E VOLUTION
Key concept: Change Introduction
Related concepts: Environment,
Charles Dar win’s book On the Origin of Species by Means of Natural
Evidence, Transformation Selection was published in 1859. I t changed forever our understanding
of the natural world. Dar win explained the mechanism that causes
Global context: Orientation in space organisms to change over time —the process that we call evolution.
and time His explanation shows how all forms of life could have evolved from
a universal common ancestor. A consequence of this is that humans
Statement of inquiry: share k inship with all other living organisms. This was a deeply
Evidence of past changes helps us shock ing idea to many people living in the 19th centur y, who had
understand life today and how it been taught that God created humans and that humans have a special
might be transformed in future. place in creation.
Dar win probably realised in 1838 that natural selection was the cause
of evolution, but he waited over
20 years before publishing this discover y. He has been accused of
fearing too much how religious leaders might react. The real reason
for such a long a delay is that Dar win was accumulating evidence. In
the Origin of Species, he presents a wealth of evidence for evolution by
natural selection. This is what all scientists, and indeed all non-scientists,
should do when tr ying to change our understanding. Dar win even
anticipated counter-arguments, by explaining how transformations
could occur to produce complex structures, such as the eye.
Since 1859 there have been many more discoveries that have changed
our understanding of the natural world. We now know that the universal
common ancestor lived far longer ago than Dar win imagined—perhaps
4 billion years ago. We know how environments on Earth can change
and how this can cause extinction of some species and oppor tunities
for others. We also know that humans are not only aected by
environments on Earth, but that we can profoundly change them.
For these reasons, it has never been more impor tant to study the life
sciences, and base our actions on an understanding of the impact that
we are having on planet Earth.
How were breeds of dog developed by humans?
The DNA of wild grey wolves ( Canis lupus) and dogs such as beagles
or bulldogs ( Canis familiaris ) is so similar that we can be condent that
all breeds of dog were developed from grey wolves. A process called
selective breeding or ar ticial selection was used to achieve this. This
diagram shows the basic process.
This statue at Shrewsbury
School of Charles Darwin
shows him as a young man.
He was a pupil at the school
between the ages of 9 and 16.
168
The characteristics of Dogs lack ing the desired
dogs are assessed to see traits are prevented from
which individuals have breeding, so their genes
the desired traits. are not passed on.
Ospring (puppies) Dogs with the desired
are reared until their traits are mated so they
characteristics can be pass on their genes to
assessed. ospring (puppies).
The changes in the traits of dogs may be ver y small with each new C
generation of dogs, but if the process of ar ticial selection is repeated B
over many generations, there can be massive changes—traits can A
be transformed. This is how dogs have become so dierent from
grey wolves and how so many breeds of dog with strik ingly dierent Evolution is gradual
appearance and behaviors have been developed.
change in traits of living
organisms that are
determined by genes.
I t is impor tant to remember three things about ar ticial selection: Traits are characteristics or
features of living organisms,
● Ar ticial selection can only change traits if they are due to the dogs’ that are determined
either by genes or by the
genes and not to the environment. environment.
● If something is changed during a dog’s lifetime, the ospring
of that dog will not inherit the changed trait—for example if a
dog’s tail is docked (cut shor ter) its ospring will not be born with
docked tails.
● Ar ticial selection can only work if there is variation in the genes.
If there is no genetic variation in a breed, then it is impossible
to select individuals with more desirable traits to breed the next
generation.
1. Dogs are often kept as pets, but most breeds were originally
developed to do something useful for their owners. Find out what
work these breeds originally did:
a) Alask an Husky c) Catahoula Cur
b) Bouvier des Flandres d) Doberman Pinscher.
169
E VOLUTION
2. What traits does a Dachshund have that make it ideally adapted to
help hunt animals such as badgers and rabbits?
3. What could a dog breeder do if they wanted to develop a par ticular
trait, but none of the dogs in their favourite breed had the genes
for that trait?
Dalmatian (25 kg) Papillon (2 kg)
Great Dane (55 kg) Nova Scotia Duck Tolling Retriever (33 kg)
Dog breeds show amazing variety in size, length of fur, color of fur and behavior. A grey wolf is shown on
page 131
C How are genes transformed by mutation?
B
A A gene is a sequence of bases in a DNA molecule. There are four
dierent bases in DNA, usually referred to by their initials A, C, G and T.
Mutations are They can be arranged in any sequence. Typical genes are at least a
thousand bases long.
changes to the base
Mutations are changes to genes. The smallest but most impor tant
sequence of a gene. type of mutation is when one base changes to another base, for
example C to G. This is called a base substitution. The change usually
A mutagen is a happens when DNA is being copied and a small mistake happens. I t
substance that causes an can also happen when high-energy radiation or cer tain substances
increase in the frequency (mutagens) cause chemical changes in DNA.
of mutations.
170
These are the most impor tant features of gene mutations:
● Mutations are random—any base in a gene can change, and it can
change to any of the other three bases.
● Mutations are heritable—although changes to base sequences in
sk in or other body cells are not passed on to ospring, mutations
in the ovar y and testis cells that develop into gametes can be
inherited.
● Mutations are rare—in the DNA that we inherit from each of our
parents there are about 3 billion bases but there will only be a few
base substitutions. Nearly all of our 25,000 or so genes are passed These “identical” twins
developed from one fertilized
on to our ospring unchanged. egg, but during their
development mutations will
● Mutations can change protein structure —most of our genes are have occurred in some genes,
so the twins are genetically
used to guide the production of a specic protein. A mutation in extremely similar but not
truly identical. A study of
such a gene may result in a change to the protein, which can aect the DNA from body cells of
two 100-year old identical
the structures and functions of an organism and thus its traits. twins found just eight base
differences out of 3 billion
● Mutations can be benecial, harmful or neutral—most mutations are
neutral because they do not occur in a critical part of a gene. Some
are harmful. A tiny minority of mutations are benecial.
One of the most famous mutations in human histor y happened near
the star t of a gene called HBB. This gene codes for one of the subunits
of hemoglobin, the protein in red blood cells that carries oxygen.
Here are the rst 21 bases in the gene:
GT G C A C CT G A CT C CT G A G G A G
1 10 20
The mutation changed the 17th base from A to T. This changes the The red blood cell on the left is
structure of hemoglobin only ver y slightly, but the change has major normal, but the one on the right
consequences. I t causes sick le -cell disease, which is a serious and has become sickle-shaped, due
lifelong condition. However, it also provides increased resistance to to a mutation in the hemoglobin
malaria. As a result, in par ts of the world where malaria is common, gene HBB
it can be an advantage to have a copy of the HBB gene with this
mutation. The mutation has therefore been passed on to ospring
and millions of people have inherited it.
The dierent versions of a gene produced by a mutation are called
A
alleles of the gene. The normal HBB allele is called Hb and the allele
S
with the sick le -cell mutation is called Hb . A few of the 25,000 or so
human genes only exist as one allele, but with most genes there are
two or more dierent alleles. In some cases, there are many dierent
alleles. This explains why no two humans have exactly the same genes,
apar t from identical twins.
171
E VOLUTION
How much variation is there in wild populations?
✓
We are ver y good at seeing the dierences between something that is at least par tly heritable, not
just due to the environment.
humans, but are usually slower to see variation in
Choose a reliable way of measuring or recording
other species. the trait in each individual. Collect this data from
as many individuals as you can.
●
Display the data using the most appropriate
● Visit a park, garden or wild area and take a look medium. A bar char t might be suitable, but not
at the organisms that are living there. Find a for some traits such as bird song.
species that is common, so you can quick ly ●
examine many individuals. Avoid organisms ● Present the results to your class, explaining
deliberately grown by humans such as crop how much variation you found in the trait you
plants or farm livestock. Do not cause any harm investigated.
to organisms or the environment.
● Find a trait that seems to be variable in the
species that you have chosen. I t should be
Snowdrops (Galanthus plicatus) ower in the spring. Gardeners have discovered many different varieties growing
in wild populations. A few of these are shown here
Water lilies and cacti
The white water-lily (Nymphaea odorata) grows in freshwater ponds and lakes, with its leaves oating on the
sur face and its roots in the mud below. The stems are shor t and fat. They grow horizontally over the sur face
of the mud.
1. What is the advantage of the following features in a leaf oating on the water sur face:
a) large air spaces
b) a coating of wax on the upper sur face, but not the lower sur face
c) pores (stomata) in the upper sur face, but not the lower sur face?
172
2. What is the advantage of these other features found in water lilies:
a) thin, exible leaf stalks that can
grow to any length
b) air canals in the leaf stalks, which are
connected to air spaces in the leaves
c) roots that grow downwards into
the mud?
Cac ti grow in dr y or drought-prone These water lilies, photographed from underwater, were
environments in Nor th and South America. growing in a lake near Cape Cod, Massachusetts. The
I n Africa there are plants that have vertical structures are leaf stalks (petioles)
ver y similar features but they are called
euphorbias, not cac ti. The most famous
t ype of cac tus is the saguaro (Carnegiea
gigantea).
3. What is the advantage of the following
features in the stem of a saguaro cactus:
a) many cells that can store water
b) folds in the sur face of the stem
(uting)
c) ver tical growth with few if any side
branches?
4. What is the advantage of these other
features in a saguaro cactus:
a) spines instead of leaves
b) pores (stomata) for absorbing
carbon dioxide that open at night
rather than in the day
c) roots that spread through the These saguaro cacti growing in the Sonoran desert are at
least a hundred years old
soil over a large area around the
stem?
5. What would happen if we planted a water lily in a deser t, or a saguaro cactus in a lake?
6. Choose some other examples of plants or animals that have features that adapt them to their
environment.
● You can choose any type of organism because all organisms need to be adapted to the conditions in
which they live.
● Find out what the adaptations are and how they help the organism to sur vive.
● The adaptations could be external appearance, internal structure, behavior or any other type of trait.
173
E VOLUTION
What is an adaptation?
In life sciences, the concept of adaptation is ver y impor tant. These are
the most impor tant features:
● Adaptations are features (or changes to features) that make an
organism better tted to its environment.
● Dierent adaptations are needed if an organism’s environment
changes.
● Only heritable traits are considered to be adaptations. For example,
having dark sk in is an adaptation to living in a ver y sunny climate,
but developing a sun-tan is not.
● Adaptations are not developed deliberately by living organisms—
they develop naturally and without planning. They are not
developed by design.
● We can never say that something is per fectly adapted—there is
always the possibility for fur ther improvements.
● Being better adapted gives an organism more chance of sur vival.
This is sometimes referred to as sur vival of the ttest.
A young herdsman in Nigeria Sk in color in humans is an example of adaptation. Sk in cells can
(latitude 9°N) with his cattle produce a black pigment called melanin. The amount of melanin is
at a watering place inuenced by several genes that we inherit from our parents. Melanin
stops ultra violet light (UV ) from penetrating the sk in. UV has two
eects on sk in cells:
● I t causes sunburn and, more seriously, it causes mutations in the
DNA of sk in cells, which may lead to sk in cancer.
● I t provides the energy needed for sk in cells to make Vitamin D.
Without sucient Vitamin D, the body can develop rickets.
Dark sk in is therefore an adaptation to living in an area with bright
sunlight containing lots of UV and there is more risk of developing sk in
cancer than rickets.
Light sk in is an adaptation to living in an area with weaker sunlight and
less UV, where rickets is more of a danger than sk in cancer.
Uyghur boy with his goats in Nearly all human populations that have been settled in an area for
Xinjiang Uyghur Autonomous more than just a few generations have sk in colors that are adapted
Region, China (latitude 42°N) to the intensity of UV light. There are a few populations whose sk in
colors do not match the amount of UV in the area where they live.
This is generally where a population has migrated nor th or south and
has not yet adapted to the change in UV intensity. This shows that it
takes thousands of years for a population’s sk in color to adapt to its
new environment—it does not happen by individuals becoming more
tanned or less tanned and passing this change on to ospring.
174
1. Discuss which of the boys in the photos is most at risk of
a) sk in cancer
b) rickets.
2. Humans now often migrate to a par t of the world where their sk in
color is not well adapted. Explain the health risks for these two
people and what they can do to avoid health issues:
a) someone with light sk in who moves from a nor thern area to
the equator
b) someone with dark sk in who moves from the equator to a
nor thern area.
What happens in the struggle for existence? An Icelandic boy with a black
and white lamb (latitude 65°N)
Organisms live in crowded communities. Even in a deser t, where
there seem to be large gaps bet ween the plants, roots are growing These are seedlings
ever ywhere in the soil. I n a forest, ever y suitable tree -hole is lik ely to of Himalayan balsam
contain a nesting bird during the breeding season. Predators that (Impatiens glandulifera)
are few in number in a communit y are probably each defending a that have germinated on
territor y and all available territories are occupied. a river bank in spring. This
plant grows rapidly to
The reason for this crowding is overproduction of ospring. Any about 2 meters in just a few
population that is thriving will tend to produce more ospring than months, then owers and
needed just to replace individuals that grow old and die. If ever y disperses its seeds. How
individual sur vives and grows to reproductive age, the numbers in a many seedlings are visible
population rise faster and faster. This is called an exponential increase. in the photo? There are only
enough resources for one
The resources available to the population don’t usually increase. For or two of these seedlings to
plants, there are limited amounts of light, water and minerals. For reach owering size. What
animals, there are limited amounts of food and space for breeding. will happen to the rest?
As a result, most organisms have to compete for resources. Sur vival is Which seedlings will be the
unlik ely for the individuals that get least resources. winners?
175
E VOLUTION
Competition is not the only hazard of living in a communit y. Most
organisms are in danger of being eaten by another organism. To
sur vive, an organism needs to prevent this from happening. Prey
must evade their predators and plants must deter the herbivores that
might eat them.
This green spiny organism is
a larva of the thistle tortoise
beetle (Cassida rubiginosa).
It is camouaged against the
spiny leaves of its food plant.
When its sensitive spines are
touched, the larva quickly
presses itself against the
leaf. The larva carries a lump
of feces on its back. What
are the advantages of these
behaviors?
The abiotic environment can also threaten sur vival— droughts, res,
oods and storms can all k ill, especially if an organism is not well-
adapted to sur vive such events.
A forest re in 2003 killed
some trees in Pusch Ridge
Wilderness, Arizona. In
2010, this was followed by
heavy snowfall and winter
storms, which felled many
trees. The survivors of these
natural disasters should have
plenty of resources available
to them to reproduce, and
therefore pass on their genes
Charles Dar win referred to the challenges of life as the “struggle for
existence”. In this struggle there are two rewards for winners—
they sur vive and they have a chance of reproducing.
176
Even at this stage though there are still challenges. In animals,L TA
reproduction depends on the success of mate selection. In plants, it
depends on getting gametes from one plant to another.
Who will the winners be? There is an element of chance, but sur vival
also depends on being well-adapted. The best-adapted individuals
tend to sur vive, nd a mate, reproduce and pass on their genes. The
less well-adapted usually fail to do these things. This dierence, based
on adaptation, is called natural selection
Affective skills
Analyzing and attributing causes of failure
During research projects there are often setbacks and failures. We have to
bounce back by nding the reasons for failure and overcoming them. If
we succeed, we are showing resilience.
An example of this happened during research into the evolution of the
peppered moth. A junior researcher was having no success at nding
specimens of this moth at night in a forest where it was known to live. He
was using a male moth to try to attract females. The researcher considered
many possible reasons for failure, but rejected them all. It was only when a
supervisor came with him that the real reason was found—the researcher
was applying midge-repellent to his face and hands before entering the
forest and this was repelling the moths along with the midges!
Have you ever experienced failures when you tried to do something?
Were you able to practice resilience, i.e. step back , analyze the reasons
for this failure and then nd ways of overcoming them?
Share your experiences with others in the class.
What features can natural selection change?
Natural selec tion can change any feature, as long as it is heritable . C
This includes features as small as the struc ture of an enz yme, up B
to patterns of behavior in animals. The photos on page 178 show A
recent cases where it is evident that natural selec tion causes change.
The environment changed in each case and natural selec tion then Natural selection
favoured dierent features, causing the population to adapt to the
new conditions. happens when the best
adapted individuals in
a species sur vive and
reproduce, passing on
genes to their ospring.
In each of these examples, the changes were relatively small and they Characteristics that can
happened over just a few years. With a longer time period, natural be passed from parents to
selection can cause more signicant changes, but only if these three ospring are heritable.
conditions are met:
● There is variation in the population. Variation is the range
of dierences between
members of a species.
● The variation is at least par tly heritable.
● Better-adapted individuals produce more ospring than others in
the population.
177
E VOLUTION
The peppered moth (Biston betularia) is easily On this plate there is a thin layer of gel mixed with
seen on this twig but is well camouaged on one strain of bacteria. Discs containing different
branches covered in lichens, especially birches. antibiotics have been placed on the gel. A clear area
During the 19th century, air in parts of Britain around a disc indicates that an antibiotic has killed
became very polluted, killing lichens and covering the bacteria. The bacteria must be resistant to one
trees in dark soot. Natural selection then favoured of the antibiotics because they have grown right up
a form of moth that had all-brown wings (melanic), to the disc. Within a few years of the introduction
rather than white wings with brown peppering. of an antibiotic to control a bacterial disease, the
Over a few decades populations in polluted areas percentage of bacteria that are resistant to it starts to
changed until the melanic form was dominant and increase.
the peppered form was very scarce. After pollution
control measures in the 1950s, the air became How does natural selection cause this?
cleaner and natural selection caused the peppered
form to become dominant again and the melanic
form to be suppressed.
How did natural selection, through the actions of
predators, cause these changes?
The medium ground nch (Geospiza fortis) has
been studied for many years on Daphne Major, one
of the smallest of the Galápagos Islands. It feeds
on seeds. After a severe drought in 1977, there
were fewer small soft seeds on which this nch
usually feeds, and more large hard seeds that
are produced by drought-tolerant plants. After
the drought, average beak size of the nches was
found to have increased.
How does natural selection cause beak size to
change?
178
The changes caused by natural selection are called evolution. I t may C
seem hard to believe that structures as complex as the human eye, or B
the ower of a wild orchid are the product of evolution, but scientists A
do not base their ideas on beliefs. They look instead for evidence. There
is power ful evidence for the evolution of life on Ear th and for natural Anatomy is the study
selection as the mechanism that causes it. In fact, it is reasonable to
assume that all life on Ear th is the product of natural selection, acting of the internal structure of
relentlessly, over vast periods of time.
living organisms.
Ver tebrae are the bones
that make up the spine.
What can we learn about evolution from anatomy?
Anatomists study the structure of living organisms. There are some
surprising similarities in the anatomy of organisms, for example in
the pattern of bones in ver tebrate limbs and in the development of
ver tebrate embr yos.
Ver tebrates with limbs are called tetrapods, which means having four
limbs. The main groups are amphibia, reptiles, birds and mammals.
Tetrapods use their limbs in many dierent ways, yet they all have
the same general pattern of bones. This similarity seemed odd when
Richard Owen (a 19thcentur y biologist) rst discovered it.
humerus
radius
ulna
wrist bones (carpals)
hand bones
(metacarpals
and phalanges)
human dog bird whale
1. Which tetrapods use their forelimbs in these ways: walk ing,
running, digging, climbing, gliding, ying, swimming?
2. Can you think of any other uses of tetrapod forelimbs?
3. Use the images to deduce the general pattern of limb bones in
tetrapods.
4. The photograph on the right shows the rst discover y of the long
hind leg of the dinosaur Diplodocus, by Henr y Fair eld Osborn in
1898. Did Diplodocus have the same general bone structure as
modern ver tebrate tetrapods?
5. What would have been surprising to Richard Owen about tetrapod
forelimbs all having the same general bone structure?
179
E VOLUTION When Dar win published the Origin of Species in 1859, he gave us a ver y
180 plausible explanation. All tetrapods are descended from one ancestral
species, so they have all inherited the pattern of limb bones of that
species. In some species the use of the limb changed and the bones
became adapted to a new use. Par ticular bones changed in size or
shape, or in some cases were lost, but the general pattern of bones
remained unchanged.
6. Discuss whether evolution by natural selection, or design oers a
more convincing explanation of similarities in the bone structure of
tetrapod limbs.
What can we learn about evolution from DNA?
I t is now relatively quick and easy to discover the base sequence
of a gene, or even of an organism’s entire genome. Ever-increasing
numbers of base sequences from many dierent species are available
to researchers in open access international databases. Base sequence
data provides ver y power ful evidence for evolution and helps to reveal
the evolutionar y histor y of groups of organisms. Here are some of the
key ndings from such research:
● Organisms that are in the same species have genes
with ver y similar base sequences.
● Organisms that are in dierent species have far more
dierences in their genes.
● The more closely related two individuals are, the
fewer dierences in the base sequence of
their DNA.
● Dierences in the base sequence of DNA
accumulate over time, so are used to estimate how
long it is since two species diverged from a common
ancestor.
● Computer analysis of base sequences can generate
“tree of life” diagrams which show the likeliest
evolutionar y histor y of a group of organisms.
● All organisms can be traced back to a universal
common ancestor, about 4 billion years ago.
This is a page from one of Charles Darwin’s notebooks,
dating from 1837. The tree diagram shows that he was
thinking that species can split by evolution to form
new species
Evolution of canids
Evidence from DNA was used to produce this tree diagram of canids (species
closely related to dogs). Divergence time in millions of years (Myr) is shown at
three points on the diagram.
Arctic fox
Kit fox
Corsac fox
Ruppells fox
Red fox
Cape fox
Blanfords fox
Fennec fox
910 34 Raccoon dog
Myr Myr Bat-eared fox
Shor t-eared dog
67.4 Crab-eating fox
Myr Sechuran fox
Culpeo fox
Pampas fox
Chilla
Dar wins fox
Hoar y fox
Maned wolf
Bush dog
Side -striped jackal
Black-backed jackal
Golden jackal
Dog
Grey wolf
Coyote
Ethiopian wolf
Dhole
African wild dog
Grey fox
Island fox
Black bear
Giant panda
Nor thern elephant seal
Walrus
Use the diagram to answer these questions.
1. To which species is the dog most closely related?
2. Is a maned wolf more closely related to a golden jack al or a bat- eared fox?
3. How long ago did a dhole and a chilla have a common ancestor?
4. How closely related are the three species of jack al?
181
E VOLUTION
What can we learn about evolution from embryos?
Fish, amphibians, reptiles, birds and mammals live in a wide range of
environments and their anatomy varies greatly when fully formed. We
might expect them to show dierent embr yonic development, but
instead there are strong similarities. All ver tebrate embr yos go through
the same early stages in their development. For example, a human
embr yo develops a tail, like all ver tebrate embr yos. I t also develops gill
slits which continue to develop in sh. Both of these features disappear
in later stages of human embr yonic development.
tail umbilical cord
developing gill slits
vertebrae
A human embryo four weeks
182 after fertilization
forelimb bud developing heart
Patterns of development in ver tebrate embr yos are controlled
by genes—they are heritable traits. The remark able similarities in
development are explained by all ver tebrates having genes inherited
from a shared ancestor. The dierences between ver tebrates are due to
evolution from that ancestor along dierent lines.
1. Can you explain features of human embr yos, such as the tail and
gill slits, in any way that does not involve evolution?
2. There are structures in a fully-formed human that do not seem to
have a purpose such as the appendix and the coccyx. What are the
reasons for them?
What can we learn about evolution from fossils?
Fossils are the traces in rocks of organisms that lived on Ear th in the
past. They tell us about the structure of these organisms. In the best-
preser ved fossils, it is even possible to see what the soft internal par ts
were like.
Fossils occur in sedimentar y rocks, which are laid down in a series of
layers (strata), one on top of another. Geologists have built up a ver y
accurate sequence of these rock strata, so they can place fossils in
chronological order according to the strata in which they are found.
This is called the fossil record.
Most recently, techniques have been developed to date rocks using
radioactive isotopes. I t is therefore possible to deduce when a fossilized
organism was living on Ear th. The time scale is in millions of years
before the present (BP). From these dates we can work out when
groups of organisms rst appeared on Ear th and, in the case of extinct
groups such as trilobites, when they disappeared.
The evidence from fossils to suppor t evolution can be summarized
using a series of general obser vations:
● Organisms that lived in the past were dierent from organisms alive
today, so there has been change.
● Sequences of fossils show progressive change over time, including
gradual transformations from one life form to another.
● There is an increase in the complexity and diversity of organisms
from the oldest to the youngest rocks that matches how we would
expect life to have evolved.
● Some major groups of organisms have disappeared permanently
from the fossil record.
1. What is the earliest evidence for these groups in the fossil record? Oviraptosaurs were ightless
dinosaurs but they had
a) euk ar yotes—organisms whose cells have a nucleus feathered wing-like
forelimbs and a feathered
b) ver tebrates—animals with back bones tail. The fossil seen here is
Caudipteryx zoui and was
c) ver tebrates with legs found in early Cretaceous
rocks at Liaoning in China.
d) hominids—the group of primates that only includes Imprints of the feathers
appear black. Recent
chimpanzees, gorillas, orangutan and humans modeling experiments show
that these feathers could
2. Are there any fossil-bearing rocks in the area where you live? What have generated lift and
increased running speed.
age are the rocks and what types of fossil have been found? They show that feathers and
wing-like forelimbs evolved
3. What evolutionar y changes were needed for: before true ight
a) sh to evolve into amphibians so that they could live on land; 183
b) reptiles with legs to evolve into snakes;
c) mammals living on land to evolve into whales living in water?
E VOLUTION 4. For one of the transformations in question 3, or another
184
transformation that interests you, nd out what the fossil record
tells us about how this change occurred.
What causes a species to become extinct?
Ever y species depends on its environment and is adapted to it. On
Ear th, there are often changes in the environment. For example, there
can be changes in sea level, temperature or amount of rainfall. There
can also be changes in which other species live in the community and
therefore in the predators, competitors or prey of a species.
When changes happen, there are several possible outcomes:
● Migration—move to a new location where the environment
matches the adaptations of the species.
● Evolution—become adapted to the new environment.
● Extinction—disappear because the population fails to sur vive and
reproduce.
A species that dies out in
an area is locally extinct. As
a result of local extinctions,
a species that was once
widespread may become
restricted to fewer and
fewer areas. If the last
population dies, that
species is extinct globally.
Many species of plants and
animals that once lived
on Ear th are no longer
found anywhere, and are
therefore extinct.
Megatherium americanum Fossil records tell us that
(giant ground sloth) of very large numbers of
Central and South America species have died out
had a body mass of up during ve brief periods in
to 4tonnes—extinction the Earth’s history. These
10,500years BP are called mass extinction
events. In each case there
was a major change to
environments on Earth. One
of the ve mass extinctions
was caused by an asteroid
impact, but the other four
were most likely due major changes in the volume of carbon dioxide or
oxygen in the Earth’s atmosphere.
We are currently living through the 6th mass extinction event. I t
star ted thousands of years ago, but has accelerated in recent decades.
Currently species are becoming extinct at a faster rate than ever before
in the histor y of our planet. What is the cause of this? What should we
be doing about it?
Pongo abelii (Sumatran
orangutan) from rainforests
on the island of Sumatra has
a body mass of up to 80 kg—
reduced to fewer than 7,000
individuals and now critically
endangered
185
E VOLUTION 1. Photos (i) to (iv) on this page show fossils of four animal groups that
(i)
(ii) are now entirely extinct:
(iii) ● Ammonites: a group of molluscs, related to octopus and squid
● Graptolites: a group of colonial animals related to acorn worms
● Non-avian dinosaurs: dinosaurs other than those that evolved
into birds
● Trilobites: a group of ar thropods, related to sea spiders and
horseshoe crabs.
a) Match the description of each animal group above to the
photos.
b) Find out when each of the four groups of animals became
extinct. Tr y to answer this question both in millions of years and
according to geological periods.
2. When did these species become extinct and what were the causes?
a) American mastodon ( Mammut americanum )
b) dodo (Raphus cucullatus)
c) Carolina parakeet (Conuropsis carolinensis )
3. a) There are plans to carr y out de - extinction of woolly mammoths
and some other recently extinct species. What is de - extinction
and how could it be done?
b) What are the arguments for and against de - extinction?
4. Of all the species that have ever lived on Ear th, are more species
extinct or more alive today?
5. a) How are humans causing the 6th mass extinction event?
b) What should we be doing to tr y to prevent it?
(iv)
186
Summative assessment
Statement of inquiry:
Evidence of past changes helps us understand life today and how it might
be transformed in future environments.
A B
C D Understanding evolution
1. What causes evolution? 6. Which are the ttest organisms in a
population, according to Dar win’s denition?
A. Mutation
A. Those that are largest
B. Natural selection
B. Those that are healthiest
C. Overproduction of ospring
C. The best look ing
D. People
D. The best adapted
2. When is evolution fastest?
A. When a species is tr ying to adapt.
7. What is required for natural selection to
B. When a species is in danger of extinction.
change a population?
C. When the ttest individuals sur vive.
I heritable variation
D. When the environment has changed.
II competition due to overproduction of
3. Which species are currently evolving?
ospring
A. No species
III dierences in reproductive success
B. Only humans
between individuals
C. All species apar t from humans
A. I and II only
D. All species
B. II and III only
4. What is the best description of evolution?
C. I and III only
A. Evolution happens by chance.
D. I, II and III
B. Evolution happens because organisms
are tr ying to improve themselves.
8. Which traits of an organism are adaptations?
C. Evolution happens in small steps that
A. Traits that have changed during the
lead towards fully-formed organisms.
lifetime of the organism.
D. Evolution makes organisms better
B. All the heritable traits of an organism.
adapted.
C. Heritable traits that make an organism
5. What is the quickest that evolution can suited to its environment.
happen?
D. Traits that can be changed by the
A. During a single lifespan environment.
B. Between one generation and the next
C. Over a few hundred years
D. Over millions of years
187
E VOLUTION
Questions 9–10 refer to this evolutionar y tree.
I II III IV
9. What does the red node represent? 10. What conclusion can be drawn?
A. The time when I split from the other groups. A. I is more closely related to II than to III and IV.
B. The stage when II split from the other groups. B. II is more closely related to III than to IV.
C. The shared ancestor of II, III and IV. C. III is as closely related to I as to II.
D. The time when half the evolution has D. IV is more closely related to II than to I.
happened.
A B
C D Spaghetti worms
11. Model worms can be made by cook ing spaghetti with food dye
added to the water and then cutting the cooked spaghetti into 50mm
lengths. Single food dyes can be used to get pure colors such as green.
Alternatively, dyes can be mixed, for example, mix red and black to
make brown.
If placed on a bird table or other bird-only feeding area, local species of
bird should feed on the spaghetti worms. If there are no birds to feed
on the worms, you could use students to search for them in an area
where you have distributed them.
a) Design a simulation of natural selection using spaghetti worms.
Explain these aspects of your design:
● the numbers and colors of spaghetti worm you will use as a rst
generation
● where you will put the rst generation of spaghetti worms and
what the environment around them will be, including its color
● how you will ensure that your simulation is a fair test
● how you will assess the feeding of birds on the rst generation of
spaghetti worms
● how you will simulate reproduction of the worms that are not
eaten and the inheritance of color by the next generation
● the number of generations of spaghetti worms you will include in
your simulation. [8]
b) Formulate a hypothesis—a prediction of what you expect to nd
when you carr y out your simulation. [2]
188
C D Tawny owls
Tawny owls (Strix aluco) in Finland have either
grey or brown plumage. This is a heritable
trait that does not change during an owl’s
lifetime. Large numbers of tawny owls have
been captured, marked and released and their
sur vival and reproduction has been monitored
since the 1960s. The graphs show the change
in the frequency of the brown tawny owl in the
population and sur vival rates according to the
depth of snow in winter.
12. a) What is the propor tion of brown tawny
owls at the star t and end of the study
period? [2]
A tawny owl swoops to catch a mouse
b) Calculate the propor tion of grey tawny
owls at the star t and end of the study
0.5 1
period. [2] etar lavivrus
slwo nworb fo noit roporp
13. a) What does the right-hand graph tell 0.4 0.8
us about snow depth and sur vival of
0.3 0.6
grey and brown tawny owls? [2]
0.2 0.4
b) Suggest an explanation for the
dierences in sur vival between
0.1 0.2
the two forms of tawny owl. [2]
c) Suggest an explanation for the change 0 0
1960 1970 1980 1990 2000 2010 0
year 5 10 15 20 25
in the propor tions of grey and brown snow depth (cm)
tawny owls during the study period. grey owls
brown owls
Source of data: Climate change drives microevolution in a wild bird,
Patrik K arell, K ari Ahola, Teuvo K arstinen, Jari Valk ama & Jon E.
Brommer, Nature Communications , 2011, 2, 208
A B
C D Responses to global warming
There is abundant scientic evidence showing that cer tain human activities
cause global warming and other aspects of climate change. Despite this,
some people still argue that there is no need for us to change our activities.
For example, in 2018 Australian environment minister Melissa Price stated
that it would be “irresponsible” to commit to phasing out coal burning.
One argument that some have put for ward is that, in the event of a change
caused by global warming, all species in natural ecosystems will be able to
evolve the traits needed to sur vive.
14. Use scientic k nowledge and understanding to explain:
a) how natural selection could make a species adapt to warmer
temperatures [4]
b) reasons for doubting whether all species will successfully
adapt if temperatures on Earth continue to rise rapidly [3]
c) reasons for concern that changes to the Ear th’s atmosphere
could lead to a mass extinction event. [3].
189
Index
Index headings in bold indicate key terms; page numbers in italics indicate illustrations/caption text.
abdomen 99 bacteria 62, 137, 146, 152, 155, 178 Brown, Rober t 32, 33
Bak htiari tribe 122 brucellosis 139
abiotic components 148, 159 banana cells 27 butter ies 70, 120
Bangladesh 122
adaptation 38, 174–5 bar-tailed godwits 116, 117 C-ferns 75
barrel sponges 80 caciques 138
adipose tissue 57, 96 bases, DNA 9, 10, 170, 180–1 cacti 173
beavers 133, 137 Calder, Alexander 128
adzuk i bean weevils 143 bees 80, 82 cancer 23, 37, 174, 175
beetles 71, 176 canids, evolution of 181
aerobic respiration 56 binar y code 9 capillaries 97
biodiversity 130, 143 carbohydrates 50
agoutis 63 bioluminescent cells 43 carbon cycle 157–9
biometric data 3 carbon dioxide 154, 157, 158, 160–5
air 151 biotic components 148, 159 carbon sinks 160
birds carrots, structure of 30–1
see also atmosphere car tilage 115
body heat conser vation 94, 130 catalysts 52, 53
algae 43, 62, 95, 137, 150 “breast meat ” 115 cattle 74
communities 130 Caudipteryx zoui 183
alleles 17–18, 171 eggs 49, 83 cell membrane 26, 32, 33, 34, 36,
ight mechanism 114–15
Alpine salamanders 67 ocks 146 42–3, 45
migration 110, 112–17, 125–7 cell wall 32, 33, 34, 36, 45
alveoli 97 mutualism 137 cells 24–45
natural selection 178
amino acids 12, 50, 155 reproduction 66, 69, 72, 79, 88–9 animal cells 36
social groups 138 components of 32, 35–7
ammonites 186 territoriality 135, 136 discover y of 28–9
Wytham Woods research 136 division of 14, 84
amoebas 39 bison 132, 133, 137, 141 drawings of 34–5
black poll warblers 117 electron microscopy 45
amylase 53 Blaine, David 46 energy exchange 43
blood cells 42, 45, 171 uorescent cells 43
anaerobic respiration 56 blood groups 16, 17, 18, 106 functions of 96
blue tits 136 gas exchange 42
anatomy 179–80 blue whales 92 models of 26
Blue Zones 139 multicellular organisms 94
ancestr y, DNA analysis 7 body heat conser vation, birds 94, 130 nucleus 13, 32, 33, 34, 35, 36, 39, 45
bonobos 71 organism types 31
anemia 45 brain, sensor y inputs 101–3 phosphorescent cells 43
Brazil nuts 63, 64–5 plant cells 32, 35, 36, 37, 45, 60, 61
animals brown adipose tissue 57 respiration 56–7
structure of 32, 35–7
cells 36
climate change 118–19
competition 134
fer tilization 79–80, 83–4
antagonistic pairs 114
antibiotics 178
antibodies 139, 141
ants 137, 138
aphids 87
apple seeds 83
aquariums, mak ing 150
aquatic ecosystems 149–50, 151, 156
Arctic terns 116
ar t 128–9, 166
ar ticial selection 168–70
asexual reproduction 68, 86–7
aspen trees 131, 132, 133
atmosphere, CO concentrations
2
160–5
A zura (cruise ship) 124
190
types of 96 crime scene investigation 7, 8 eccentricity 109
unicellular organisms 38–9, 94 CRISPR/Cas9 system 20 ecosystems 146–65
cellulose 137 cruises 124
centi 10 cuticle 61 aquariums, mak ing 150
cerebellum 102, 103 cyanobacteria 62 aquatic ecosystems 149–50,
cerebral cor tex 103 cystic brosis 17
cerebral hemispheres 102, 103 cytoplasm 36, 38, 39, 45 151, 156
cerebrum 102, 103 and climate 152–3
cer vix 32, 76 dandelions 111 decomposers 154, 155
chimpanzees 138, 140 Dar win, Charles 69, 168, 176, 180 as open systems 148, 151
China data storage, DNA 9, 10–12 organism types 154
fer tility rate 89 decomposers 154, 155, 158, 159 terrestrial ecosystems 151–3, 163
migration 124 deer 72 egestion 52
Uyghur people 174 deoxyribonucleic acid see DNA eggs
chloroplasts 33, 34, 35, 36, 38, 45, ‘designer babies’ 20 birds and reptiles 49, 83
60, 61 diet, humans 50–1, 55, 57 gametes 73, 74, 76, 77, 78, 80, 81,
chromosomes 4, 13, 14–15, 84–5, 86 diusion 40–1
cilia 39 digestion 49, 52–4 83, 84, 85
ciliates 39 dinosaurs 179, 183, 186 ejaculation 79
circulator y system 101 Diplodocus 179 electron microscopes 45, 102
citizen science 17, 60 diseases, causes of 139 elk 131, 132–3, 137
climate embr yos 84, 85, 96, 182
and ecosystems 152–3 see also brucellosis; cancer; Ebola; endocrine system 101
global warming 110, 118–19, 162, pathogens; rickets; scur vy ; energy
sick le -cell disease
163, 189 bird migration 116
clothing 167 distribution maps 118 cells 43
Cloud Gate, Chicago 3 DNA (deoxyribonucleic acid) 4–12 respiration 57
coal 160 environment 18
cod 149 base sequences 10, 180–1 enzymes 12, 53, 83, 155
codons 8, 9 bases 9, 10, 170, 180–1 epidermis 32, 33, 61, 97
collagen 50, 57 copying of 11 epididymis 76, 77
Colombia 129 evolution 180–1 epithelium 96, 97
communities 128–45 gene editing 20 estimates and guesses 27
information storage 9, 10–12 estrogen 78, 79, 85
competition 134–5 models of 5, 10 ethnicity, and organ donation 107
denition 130 molecule size 10 evolution 166–89
food chains 131–3 mutations 170–1 adaptation 174–5
mutualism 137 samples of 6, 7 anatomy 179–80
predators, parasites and structure of 4–5 ar ticial selection 168–70
uses of 6–8 of canids 181
pathogens 139–43 DNA ngerprinting 6, 8 denition 169
social groups 138 dogs, selective breeding 168–70 DNA 180–1
competition 134–5, 175 Donne, John 128 embr yos 182
comunas (slums) 129 drainage 151 extinction 184–6
cones 81 drawing, cells 34–5 fossils 183–4, 186
conict 122 dredging 145 mutations 170–1
conifers 81, 176 drought 163 natural selection 177–9
connective tissue 115 dynamic equilibrium 130 struggle for existence 175–7
conser vation groups 134 experiments
consumers 131, 132, 154, 158, 159 ear wax 16, 17 bird wing dissection 115
controversial issues 20 Ear th’s orbit/tilt 109 carrot structure 30–1
coral 79, 149 Ear thships 24 diusion 40–1
cork cells 29 Ear thwatch Institute 163 FACE experiments 164–5
corn 48 ear thworms 152 plant competition 135
cranes (birds) 117 Ebola 140 plant growth, light eect on 19
seed dispersal 111
191
INDE X
senses, investigating 104 release of 76–9 humans
starch digestion 53–4 sexual/asexual reproduction 86 body systems 100
tea bag decomposition 156–7 sperm 73, 74, 77, 78, 79, 80, 83, 84, 85 diet 50–1, 55, 57
extinction 7, 184–6 Gamme, Aleksander 58–9 embr yonic development 182
gannets 135 fer tility 89
FACE (Free -Air Carbon dioxide gas (carbon sink) 160 fer tilization 84
Enrichment) experiments 164–5 gas exchange 42, 61, 97 migration 120–4
gender 85–6 organs 99–107
fashion 167 gene editing 20 population 49, 69, 89, 121, 130
fats 50, 65 genes 2–23 sk in color 174–5
alleles 17–18 social connections 139
see also adipose tissue base sequences 10, 180–1
feathers 183 chromosomes 14–15 hurricanes 108
ferns 37, 74, 75, 80, 87, 108, 160 copies of 14–15 hybridization 70
fer tility rates 89–91 denition 12 Hydrangea 19
fer tilization 79–81, 83–4 ‘designer babies’ 20 hypotheses 40, 41, 112, 113, 135
fetuses 4, 84 DNA 4–12
lms 167 inheritance 18–19, 68 Iceland 109, 175
nches 178 location of 14–15 ID cards 3
sh 66, 118–19, 150 mutations 170–1 identity 2, 3, 4, 18–19
sheries 144–5, 149 storage of 13 immunity 139, 141
agellates 38 genetic code 8, 9 information storage, DNA 9, 10–12
eas 140 genetic diseases 20, 21 ingestion 52
ight, birds 114–15 genetic ngerprinting 6, 8 inheritance 18–19, 68, 70
ocks, birds 146 genus 69 integumentar y system 101
Flower Clouds (Redon) 166 germination 110, 111 invasive species 134
owers 81, 87 GH (growth hormone) 12, 14 Iran 122
uorescent cells 43 giant ground sloths 184
food 46–65 giga 10 journals 127
glaciers 109
Brazil nuts 63–5 global warming (climate change) K apoor, Anish 3
deciency diseases 50 110, 118–19, 162, 163, 189 k idney transplants 105–7
diet 50–1, 55, 57 glucose 48, 53, 56, 59 kilo 10
digestion 52–4 gonads 75, 76, 85 k iwis 66
nutrients 50–1, 64 Gormley, Antony 128
photosynthesis 59–61, 62 graptolites 186 lactic acid 56
respiration 56–7 great tits 136 ladybirds 87
sustainable production of 65 group work 101 leafcutter ants 138
food chains 131–3 growth hormone (GH) 12, 14 leaves 36, 37, 60, 61–2
food webs 132 guesses and estimates 27 Lee, Harper 167
forensics 7, 8 gut 52 Leeuwenhoek, Antonie van 28
forests 163, 176 lemmings 112
fossil fuels 160, 161 hard drives 10 lichens 95, 137, 178
fossils 108, 183–4, 186 hemoglobin 50, 171 lift 114
Free -Air Carbon dioxide Enrichment hens’ eggs 49 ligaments 115
(FACE) experiments 164–5 heritable characteristics 177 lilies 47, 74
Froome, Chris 55 hibernation 112, 113 Linear B script 9
fruits 51, 83, 111 Himalayan balsam 175 lipids 50
fulmars 88–9 Hooke, Rober t 28–9 liver wor t 37
fungi 137, 138, 152, 155 hornbills 72 lobsters 119
hornwor t 32 Lyme Bay, Dorset 145
gametes hosts 139, 141, 142 lymph 101
eggs 73, 74, 76, 77, 78, 80, 81, 83, housing 24–5, 90–1 lymphatic system 101
84, 85 lynx 141
fer tilization 79–81
production of 75–6, 78, 84–5
192
mammoths 185 neonicotinoids 82 plants
Maori 123 ner ve bers 103 cells 32, 35, 36, 37, 45, 60, 61
mass extinctions 184–5 ner vous system 101–3 competition 135
mating 71–3, 78, 79 neurons 102, 103 ecosystems 150, 152
Mauna Loa, Hawaii 158, 161 New Zealand 123, 144–5 fer tilization 80–1
medium ground nches 178 Newfoundland 142 growth of 19
mega 10 Nigeria 174 migration 118–19
meiosis 84–5, 86 Nor th America, ecosystems 152–3 photosynthesis 48, 49, 59–61, 62,
melanin 174 novels 166, 167 131, 150, 157, 159
melting points 65 nucleus, cells 13, 32, 33, 34, 35, 36, “plant food” 60
membrane, cell 26, 32, 33, 34, 36, reproduction 177
39, 45 roots and stems 97–8
42–3, 45 nutrients 50–1, 64 seed dispersal 110, 111
meninges 102 nuts, Brazil 63, 64–5
menopause 78 podocytes 96
menstrual cycle 77 oak tree growth 164–5 polar bears 162
menstrual hygiene products 79 ocean sunsh 66 pollen 80, 81, 82
menstruation 76, 77 octopuses 11 pollination 81, 82, 137
micro 10 oil 160 population
micrometers 32 On the Origin of Species (Dar win)
microscopes 26, 28, 29, 32, 33, 45, 102 exponential increase 175
migration 108–27 168, 180 humans 49, 69, 89, 121, 130
open systems, ecosystems as 148, 151 precession 109
birds 110, 112–17, 125–7 orangutans 185 predators 137, 138, 139–43, 176
and climate change 118–19 orchids 71 prexes 10
humans 120–4 organ donation 104–7 prey 135, 137, 141, 176
milli 10 organisms 92–107 producers 131, 132, 154, 159
millimeters 32 progesterone 84, 85
minerals 50, 59, 60, 151 denition 94–5 proteins 12, 13, 50, 57
Minoan civilization 9 ecosystems 154 prothalli 74, 75
mitochondria 35, 36, 39, 45 ner vous system 101–3 pseudopodia 39
moa 7 organs 52, 99–107 puber ty 78, 85
mobiles (k inetic ar t) 128 tissue 96–7
molds 31 organs 52, 99–107 rabbits 141
molecules 92 ovaries 75, 76 rattlesnakes 118
monarch butter ies 120 oviraptosaurs 183 receptors 101
moose 142 ovulation 77, 78 red blood cells 42, 45, 171
Morse code 9 Owen, Richard 179 Redon, Odilon 166
mosquitoes 15, 84 owls 189 redstar ts 125–7
mosses 36, 60, 80 oxygen 154 Rembrandt 2
moths, peppered 178 reproduction 66–91
movies 167 parasites 137, 138, 139–43
MRI scans 102 Parker Solar Probe 147 asexual reproduction 68, 86–7
multicellular organisms 94 par ticles 40, 41 fer tilization 79–81, 83–4
Murasak i Shik ibu 166 paternity test 6 male/female dierences 73–4
mutagens 170 pathogens 40, 139–43 mating 71–3, 78, 79
mutations 21, 22, 170–1 peacocks 72 par tner selection 71–3
mutualism 137 penguins 69, 130 redstar ts 126–7
Myanmar 122 penis 76 sex determination 85–6
myoglobin 115 peppered moths 178 sexual reproduction 15, 68,
pesticides 82
nano 10 phloem 97, 98 86–7
natural disasters 176 phosphorescent cells 43 species 69–71
natural selection 177–9 photosynthesis 48, 49, 59–61, 62, research
navel 16 collaboration 101
131, 150, 157, 159 failure analysis 177
plankton 62, 150, 160 website evaluation 58
193