LECTURE NOTE WEEK 2_SEM2

CHAPTER 2

2.2 ENERGY FLOW THROUGH ECOSYSTEM

LEARNING OUTCOME:
State the type of ecological pyramids in
relation to trophic level.

TROPHIC LEVEL

• Position / stage that an organism occupies in a food chain
• Usually four or five trophic levels

Primary

Trophic level 5
Trophic level 4

Trophic level 3
Trophic level 2
Trophic level 1

ECOLOGICAL PYRAMID

• A graphical representation of the relative energy

value, number of organisms and biomass at each
trophic level.

• 3 types of ecological pyramids :-

i. Pyramid of numbers
ii. Pyramid of biomass
iii. Pyramid of energy

ECOLOGICAL PYRAMID

➢ Shows the number of individual Example
organisms for each trophic level in a 1: clover → snail → thrush → hawk
food chain of an ecosystem

➢ In most pyramids of numbers, fewer
organisms occupy each successive
trophic level.

➢ Number of producers (at the
pyramid base) are larger.

➢ At the top, organisms are larged-
sized and the number is smaller.

➢ Can be upright, inverted or a partly
inverted

➢Inverted pyramid of number:

•Higher trophic level have more organisms than lower trophic
level (often observed among decomposer, parasite and
herbivorous insects).

Example 2: Oak tree → Insects → Woodpecker Example 3: Grass → Rabbit → Flea

Secondary consumer
Primary consumer
Producer

Secondary consumer
Primary consumer
Producer

ECOLOGICAL PYRAMID

➢ Indicates the total biomass of all organisms in each trophic level

➢ *Biomass may be represented as total volume, dry mass or wet
mass.

➢ Most biomass pyramids narrow sharply from primary producers at
the base to the carnivores at the top

➢ Can be upright, inverted or a
partly inverted

Unit : mass / unit
area
(e.g. 1.5 g / m2)

ECOLOGICAL PYRAMID

➢ An inverted biomass pyramid.
➢ Example: When biomass of phytoplankton < biomass of

zooplanktons as the phytoplankton are smaller in size &
rapidly consumed (reproduce rapidly but rapidly
consumed)

An inverted
biomass pyramid

ECOLOGICAL PYRAMID

➢ Shows energy content of all organisms in each trophic level.
➢ Has large bases and get progressively smaller through

succeeding trophic level----- >to show energy lost.
➢ Can NEVER be inverted

Unit : energy / unit area / year
e.g. : 6 kJ m-2 yr-1

Less trophic levels, less energy loss

2.3 BIOGEOCHEMICAL CYCLE

LEARNING OUTCOMES:

State biogeochemical cycle components (cycling
pool and reservoir pool) .

State example of biogeochemical cycle (nitrogens
cycle, phosphorus cycle,carbon cycle and sulphur
cycle)...

2.3 BIOGEOCHEMICAL CYCLE

 Biogeochemical cycles are cycling of matter from
the living organisms (biotic components) to the
nonliving, physical environment (abiotic
components) and back again.

Matters flow through the ecosystem from one
organism to another. Flow of chemical element in an

ecosystem are constant

• Cycling pool
- involve biotic components
- the portion of environment where organism
takes their nutrient
- chemical element are smaller quantity
(move actively)

• Reservoir pool
- involve abiotic components
- portion/region of Earth
(atmosphere, hydrosphere, lithosphere) act as
storehouse for chemical elements
- chemical element are larger quantity (does not move
actively)

EXAMPLE OF BIOGEOCHEMICAL CYCLE

Carbon cycle Nitrogen cycle

EXAMPLE OF BIOGEOCHEMICAL CYCLE

Phosphorus cycle Sulphur cycle



Sedimentary rock on the bottom of sea floor may lift to form land surfaces



5.
3.

4. 2.

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1/01/2023



2.4 CONSERVATION & MANAGEMENT

LEARNING OUTCOME:
Describe sustainable development.
Describe conservation of diversity in
Malaysia.

Sustainable
Development

• "Development that

meets the needs of the
present without
compromising the ability
of future generations to
meet their own needs.“
from the World
Commission on
Environment and
Development’s

Conservation • The maintenance of species and

of diversity ecosystems is a keystone to sustainable
in Malaysia development.

• Conservation is usually carried out in two

ways; In-situ and Ex-situ conservation.

• In-situ conservation is a method involving

the management and monitoring of
biodiversity in the same area where it is
encountered.

• Example: National parks, biosphere

reserves, parks, sanctuaries.

Conservation • Ex-situ conservation

of diversity • The preservation of components of
in Malaysia
biological diversity outside their natural
habitats.

• Example: Botanical garden, Zoo

2.5 POPULATION GROWTH

LEARNING OUTCOME:

Describe natality and mortality and their
effects on the rate of population growth.

Natality Natality:
(Birth Rate)
• The number of offspring produced in a
vs
given time period.
Mortality Mortality:
(Death Rate)
• The number of individuals died in a

given time period.

• If natality > mortality, population size

increases;

• If mortality > natality, population size

decreases

• If natality = mortality, population is

stable (net growth/ growth rate is
zero)

Basic forms Exponential Growth Curve
of growth (J-shaped growth curve)
curves can
be identified Logistic Growth Curve
(Sigmoidal Growth Curve).

Logistic Growth Curve Exponential Growth Curve

* both graph cannot start with 0

Limiting Factors Affecting
The Population Size

• Density Dependent Factors
• Density Independent Factors

Density • Factors which regulate population
Dependent
Factors growth only when population size
is high.

• Leading both to decreased

natality and increase of mortality

Example:

• Interspecific and Intraspecific

Competition (for resources/food)

• Territorial behaviour
• Niche (Predation/prey-predator

interaction, habitat)

• Overcrowding/limited space

,parasitism, Infectious diseases

Density • Factors which tend to
Independent
Factors effect population growth
irrespective of population
size.

• The rate of a population at

any instant is limited by
something other than the
size of the population

• Ex: storm, fires, drought

and other natural
occurrences.

• A typical abiotic conditions,

ie: changes in climate/
weather , natural disasters
(e.g. flood, forest fire,
tsunami) , pesticides by man
in agriculture