CHAPTER 2: ECOLOGY...CHAPTER 2: ECOLOGY SUBTOPIC : 2.1 Ecosystem Concept LEARNING OUTCOMES : a. Define ecosystem. b. Describe lake ecosystem based on: i. light penetration (photic

Biology Student’s Companion Resources SB025

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CHAPTER 2: ECOLOGY

SUBTOPIC : 2.1 Ecosystem Concept

LEARNING OUTCOMES : a. Define ecosystem.

b. Describe lake ecosystem based on:

i. light penetration (photic and aphotic)

ii. distance from shore and water depth (littoral, limnetic)

c. Describe terrestrial ecosystem of tropical rainforest stratification

(emergent, canopy, understory, ground/forest floor).

MAIN IDEAS

/KEY POINT EXPLANATION NOTES

a. Define

ecosystem

Ecosystem:

A basic functional unit of nature including both organisms and

their non-living environment.

Each interacting and influencing each other and necessary for

maintenance and development of the system.

Odum (1969)

b. Describe lake

ecosystem based

on:

i. light

penetration

(photic and

aphotic)

Zonation of lake ecosystem is based on:

1. Light penetration.

a. Photic

• Upper part of lake or marine environment. • Light is sufficient for photosynthesis. • Biotic components: almost all are the primary producer (high

productivity occurs).

b. Aphotic/Profundal

• The deep open water. • Region that do not received light.


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ii. distance from

shore and water

depth (littoral,

limnetic)

• No photosynthesis. • Biotic components: some fish, decomposer, detritivore

Compensation point:

Point in between photic and aphotic zone where the rate of

photosynthesis equal to the rate of respiration.

2. Distance from shore and depth of water:

a. Littoral

• Area near the shore that receives sunlight.

• Extending down to the depth where rooted plants stop growing.

• Most photosynthesis occurs in this part of the lake.

• Diversity greatest here.

Animals Plants

• Suspension feeders (clams)

• Herbivorous grazers (snails)

• Herbivorous and carnivorous insects

• Crustaceans

• Fishes

• Amphibians

• Some reptiles

• Mammals

• Emergent plants

• Floating plants

• Submerged plant

b. Limnetic

• Open surface water, away from the shore.

Compensation Point


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• It is above the aphotic/profundal zone. • The main photosynthetic body of the lake. • This zone produces the oxygen and food that support the lake's

consumers

• Occupied by a variety of phytoplankton, consisting of algae and cyanobacteria, as well as zooplankton,

small crustaceans, and fish.

c. Describe

terrestrial

ecosystem of

tropical rainforest

stratification.

1. More complex than aquatic ecosystem.

2. Competition for light is intense.

3. Stratified, includes:

• Emergent - Trees that project 50m – 60m above the general level of the

canopy.

• Canopy - Contains many kinds of epiphytic plants. - Forms a continuous evergreen carpet - Plants are about 25 – 35 m tall.

• Understory - Many understory species are vines that attach themselves to the

tall tree as they grow towards the sun.

- Dark and humid area contains saplings between the trunks of larger trees.

- About 15 – 24 m high.

• Shrub - Contains small trees and shrubs.

• Ground layer / forest floor - Composed of tall herbs and ferns with a deep litter of fallen

leaves and branches.

http://en.wikipedia.org/wiki/Profundal_zonehttp://en.wikipedia.org/wiki/Profundal_zonehttp://en.wikipedia.org/wiki/Phytoplanktonhttp://en.wikipedia.org/wiki/Algaehttp://en.wikipedia.org/wiki/Cyanobacteriahttp://en.wikipedia.org/wiki/Zooplanktonhttp://en.wikipedia.org/wiki/Crustaceans


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SUBTOPIC : 2.2 Energy Flow through ecosystem

LEARNING OUTCOMES : a. Explain the energy transfer in ecological pyramids in

relation to trophic level.

b. Calculate energy loss in each trophic level.


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MAIN IDEAS


a. Explain the

energy transfer

in ecological

pyramids in

relation to

trophic level.

1. Trophic level

The position that an organism occupies in a food chain.

2. Ecological pyramid

A diagram representation of the relative energy value at each

trophic level / the flow of energy through the food chain


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MAIN IDEAS


3. Types of ecological pyramids:

a. Pyramid of numbers

- Based on counting numbers of organisms at each trophic

level.

b. Pyramid of biomass

- Which note weight (usually dry weight) of organisms at

each trophic level.

c. Pyramid of energy

- Which monitor energy content of organisms at each

trophic level.

Advantages Disadvantages

Easy to count Ignores size of organism

No organisms

killed

Numbers can be too great to represent

accurately

Numbers will change as the organism are

born or being killed


Shape always

gets narrower

nearer the top

Impossible to catch/weight all organisms

Organisms need to be killed in order to

measure its dry mass.


Shows efficiency

of energy

transfer from one

trophic level to

another

Very difficult and complex to collect

energy data

b. Calculate

energy loss in

each trophic

level.

1. Only 10% of energy is transferred from one trophic level to

another. The rest is lost as heat in:

• Respiration

• Excretion

• Photosynthesis

• Movements

• Growth


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MAIN IDEAS


SUBTOPIC : 2.3 Biogeochemical Cycles

LEARNING OUTCOMES : a. Describe biogeochemical cycle components (cycling

pool and reservoir pool) in carbon and nitrogen cycles.

b. Illustrate phosphorus cycle.

MAIN IDEAS


a. Describe

biogeochemical

cycle

components

(cycling pool

and reservoir

pool) in carbon

and nitrogen

cycles

1. Biogeochemical Cycles

• A pathway by which a chemical substance moves through biotic and abiotic compartments of Earth.

• Each cycle summaries the movement of chemical elements through the living components of ecosystem

2. Components of biogeochemical cycles:

Reservoir Pool (sinks) Cycling/Exchange Pool

Portion of the earth that acts as

a storehouse for the element.

Portion of the environment from

which the plants & animals take

the abiotic component from

reservoir.


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A. Carbon Cycle

Reservoirs Pool:

• Atmosphere : As gas CO2

• Ocean : As dissolved CO2 in the form of carbonate ion (CO32-) and bicarbonate ion (HCO3-)

1. The global movement of carbon between the abiotic

environment including the atmosphere and the organisms is

known as the carbon cycle.

2. Carbon must be available to organism because proteins,

nucleic acids, lipids, carbohydrates, and other molecules

essential to life contain carbon.

3. The process:

• Carbon dioxide from the air combines with water by

diffusion to produce bicarbonate ion (HCO3-).

• This is the main source of carbon for algae.

• Similarly, when aquatic organisms respire, the CO2 they

give off becomes HCO3-.

• Terrestrial plants fix CO2 directly from the atmosphere for

photosynthesis.

• The sugar formed are then assimilated into complex

carbohydrates, fats, proteins and nucleic acids.

• The carbon in this form passes from producers to

consumers in the form of food and finally to decomposers.

• When the plants and animals died, saprophytic organisms

will be decomposing the organisms and make it available

again to living organisms.

• CO2 is returned to the atmosphere through respiration of all

living organisms.


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• Combustion also return CO2 to the atmosphere.

• Erosion of limestone dissolved CO2 to the water and

atmosphere, making it available to reproduce again.

B. Nitrogen Cycle


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Reservoir: Atmosphere

1. Nitrogen is an essential part of proteins, nucleic acids and

chlorophyll.

2. Nitrogen is very stable and does not readily combine with other

elements.

3. Must be broken up by chemical reactions.

4. Involves 5 process:

a. Nitrogen fixation

N2 enters ecosystems through 3 pathways:

- Atmospheric N2 fixation

• Usable N2 is added to the soil by combustion,

volcanic action, lightning discharges

- Biological N2 fixation

• Certain prokaryotes convert N2 to minerals that can

be used to synthesize nitrogenous organic

compounds

• Mutualistic blue-green bacteria : Rhizobium

• Free-living blue-green bacteria : Azotobacter,

Clostridium

• Involves conversion of N2 from the atmosphere into

ammonia (NH3)

- Industrial N2 fixation • Haber process.

• Atmospheric fixation and industrial fixation fix N2

into nitrate (NO3-).

b. Nitrification

• Conversion of ammonia(NH3) or ammonium(NH4+) to

nitrites(NO2-) and nitrates(NO3-).

• Ammonium(NH4+) formed when water reacts with

ammonia.

• Involve the role of nitrifying bacteria:

- Nitrosomonas and Nitrobacter

N2 NH3


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c. Assimilation

• Absorption of ammonia, ammonium or nitrate by roots.

• Incorporate the N2 into proteins, nucleic acids and

chlorophyll.

• When animals consume plant tissues, assimilate N2 by

taking in plant N2 compound and converting them into

animal N2 compound.

d. Ammonification

• Conversion of organic N2 compound into ammonia(NH3)

or ammonium(NH4+)

• Begins when excretion (urea) and nitrogen compound in

dead organisms are decomposed

• Releasing the N2 into the abiotic environment as

ammonia(NH3) or ammonium(NH4+)

• Done by ammonifying bacteria

e. Denitrification

• The reduction of nitrates(NO3-) to gaseous N2.

• Denitrifying bacteria reverse the action of nitrogen-fixing

and nitrifying bacteria.

• Return N2 to the atmosphere.


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Nitrogen Cycle

b. Illustrate

phosphorus

cycle.


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SUBTOPIC : 2.4 Conservation and Management

LEARNING OUTCOMES : a. Describe sustainable development.

b. Explain threats to biodiversity in Malaysia.

c. Illustrate conservation of diversity in Malaysia.

MAIN IDEAS


a. Describe

sustainable

development.

Sustainable development is development that meets the needs of

the present without compromising the ability of future generations

to meet their own needs.

1. Sustainable Agriculture

• Crop rotation • Contour farming • Strip farming • Terracing

2. Sustainable Forestry

• Cutting limits

growth


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MAIN IDEAS


• Forest reserves • Reforestation

3. Sustainable Fishery

• Leaves enough fish in the sea to breed and maintain future stocks and ensures the environment they live in is kept

healthy

b. Explain

threats to

biodiversity in

Malaysia.

1. Habitat loss due to land development.

• Habitat loss or conversion and economic exploitation of natural resources have been the primary cause of biological

diversity loss in Malaysia to date.

2. Deforestation.

• A direct cause of extinction and loss of biodiversity, due to logging and other human practices.

• Destroying the ecosystems on which many species depend.

3. Poaching.

• Poaching and other forms of hunting for profit increase the risk of extinction.

4. Overfishing.

• Fishing of juvenile fishes for the live reef fish trade increases the impacts of high fishing effort as well as commercial

fishing which lacks a proper management plan.

• Destructive fishing – Fish bombing and cyanide fishing are still carried out which affect coral reefs, mangroves and

coastal waters.

5. Pollution.

• Now more likely to be industrial pollution rather than habitat loss due to ongoing structural changes in the Malaysian

economy.

• Inevitably, the industrial sector is rapidly emerging as the major threat to biological diversity in the country.

• Industrial wastes that are incorrectly or indiscriminately disposed of will alter the abiotic condition of the ecosystem

and subsequently alter species composition in the area.

• Industrial pollution alters the ecosystem's chemical balance, the biological diversity and its capacity to support biological

forms.

Sources:

http://www.chm.frim.gov.my/About-CHM/Useful-Links-to-Bio-

Diversity/Threats-to-Biological-Diversity.aspx


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MAIN IDEAS


http://www.fishdept.sabah.gov.my/tagal.asp

c. Illustrate

conservation of

diversity in

Malaysia.

Conservation of Diversity in Malaysia

SUBTOPIC : 2.5 Population Ecology

LEARNING OUTCOME : a. Explain biotic potential and environmental resistance and their

effect on population growth.

b. Explain carrying capacity and its importance.

c. Describe natality and mortality and their effects on the rate of

population growth.

d. Explain population growth curves (state the basic forms of growth

curves):

i. Exponential growth curve (human)

ii. Logistic growth curve (Paramecium sp.)

e. Explain the limiting factors affecting the population size:

i. Density dependent factors

ii. Density independent factors

Ammonia

Nature reserves & National parks

(In-situ conservation)

Botanical gardens & Zoo

(Ex-situ conservation)

Planned land use


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MAIN IDEAS


a. Explain biotic

potential and

environmental

resistance and

their effect on

population

growth.

Population Ecology

The study of population in relation to their environment, including

environmental influences on population density and distribution, age

structure and variations in population size.

Population Growth

The increase in the number of individuals in a population.

- A population will increase in number when the available resources are greater than required at that particular time.

1. Biotic potential (r)

Maximum number of offspring an organism can produce under ideal

conditions.

- Biotic potential is the highest possible rate population increase (rmax), resulting from maximum rate of reproduction &

minimum mortality

- This is dependent on several factors: • The age beginning of reproduce • How often reproduction occurs • How many offspring are born at a time

- Ideal condition : • plenty of space for each member • unlimited resources • no resistance

- Important in population growth to sustain unlimited growth

2. Environmental resistance (K)

All those environmental conditions that prevent populations from

achieving their biotic potential.

- Interplay between biotic potential and environmental resistance determines the size of a population of a species.

- Exponential growth cannot continue for long because of environmental resistance.

- When populations become too large, will run out of some - limiting resource. - As a result, growth slows and population size tends to

stabilize.


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MAIN IDEAS


effect on

population

growth.

b. Explain

carrying capacity

and its

importance

Carrying capacity

The maximum population size that can be supported by the available

resources.

- Determined by both biotic potential and environmental

resistance.

- Changes in response to environmental changes.


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MAIN IDEAS


Importance of carrying capacity.

• Important limit on populations to prevent population crash

• Measured relative to a particular species and a particular

habitat

• A population below carrying capacity need not deplete any

natural capital.

c. Describe

natality and

mortality and

their effects on

the rate of

population

growth.

1. Natality (birth rate)

- The rate at which a particular species or population produces

offspring.

2. Mortality (death rate)

- The rate at which a particular species or population dies,

whatever the cause.

• Density is not a static property but changes as individuals are added or removed from a population.

• Additions occur through birth, while death will remove the individuals from a population.

• If the birth rate of a population increases, the population size will expand.

• If the death rate of a population increases, the population size will also decreases.

d. Explain

population


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MAIN IDEAS


growth curves

(state the basic

forms of growth

curves):

i. Exponential

growth curve

(human)

ii. Logistic

growth curve

(Paramecium sp.)

1. Exponential growth curve

Refers to unlimited growth of a population.

- Occurs when environmental conditions are not limiting. - Reproduce at maximum biotic potential. - Cause a large population growth.

- E.g.: human population growth

- Shows how the increase of individuals added each generation occurs exponentially due to:

• very productive agriculture. • raised the carriying capacity for humans. • inherited a high birth rate from ancestors.

2. Logistic growth curves

- S- shaped curve. - Is a result of environmental resistance which increases in

intensity as the population density increases until it reaches a

steady level.

- Achieve its maximum carrying capacity.


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MAIN IDEAS


- E.g.: Paramecium population - Population growth is stabilized by environmental resistance.

Divided into 4 phases :

Lag phase Paramecium prepares to grow , cell

division and differentiation of tissues

Log / Exponential

phase

Paramecium are growing, producing new

organisms and dividing rapidly to take

advantage of fresh medium

Transitional phase Growth slows down because of limited

nutrients.

Stationary phase

Birth of new organism and death of old

ones is in equilibrium. (natality =

mortality)

e. Explain the

limiting factors

affecting the

population size:

i. Density

dependent

factors

1. Density Dependent Factors

A limiting factor that depends on population size is called

a density-dependent limiting factor.

- Density-dependent limiting factors include: a. Competition

• When populations become crowded, organisms compete for food, water space, sunlight and other essentials.


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MAIN IDEAS


ii. Density

independent

factors

- Intraspecific competition An interaction in population ecology, whereby

members of the same species compete for limited

resources.

- Interspecific competition Individuals of different species compete for the

same resources in an ecosystem.

b. Predation • Populations in nature are often controlled by predation. • The regulation of a population by predation takes place

within a predator-prey relationship.

c. Parasitism • Parasites can limit the growth of a population. • A parasite lives in or on another organism (the host) and

consequently harms it.

d. Territorial behavior • Animal defending land from other member of a species. • Animal defend their territories for:

- food - shelter - mates

2. Density Independent Factors

Refers to any characteristic that is not affected by population

density.

- Density-independent limiting factors affect all populations in

similar ways, regardless of the population size.

- Examples of density-independent limiting factors include:

• unusual weather

• natural disasters

• seasonal cycles

• certain human activities—such as damming rivers,

pesticides, and clear-cutting forests

CHAPTER 2: ECOLOGY...CHAPTER 2: ECOLOGY SUBTOPIC : 2.1 Ecosystem Concept LEARNING OUTCOMES : a. Define ecosystem. b. Describe lake ecosystem based on: i. light penetration (photic

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