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Biology Student’s Companion Resources SB025
1 | KMPk
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
/KEY POINT EXPLANATION NOTES
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
/KEY POINT EXPLANATION NOTES
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
Advantages Disadvantages
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.
Advantages Disadvantages
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
/KEY POINT EXPLANATION NOTES
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
/KEY POINT EXPLANATION NOTES
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
/KEY POINT EXPLANATION NOTES
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
/KEY POINT EXPLANATION NOTES
• 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
/KEY POINT EXPLANATION NOTES
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
/KEY POINT EXPLANATION NOTES
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
/KEY POINT EXPLANATION NOTES
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
/KEY POINT EXPLANATION NOTES
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
/KEY POINT EXPLANATION NOTES
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
/KEY POINT EXPLANATION NOTES
- 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
/KEY POINT EXPLANATION NOTES
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