2. 4.1 Interdependence among living
organisms
1. A species is a group of the same kind of
organisms with common characteristics.
2. A population refers to the group of organisms
of the same species living and reproducing in
a defined area.
3. A community is made up of different
populations of organisms living together in a
habitat.
4. The organisms in a community depend on
one another for food, shelter and protection.2
3. 5. An ecosystem consists of plants, animals and
the non living environment.
ecosystem= living organisms + non living
environment
= community + habitat
6. A habitat is a place where an organisms lives
7. Non living organisms in an environment
include air, water, sunlight and soil.
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5. 8. Refer to figure 4.1 the interdependence
among living organisms and the environment
creates a balanced ecosystem.
– During respiration, living organisms take in
oxygen and give out carbon dioxide.
– During photosynthesis, plants take in carbon
dioxide and give out oxygen.
– Plants make food using carbon dioxide from air
and water from the soil with the help of light
energy from the sun and chlorophyll in their
leaves.
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6. Types of interaction
1. Prey-predator
(a) predator - animals that hunt other animals for food.
(b) prey - the animals being hunted.
2. Symbiosis
(a)commensalism - a relationship between two organisms such that one benefits fro it
while the other neither benefits nor is harmed by it.
(b)mutualism – an association between two organisms such that both sides benefits
from the relationship.
(c)parasitism – association between two organisms such that one organisms benefits
and the other is harmed.
3. Competition
an interaction among organisms competing for the same basic needs.
4.2 Interaction between living organisms
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7. 1. Interaction between living organisms is important as it
helps to maintain the size of populations in an
ecosystem. Hence, this will maintain a balanced
ecosystem
2. In any ecosystem, when a population grows too big, the
organisms of the same species will complete among each
other for their basic needs
3. Some will die and this will reduce the size of the
population and maintain a balanced ecosystem
4. Biological control is the control of pests by the
introduction of their natural enemy
examples of biological control
(a) fishes(predator)eat the larvae(prey)of mosquitoes in
the pond
(b) owls(predator)eat the rats(prey)in the oil palm
estates
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8. 5. The advantages of using biological control are
- the population of crop pests can be controlled
- it is free from pollution
- other populations are not affected
- it is cheap to maintain
6. the disadvantages of using biological control are
- the time taken to control the pests is long
- the predator may escape and upset the food
chain
- the increase in the number of predators may
become a nuisance to the community, such as
the crow problems in klang
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9. 4.3 Food web
1. Producers are green plant that produce their
own food by photosynthesis
2. Consumers are organisms that eat other
organisms as food
3. A primary consumers is usually a herbivore and
feeds on plants
4. A secondary consumer feeds on the primary
consumers
5. A tertiary consumer feeds on the secondary
consumers
6. Decomposers are organisms that breakdown
dead plants and animals into simpler substances
like nitrates. They are made up of bacteria and
fungi 9
10. 7. A food chain is series of living organisms
arranged such that each organisms feeds on
the one below it in the series
8. Food wed is made up of two or more
interconnected food chains
plants
(produces)
Animals
(consumers)
Death
Excretory waste
DecomposersNitrates
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11. 9. Pyramid of numbers is a diagram showing the
relative number of organisms at each level of
a food chain
10.The amount of energy transferred from one
level to the higher level in a pyramid of
numbers decrease
11.Some energy is lost as heat
Snake
(tertiary
Consumer)
Frog
(secondary consumer)
Grasshopper
(primary consumer)
Grass
(producer)
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12. 12.If there is a drastic change in any of the
populations of living organisms in the
ecosystem, it will upset the whole ecosystem
Plants
Sparrow Grasshopper Butterfly Pigeon
Frog
Snake 12
13. 13.If the population of the grasshopper in
figure increase
= the population of frog will increase
= the population of snake will increase
= the population of plants will decrease
14. When one population in the food web is
mising, decrease or increase, the food web
will be imbalanced. It will take a long time for
the ecosystem to balanced again
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14. 4.4 Photosynthesis
• Photosynthesis is the process of making food by
green plants ( producers ).
• Chlorophyll (green pigment) in leaves absorb light
energy from the sun.
• In the presence of sunlight and chlorophyll, green
plant use water and carbon dioxide to make food
i the form of glucose. Oxygen is released.
• Plant need light, chlorophyll, carbon dioxide and
water for photosynthesis. Photosynthesis will not
take place if any of the factors is absent.
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15. • The oxygen cycle
- oxygen is released during photosynthesis
- oxygen is used up during respiration by plants and
animals
- oxygen is used up during decomposition by micro-
organism.
- oxygen is used up during burning of fuels.
Oxygen
AnimalsPlants
Carbon dioxide
respiration respiration
photosynthesis
photosynthesis
decomposition
combustion
Of fuel
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16. • The carbon cycle
- carbon dioxide is released during respiration,
combustion and decomposition.
- carbon dioxide is removed from the air
during photosynthesis.
Carbon dioxide in the air
Animals
Fossil fuels
Green plants
respiration
combustion
decomposition
decomposition
photosynthesis
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17. 4.5 Evaluating the Importance of Conservation
and Preservation of Living Organisms
• Conservation means maximizing the use of
natural resources with the least disturbance to
the living organisms and their environment.
• Preservation refers to the measures taken to
maintain living organisms and the
environment in their natural balanced state.
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18. • Steps taken to conserve and preserve living
organisms :
- Build more centres for the endangered species
to reproduce.
- Establish more forest reserves and national
parks.
- Controlling deforestation and extensive fishing.
- Recycling.
- Enforce laws to control logging activities
- Enforce laws on the protection of wildlife.
- Increase public awareness on its importance
through education.
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19. • The importance of conservation and
preservation of living organisms:
- Maintain nature’s balance
- Preventing extinction of endangered species
- Helps to promote eco-tourism.
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20. 4.6 Role of Man in Maintaining the
Balance in Nature
• The effects of human activities on the balance in
nature:
- Change of global climate
- Destruction of habitat
- Extinction of species
- Air, soil and water pollution
- Deforestation
- Over usage of land
- Over fishing
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21. • Steps taken to solve problems related to
environment:
- Establish more forest reserves and replant
trees
- Do not pollute the air, soil and water as the
pollutants are harmful to the organisms
- Enforce laws on illegal hunting
- Support wildlife preservation
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