1.A species is a group of the same kind of organisms with common characteristics.
2.A population refers to a 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.
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 in an environment include air, water, sunlight and soil.
7.Food chain shows the feeding relationship between organisms.
Producer→ Primary consumer→ Secondary consumer → tertiary consumer
8.Food web is composed of the combination of a few food chain.
9.Pyramid number represents the comparison of the number of organisms in a food chain.
(a) The higher the level of the pyramid number, the smaller the number of organisms.
(b) The higher the level of the food pyramid, the smaller the energy transferred.
10.Preservation and conservation of organisms are important to provide a balance ecosystem.
(a) Preservation - Maintain living things in their nature condition.
(b) Conservation - Restore, conserve and protect living organisms from extinction.
11.Types of interaction between organisms are as follows:
12. The interdependence among living organisms and the environment creates a balanced ecosystem.
(a) During respiration, living organisms take in oxygen and give out carbon dioxide.
(b) During photosynthesis, plants take in carbon dioxide and give out oxygen.
(c) Plants make food using carbon dioxide from the air and water from the soil with the help of light energy from the Sun and chlorophyll in their leaves.
13.
14.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.
15.In any ecosystem, when a population grows too big, the organisms of the same species will compete among each other for their basic needs.
16.Some will die and this will reduce the size of the population and maintain a balanced ecosystem.
17.Biological control is the control of pests by the introduction of their natural enemy.
Examples of biological control:
(a) Fish(predator) eat the larvae (prey) of mosquitoes in a pond.
Oil palm→ Rat →Owl
tree (Prey) (Predator)
(b) Owls (predator) eat the rats (prey) in the oil palm estates.
(c) Grass is planted to control the growth of weeds in the garden. (The weeds compete with the grass.)
18.The advantages of using biological control are
(a) the population of crop pests can be controlled
(b) it is free from pollution
(c) other populations are not affected
(d) it is cheap to maintain
19.The disadvantages of using biological control are
(a) the time taken to control the pests is long
(b) the predator may escape and upset the food chain
(c) the increase in the number of predators may become a nuisance to the community.
4.3 Food Web
1. Producers are green plants that produce their own food.
2. Consumers are organisms that eat other organisms as food.
3. A primary consumer 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.
7. Pyramid of numbers is a diagram showing the relative number of organisms at each level of a food chain.
8. The amount of energy transferred from one level to the higher level in a pyramid of numbers decreases.
9. Some energy is lost as heat.
10. If there is a drastic change in any of the population of living organisms in the ecosystem, it will upset the whole ecosystem.
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| Food web |
(a) The population of the frog will increase
(b) The population of the snake will increase
(c) The population of the plants will decrease
12. When one population in the food web is missing, decrease or increases, the food web will be imbalanced. It will take a long time for the ecosystem to be balanced again.
4.4 Photosynthesis
1.Photosynthesis is the process of making food by green plants (producers).
2.Chlorophyll (green pigment) in leaves absorbs light energy from the Sun.
3.In the presence of sunlight and chlorophyll, green plants use water and carbon dioxide to make food in the form of glucose. Oxygen is released.
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Glucose (food)- Converted into starch
Oxygen - Released into the air
Water - Absorbed by roots
Sunlight - From the Sun
Carbon dioxide - Enters the leaves through the stomata
4. Plants need light, chlorophyll, carbon dioxide and water for photosynthesis. Photosynthesis will not take place if any of the factors is absent.
5. In order to know whether photosynthesis has taken place, we test for the presence of starch in leaves.
6. The presence of starch can be tested using iodine solution when the chlorophyll in the leaf is removed.
7. The area containing starch will turn dark blue when iodine solution is added.
8. The oxygen cycle
(a) Oxygen is released during photosynthesis.
(b) Oxygen is used up during respiration by plants and animals.
(c) Oxygen is used up during decomposition by microorganisms.
(d) Oxygen is used up during burning of fuels.
9.The carbon cycle
(a) Carbon dioxide is released during respiration, combustion and decomposition.
(b) Carbon dioxide is removed from the air during photosynthesis.
4.5 The importance of Conservation and Preservation of living Organisms
1. Conservation means maximising the use of natural resources with the least disturbance to the living organisms and their environment.
2.Preservation refers to the measures taken to maintain living organisms and the environment in their natural balanced state.
3.Steps taken to conserve and preserve living organisms:
(a) Build more centres for the endangered species to reproduce
(b) Establish more forest reserves and national parks
(c) Reforestation
(d) Controlling deforestation and extensive fishing
(e) Recycling
(f) Enforce laws to control logging activities
(g) Enforce laws on the protection of wildlife
(h) Increase public awareness on its importance through education
4. The importance of conservation and preservation of living organisms:
(a) Maintaining nature's balance
(b) Preventing extinction of endangered species
(c) Helps to promote eco-tourism
4.6 Role of Man in Maintaining the Balance in Nature
1.The effects of human activities on the balance in nature:
(a) Change of global climate
(b) Destruction of habitat
(c) Extinction of species
(d) Air,soil and water pollution
(e) Loss of wetlands
(f) Solid waste management
(g) Deforestation
(h) Over usage of land
(i) Over fishing
2. Steps taken to solve problems related to environment:
(a) Establish more forest reserves and replant trees
(b) Do not pollute the air, soil and water as the pollutants are harmful to the organisms
(c) Enforce laws on illegal hunting
(d) Support wildlife preservation
(e) Enforce laws concerning disposal of toxic wastes to the environment
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