CHAPTER 4INTERDEPENDENCE

AMONG LIVING ORGANISMS AND THE

EVIRONMENT1

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.

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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 lives7. Non living organisms in an environment

include air, water, sunlight and soil.

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Carbon dioxide

Oxygen Phot

osyn

thes

is

Resp

iratio

n

Sun

Plant Food

Absorption

Rat

Bacteria and fungi

Death

Death

Death Decomposition

Food

Snake

Minerals

figure 4.1

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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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Types of interaction1. 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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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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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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4.3 Food web1. Producers are green plant that produce their own food

by photosynthesis2. Consumers are organisms that eat other organisms as

food3. A primary consumers is usually a herbivore and feeds

on plants4. A secondary consumer feeds on the primary

consumers5. A tertiary consumer feeds on the secondary consumers6. Decomposers are organisms that breakdown dead

plants and animals into simpler substances like nitrates. They are made up of bacteria and fungi

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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

Decomposers Nitrates

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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.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.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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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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• 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

Animals Plants

Carbon dioxide

respiration respiration

photosynthesis

photosynthesis

decompositioncombustionOf fuel

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• 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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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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• 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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• 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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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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• 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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