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Form 2 Form 2

Science Chapter 4Science Chapter 4

Interdependence among LivingInterdependence among Living

Organisms and the EnvironmentOrganisms and the Environment

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Content

1. Interdependence Among Living Organisms

2. Interaction Between Living Organisms

3. Food Webs

4. Photosynthesis

5. The Importance of The Conservation and Preservation Of Living Organisms

6. Role of Man in Maintaining the Balance in Nature

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4.1 4.1

Interdependence Among Interdependence Among

Living OrganismsLiving Organisms

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Habitat

• A habitat is the natural living place of natural living place of

plants and animals.plants and animals.

• A habitat provides an organism with air, space, food, shelter and a place in which to breed.

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Species

• A species is a group of organisms that have the same shape and structure.

• They can also breed together to produce can also breed together to produce

offspring that are fertile.offspring that are fertile.

• Penguins , rat, cat and elephant are examples of the different species of organisms.

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Population

• A population is a group of organisms comprising the same species that live together in a habitat.

• For example,

(a) a population of monkeys

in a tree

(b) a population of elephants

on a grassland

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Community

A community consists of

several speciesseveral species of animal and plant population that live together and interact with one another in a habitat.

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Ecosystem

• An ecosystem consists of several several

communitiescommunities that interact with one another and with the physical environment (non-living things such as water, air, soil, light and mineral salts).

• For example,

(a) a pond ecosystem

(b) a tropical rainforest ecosystem

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Learn more :

http://www.youtube.com/watch?v=XJ6VtduDSyY&feature=related

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4.24.2

Interaction BetweenInteraction Between

Living OrganismsLiving Organisms

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1. Prey-predator

• A predator is an organism that kills and eats another organism.

• A prey is the organism that is eaten.

predator

prey

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1. Prey-predator

• A predator usually has special physical characteristics such as sharp claws and fangs, or a sharp beak, with which to kill its prey.

• A prey usually has the ability to run away a from a predator.

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Symbiosis

• Symbiosis basically

means ‘living together’ .

• There are three types of

symbiotic relationships,

namely

i. Commensalism

ii. parasitism and

iii. mutualism.

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I .Commensalism (Symbiosis)

• In commensalismone species benefits from the interaction, as the other is unaffected.

• The unaffected species is the host.

Staghorn fern obtains sunlight,

Tree is not effected .

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I .Commensalism (Symbiosis)

remora and the shark

The anemonefish lives among the

forest of tentacles of an anemone

and is protected from potential

predators.

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ii. Parasitism (Symbiosis)

• Parasitism is another type of interaction between two organisms.

• Only one organism benefits.

• The other organism suffers some disadvantage.

Rafflesia absorb minerals from roots

of other plants.

Louse suck blood

from their

host

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ii. Parasitism (Symbiosis)

• A parasite is an organism that lives on or inside the other organism.

• The host is the organism on or in which the parasite lives.

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Two groups of parasites :

2. Parasites that live

inside the host

organism.

• For example,

tapeworms and

hookworms inside the

intestines of humans

and animals.

1. Parasites that live

out side the host

organism.

• For example

mosquitoes, lice and

fleas suck blood

from their host .

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iii. Mutualism (Symbiosis)

• In mutualism, the interaction is beneficial to both species.

• Mutualism is a form of cooperation.

• They obtain nutrition and shelter from each other.

The bird eats the fragments of food left

between the crocodile teeth.

So the crocodile gets its teeth cleaned.

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iii. Mutualism (Symbiosis)

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Competition

• Competition occurs when organisms compete for the same basic resources.

• Animals compete to obtain water, food, living space and mates for reproduction.

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Competition

• Plants compete to obtain water, sunlight, minerals and living space.

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Summary so far ...

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Biological control

• Biological control is a method in which a predator, the natural enemy to a certain pest, is used to control the population of that pest in an area.

The aphid is a pest to the

gardeners, damaging his

plants.

The ladybirds helps the

gardener by ridding him of

these pests

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Biological control

• Biological control has many advantages as compared with using pesticides.

• Some of them are:

(a) it does not pollute the environment

(b) it does not kill other organisms except

the pests

(c) it is cheap and safe to use

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Biological control

Barn Owls (Tyto alba) a

proven natural predator

of rats in Oil Palm

When the eggs hatch,

the ichneumon larvae

feed on the body of the

host .

Biological weed

control involves the

release of

organisms that

attack plants to

control weeds.

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4.34.3

Food WebsFood Webs

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Food Chain

• A food chain is an energy flow showing how

energy in food is passed from plants (producers)

to animals (consumers).

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Food Webs

A food web consists of several food chains that

are interlinked to one another

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Pyramid of numbers

• A pyramid of numbers shows the number of organisms at each stage of the food chain.

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Pyramid of numbers

• From the base of the pyramid to its peak:

(a) the number of organisms decreases

(b) the size of the organisms increases

(c) more energy is lost

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4.44.4

Photosynthesis Photosynthesis

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• Photosynthesis is a process that occurs in green plants, in which food is madefrom water and carbon dioxide in the presence of chlorophyll and sunlight.

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Photosynthesis equation

Carbon dioxide

water

chlorophyll

sunlight

Glucose

(food)oxygen

The glucoseglucose produced is transported to

other parts of the plant to be:

(a) oxidised through the process of

respiration to provide energy

(b) stored as starch

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The role of photosynthesis

a) enable green plants to make their own

food.

b) regulate and maintain carbon dioxide

content in the atmosphere.

c) increase oxygen content in the

atmosphere.

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Experiment 1 break the

cells.

remove chlorophyll

soften the

leaf

Test for starch .

Turn blueblue--black.black.

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Experiment 2

Aim :

To show plant need carbon dioxidecarbon dioxide for photosynthesis .

Info :

Sodium hydroxide absorbs carbon dioxide

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The carbon cycle

• The carbon cycle is the circulation of the circulation of the

carbon element on the Earthcarbon element on the Earth..

• These processes take place continuously.

• The carbon cycle maintains the content of carbon dioxide in the air.

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The carbon cycle

• The processes that release carbon dioxiderelease carbon dioxideinto the air include:

(a) respiration and breathing

(b) combustion

(c) decomposition

• Photosynthesis, which takes place in green plants, removes carbon dioxideremoves carbon dioxide from the air.

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The oxygen cycle

• The oxygen cycle is the circulation of oxygen on

the Earth.

• These processes take place continuously.

• The oxygen cycle maintains the content of

oxygen in the air.

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The oxygen cycle

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4.54.5

The Importance of The The Importance of The

Conservation and Preservation Conservation and Preservation

Of Living OrganismsOf Living Organisms

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The greenhouse effect

• The greenhouse effect occurs because a layer

of carbon dioxidecarbon dioxide in the atmosphere prevents a

portion of heat from escaping to the outer space.

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The greenhouse effect

• The greenhouse effect raises the Earth's temperature.

• This is known as global warmingglobal warming.

• This phenomenon causes changes in the world's weather and climate.

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Result of global warming

The sea level increases and this results inthe flooding of low-Iyingcoastal areas.

The melting of icecaps at both of the Earth's poles.

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The depletion of the ozone layer

• The ozone layer absorbs most of the ultraviolet rays before it reaches the Earth's surface.

• Chemicals such as chlorofluorocarbonschlorofluorocarbons (CFCs), used in the manufacture of aerosol sprays, refrigerators and air conditioners, are pollutants that break down the ozone molecules in the ozone layer.

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Ozone hole

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Ozone depletion effects

• Ultraviolet rays that reach the Earth cause:

(a) skin cancer

(b) cataract of the eyes

(c) the human immune system to

malfunction

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Acid rain

• Gases such as sulphur dioxide and nitrogen dioxide dissolve in rainwater to form acid rain.

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Acid rain effects

Acid rain can:

a) destroy sculptures .

b) lower the soil pH value and make it unsuitable for plants.

c) River water that is polluted by acid rain is no longer suitable for aquatic organisms.

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4.64.6

The Importance of The The Importance of The

Conservation and Preservation Conservation and Preservation

Of Living OrganismsOf Living Organisms

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• Managing environmental pollution can save our Earth.

• The following are steps that can be taken to reduce environmental pollution:

(a) use unleaded petrol

(b) ban nuclear testing

(c) create special places to burn rubbish

(d) implement stricter law enforcement on the

disposal of toxic waste from factories

(e) hold campaigns to prevent pollution

(f) recycle, reuse and reduce materials