PS AR RSO P6L24 Revision 2 WS

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Topic: REVISION 2 (LESSON 24)

REVISION 2 (LESSON 24)

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Lesson Outline

• Notes
• Open-ended Questions

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– NOTES

Fill in the blanks using the word bank below:

community
ecosystem
consumer
population
aquatic
producer
limiting factor
decomposers
apex predator

1. A(n) is the top consumer in a food chain.

2. A does not need other living things to survive or produce

energy.

3. All members of one kind of organism that live in a particular area are called a
.

4. A group of different populations of organisms is called a .

5. An organism that needs to eat/prey on other organisms to survive is called a
.

6. A habitat involving both the biotic and abiotic factors is .

7. Consumers that break down dead or decaying matter are .

8. A water-based ecosystem is .

9. A condition or resource that keeps a population at a certain size is known as a
.

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– NOTES

Living together

• An organism is a living thing.

• The of an organism includes all the factors that affect the survival

of that of that organism.

Environment

Physical characteristics Other factors

Availability
of food

• Organisms are often found living in groups with other organisms of the same kind.

•A consists of all the organisms of the same kind that live and

reproduce in a particular place.

•E.g. all the water hyacinth floating on a pond makes up the water hyacinth

population of the pond.

• The is the total number of live organisms in a population.

Adults and must be counted when counting the population size.

• The place where a population of organisms lives in called its . It

provides the organisms living there with everything they need to stay alive.

• All the different populations of organisms living together in a habitat form a

.

• All the populations living in a habitat are linked together. They may depend on one

another for survival, or for completing their life cycle. Populations living in the same

habitat are therefore said to be .

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– NOTES

The Environment

• Organisms are affected by conditions in their surroundings.

• Our environment is affected in a lot of ways by different factors. In the study of ecology,

we generally term such factors as or .

The characteristics of an environment include:

• Temperature • Soil • Food
• Other organisms
• Air • Light

• Water

Unfavourable Environments

• The environment in a habitat can suddenly change (eg. introduction of new organism,
fire or flood) so that it is difficult for organisms in that habitat to survive. The new
environment is unfavourable for organisms living in that habitat.

• The organisms living in the unfavourable environment may die or move away from
their habitat.

• Some organisms may be able to survive the unfavourable environment. For example,
snakes may be able to swim in the water of the flood and not drown or birds can fly high
above flames to avoid smoke and heat.

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Food Chains and Food Web

• are
are
organisms that can make their own food. All
producers, therefore food chains/webs always start with them.

• are organisms that cannot make their own food. They feed on
plants or other consumers.

• A food chain shows the between organisms.

• Food chains are also energy chains because they show the
between organisms.

Predator – Prey relationship

• Predators control the number of prey in a community by killing them.

• Prey controls the number of predators in a community because they are food for the
predators.

• The population sizes of predators and prey stay balanced in a community.

• Removing or adding a population of organisms upsets the balance in a community.

• Not all carnivores are predators. For example, vultures and hyenas feed on the remains

of other carnivores’ prey. They are known as .

Decomposers

• When plants and animals die, they become food for other organisms called
decomposers, e.g. bacteria and fungi

• Decomposers get their food by breaking down dead organisms and waste matter into

substances such as and . This

process is called or decay.

• Note: Some organisms such as earthworms, snails, millipedes and termites help
decomposers by biting or breaking up dead organisms or waste matter into smaller
pieces but they are not decomposers!

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Adaptation

• Organisms often have special characteristics or features that help them to
o Survive in their natural habitats or
o Reproduce

These special characteristic are called adaptations.
• An organism that is adapted to the environment in its natural habitat can survive

there.

Types of Adaptations

• adaptation
o Some organisms have special body parts or unusual life processes that help them
survive or reproduce.

• adaptation
o Some organisms behave in certain ways that help them survive or reproduce.

• Organisms may have both structural and behavioural adaptations to help them survive
or reproduce

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Activity 1 – Open-ended Questions
1. Sea urchins are sea animals that have long spikes with venomous sting. However, they

move very little.
Animal G is a sea animal that can pick up objects to carry on its shell.

Sea urchin Animal G

(a) Animal G can sometimes be seen carrying sea urchins on its shell. [1]
State how this behavior can benefit both animals for survival.

The Cardinalfish shown below will carry its young in its mouth to look for sea urchins to
place the young among the spikes of the sea urchin.

Cardinalfish [1]
(b) Explain how its action can help to ensure the survival of its young.

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2. The diagram below shows a mangrove habitat. The water level in this habitat rises and
falls throughout the day.

The following shows the relationship between the organisms:
plant X  animal Y  animal Z

(a) From the diagram, list two adaptations of animal Z and how they help it to hunt for

food. [2]

(b) Animal Y lives underground but can climb trees. Give two reasons why climbing trees

can help animal Y survive in the mangrove habitat. [2]

(c) State one way plant X can benefit from animal Y [1]

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3. A test-tube containing hot water at 50°C was placed in a beaker of cold water at 20°C as
shown below.

test-tube of hot water at 50°C

beaker of cold water at 20°C

After 20 minutes, both temperatures of water in the test-tube and the beaker were
measured and recorded in the table below.

water in the test-tube Temperature (°C)
water in the beaker 35
27

(a) What causes the above changes in the temperatures of water in the test-tube and

the beaker? [1]

Steven saw bird P waiting to catch its prey in the pond. He observed that bird P
stood on only one leg in the cold pond water while doing so.

bird P standing on one leg

(b) Steven’s teacher explained that standing on one leg in the cold water instead of two
is a behavioural adaptation for bird P to conserve body heat. Explain how this is so.
[1]

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Steven also observed that when bird P slept, it puffed up its feathers, tucked its head
and placed the non-standing leg into its feathers as shown below.

heads tucked
among the
feathers

standing on one leg with
the non-standing leg in

the feathers

(c) Explain how this behavioural adaptation helps to keep bird P warm in cold weather.
[2]

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4. Graphs 1 and 2 show the average temperature and the average sea level rise on Earth
over the years.

Graph 1

average
temperature

1990 2017 year

Graph 2

average sea
level rise

1990 year
2017

(a) Using both graphs 1 and 2, explain the relationship between the average [2]
temperature and the average sea level rise on Earth.

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Organism Z lives in the sea but lays its eggs on land near the sea coast.
sea
sea coast

(b) Using the information from graphs 1 and 2, what will happen to the population of

organism Z over time? Explain why. [CER] [2]

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