Page 37 - LIFE_&_LIVING_BK4_4thPages.indd

Activity 4 Decide together: Threats to an
ecosystem

Time: 45 minutes
Objectives

By the end of the lesson learners should be able to:
• understand balanced and unbalanced life in an ecosystem Resources
• identify possible threats to an ecosystem and possible ways to
overcome them • Newsprint
• Kokis
• Learner task sheet
Teacher guidelines

1. This lesson aims to explore what happens in an ecosystem
if one or more organisms are removed (from hunting for
example, or a disease).

2. Put one of the food webs used in the previous activity on the
board and pose the scenario that the a herbivore has become
extinct. Place a piece of blank paper over the herbivore.

3. Ask learners how this affects the other organisms in the food
web. (The other organisms cannot survive without their food
source.)

4. Now explain that a producer has been killed by a herbicide.
Cover the producer.

5. Ask the learners how this affects the other animals.
(The other organisms cannot survive without their food source.)

6. Conclude this discussion by explaining that life in any
ecosystem is in a delicate balance and changing one
organism in a food web can alter that balance. Ensure
learners understand that all plants and animals are linked and
depend on each other and their environment.

7. Divide learners into groups. Give each group a sheet of
newsprint and ask them to divide it into two columns,
headed ‘Threats’ and ‘Solutions’.

8. Ask learners to brainstorm all the ways they can think of in
which humans threaten ecosystems. Possible ideas would
include: habitat destruction for building houses, roads,
dams, for agriculture, deforestation, hunting, overfishing, by
polluting water and soil, by introducing other alien species
into an area, etc.
Then they should think about ways in which these problems
could be overcome and write these in the ‘solutions’ column.
Possible ideas would include organic farming, laws, higher
density housing, water harvesting, alien vegetation removal,
limiting hunting and fishing, etc.

9. Hand out the learner task sheets to be completed
individually.

Life and living | Ecosystems and food webs 37

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