Forests: Our Lifeline

A forest is a system of plants, animals and micro-organisms. Its trees form layers: the branchy upper part of a tree is its crown, the crowns of tall trees together form a roof called the canopy, and below them grow shrubs and tall grasses forming the understorey, with herbs, mosses and dead leaves on the forest floor. Forests provide homes for many animals, and they are linked by food chains such as grass -> insects -> frog -> snake -> eagle, which together form a food web. Decomposers such as fungi and bacteria break down dead plants and animals into dark, nutrient-rich humus. Forests are called our lifeline because they keep the balance of oxygen and carbon dioxide, help bring rainfall through the water cycle, protect soil from erosion and reduce floods by soaking up rainwater like a sponge. They also give us timber, medicines, gum, honey, fruits and fodder, and support forest-dwelling communities. Deforestation causes soil erosion, floods, droughts, climate change and loss of wildlife, so forests must be conserved for the future.

Detailed Worksheet: Forests: Our Lifeline Section A - Definitions (10 marks) 1. What is a forest? Name its three main components. (2 marks) 2. Define crown and canopy of trees. (2 marks) 3. What is the understorey of a forest? Give examples of plants found there. (2 marks) 4. What is humus? How is it formed? (2 marks) 5. What are decomposers? Name two. (2 marks) Section B - Calculations and Applications (15 marks) 6. List six products we get from forests and the use of each. (3 marks) 7. Arrange the following organisms into a food chain: frog, grass, eagle, insect, snake. Name the producer and the top consumer. (3 marks) 8. Explain how forests help in (i) bringing rain (ii) preventing floods (iii) preventing soil erosion. (3 marks) 9. Why are forests called the "lungs" of the Earth? Explain the role of photosynthesis in this. (3 marks) 10. Give three reasons why the forest floor is dark and moist, and why dead leaves there do not pile up for ever. (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram showing the different layers of a forest: canopy, crown of an emergent tree, understorey (shrubs and tall grasses), herbs and forest floor. (4 marks) 12. Draw a food web involving at least six forest organisms, using arrows correctly. (3 marks) 13. Draw a cycle diagram showing how forests take part in the exchange of oxygen and carbon dioxide between plants and animals. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. A large forest near a town is cut down to build factories. (i) What changes will occur in the rainfall of the area? (ii) What will happen to the soil? (iii) What may happen to wild animals? (iv) How would the air quality change? (v) Suggest two ways to reduce the damage. (5 marks) 15. Explain why a forest is called a dynamic living entity. (i) Why is it said "nothing goes waste" in a forest? (ii) How does a forest regenerate? (iii) What is the role of animals in dispersing seeds? (iv) How do decomposers help plants? (5 marks) 16. Forest-dwelling communities depend on forests for food, shelter and livelihood. (i) Name two products they collect. (ii) How do they help in conserving forests? (iii) What problems do they face when forests are cut? (iv) Suggest one policy to protect both people and forests. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Use arrows in food chains to point from the food to the eater.