1. Chapter 22 Our Impact on the Ecosystem (Part 2)

2. Objectives Students should be able to Outline the roles of microbes in sewage disposal as an example of environmental biotechnology Discuss reasons for conservation of species with reference to maintenance of biodiversity, management of fisheries and management of timber production

3. 16 October 2015 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 3 Reasons for Conservation (b) Tropical plants provide raw materials for medicinal drugs, e.g. quinine from the bark of Cinchona, and morphine, from the sap of the poppy plant, and natural insecticides, e.g. pyrethrum, the chemical found in chrysanthemum. Certain poisonous animals in the rainforest may contain chemicals that have medicinal value. (c) Tropical rainforests provide food, e.g. rice, pineapple and banana. (a) Tropical plants provide raw materials for industries, e.g. rattan to make furniture, rubber to make tyres, fibres from cotton plants to make cloth, and fibres from coconut husks to make ropes. To maintain biodiversity. Rainforests house a large number of species of animals and plants. Many tropical plants are of great economic importance as they are sources of raw material for industries, medicinal drugs, natural insecticides and food. 7 2 To maintain a stable and balanced ecosystem. Prevents disruption of natural cycles, e.g. water and carbon cycles. Prevents global warming. To prevent the extinction of plant and animal species. 1 To ensure the conservation of marine life, as they are a major source of human food. Conservation preserves natural scenery and wildlife for people to appreciate. It also maintains natural resources for outdoor recreational activities, e.g. fishing, hiking and skiing. 43 To maintain a large gene pool. Many wild plants and animals possess favourable genes. By cross-breeding the different varieties of wild plants and animals, we can improve agricultural produce, e.g. gaining a better yield of milk or producing plants with better resistance to diseases and drought. 6 Conservation is of scientific value. The study of wildlife provides useful information to humans, e.g. we learn about evolution from studying wildlife. 5 REASONS FOR CONSERVATION

4. Conservation measures Indirectly through human population control and reducing or eliminating pollution Directly through conserving natural resources Protecting wildlife

5. Environmental Biotechnology This involves making use of biological science to provide environmentally friendly to reduce pollution and keep the environment clean.

6. Decomposers in Sewage Treatment Decomposition of sewage takes a long time Hence, sewage is drained into large settling tanks Bacteria present in the sewage secrete enzymes to digest it Bacteria also feed on such digested products Liquid that results are filtered before being discharged into sea Digested solid are dried and used as fertilisers E.g. of environmental biotechnology

7. (a)Sewage from household is drained into settling tanks, and then into sedimentation tanks. (b)In the aeration tank Bacteria mixed with sewage Bacteria secrete enzymes to digest the solid organic waste in the sewage into harmless soluble substances and CO 2. Bacteria also feed on these products (c)Liquid and disease-causing microorganisms are removed and filtrate is discharged into the sea. Solid remains is known as sludge (d)Anaerobic bacteria breakdown organic matter in the sludge (e)Sludge is removed, dried and used as fertilisers.

9. How do we conserve the forests?  Prevention of massive cutting down of forests  Laws that ensure that trees for timber are cut down selectively and at a regulated rate

10. How to conserve fishing grounds?  Banning the use of drift nets which trap all forms of marine nets  Using nets with a certain mesh size so that young fish are not caught  Regulating the entry of ships into fishing grounds  Limiting the period of fishing in fishing grounds  Eliminate pollution of rivers and seas