Answers

Objective Questions

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Structurcd Question

(a) Population : Number caught and marked x Number recantured|{umber marked at the second capture

(b) (i) Yes(ii) Number of pests s decreases 3 w-eeks after predator T is introduced

(c) (i) Deteriorates(ii) Because its food, which is pest S has decreased

(d) 1 Predator T is specific for pest S, that is predator T does not damage vegetables2 The population of predator T can be controlled naturally

(e) I Is not removed easily2 Does not attract the attention of the predator

(f) Chemical substances such as insecticide

Essay Question(a) The first organism to colonise a barren area is usually plants.

(b) 4 adaptation characteristics ofapioneer is:I Fibrous root system to absorb a lot of water quickly2 Succulent leaves to store water3 Produce a lot of small and light seedlings so that they can be dispersed by the

wind4 Creeping stems so that an a.rea can be colonised quickly

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Structured Question(a) 20km(b) (t) Poiiution of the river water reduces the number of fish, decreases the concentration

of dissolved oxygen in the water and increase the number of bacteria.(ii) Domestic waste disposal / rvaste materials

(c) 1 Lorv rate of fish reproduction2 Lack offish food because ofdependence on producer

Essay Question(a) The quantity of oxygen that is requrred by the microorganisms to deeompose the

organic substances in the water.(b) . Wastes/domestrc uaste matenal

e DecomposeC b,v decomposing bactenao Increase the usage oforygenr Flou, of hot u'ater from the factones increase the lvater temperatureo Decrease the solubility of orygen in ihe rvatero Florv of organic fertilisers from agricultural areaso Encourages algae growth. which prevents light from reactung the bottom of the lakeo Decrease the rate of photos.r,nthesis and decrease the rate of oxygen releaseo Aquatic animals die as a result of a lack of ox-_vgeno DecomFosition of dead animals (and plants) increases B.O D.o The effect of B.O.D. increase is the death/migration of aquatic animals

(c) 1 Replace cFC with easily biodegradable substances such as HCFC- reduce the thinning of the ozone la.v-er

2 Process the faciory/domestic rvaste products/filtered cilmneys- reduces water pollution that is caused by the decomposition of organic substances

3 Prepare a special disposal area for radioactive substances I metal- reduce environmental poliution that is caused b,-v raciioactive rays

4 Recycle substances such as glass/plastic lp ap er I aluminium- maintain natural resources

5 Use electric/soiar powered vehicles to reduce air poiiution that is caused byhydroearbon gases

6 Bum garbage in incinerators to reduce soil and air pollution.7 change oil paim remains into biogas to maintain naturar resourcesB Use biotechnology methods to clean up oil spills in order to control water pollution9 Design houses that save energy

- reduce the usage of substances tbr air-conditionersi0 Cloud seeding to reduce haze resulting from forest bumrng