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Chapter 6

1 (a) (i) Pancreas (ii) Lipase (iii) Duodenum

(b) (i) Liver

(ii) Liver secretes bile which is transported from gall bladder to the duodenum.

Bile emulsify the fats into smaller droplets. This provides a larger surface for

digestion by lipase.

(c) Orange juice is mild acidic juice. Pancreatic amylase digest starch to maltose inalkaline medium in the duodenum. The mild acidic orange juice slows down the

digestion of starch.

(d) (i) Green papaya strips contains enzyme papain which hydrolyses proteins in

mutton into peptones. Thus tenderize the meat and reduce cooking time.

(ii) Enzyme has optimum temperature at 35 0C. Papain works effectively at 35 0C.

Chapter 8

Section A:

1. (a) (i) X: Mutualism Y: Commensalism

(ii) Rhizobium sp. live inside the root nodules of legumes plants. It converts

atmospheric nitrogen into ammonium compounds that are used by plants. Theplants provide the bacteria with organic compounds.

(b) (i) P: epiphyte Q:Saprophyte

(ii) Epiphytes are able to synthesise its own food. These plants grow on the trunks

of trees to obtain sunlight for photosynthesis.

(c) P is able to live if tree is tall enough for P to obtain enough sunlight.

(d) The hyphae of mushrooms secrete digestive enzymes to digest the organic

compounds on sawdust before absorbing the digested nutrients.

Section B:

1 (a) (i)

(ii)

(iii) Biological control is the method to control the population of rats. Owls areused to kill the rats. This method is better because less pesticide are used.

Harmless organisms are not killed together with pests. The effect of pesticides

is long-term and they remain in the environment for long periods. High

owl

snake

rat

Maize plant

Maize plant

Caterpillar

Grasshopper

Rat

frog

snake

owl

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concentrations of pesticides accumulate in the tissues of consumers. These

pesticides are toxic. The use of pesticides pollutes the environment.

(b) Colonisation is the process in which spores and seeds of plants start to germinate

and grow in a piece of barren land where air, water, nutrients and sunlight are

available.

Succession is a gradual process in which pioneer species changes the environmentso that it replaced by another successor.

Colonisation of an abandoned pond begins with the growth of submerged plants

such as Hydrilla sp. as pioneer species. When the pioneer species die and

decompose, the organic nutrients are released and the organic matter is converted

into humus at the pond base.

This makes the pond shallower and the conditions become more suitable for

floating plants.

These plants covered the water surface and prevent sunlight from reaching the

submerged plants. As a result, submerged plants die.

The decomposed remains of the plants and erosion at the edge results in more

sediments deposited at the base of the pond.The pond becomes shallower. The floating plants are replaced by emergent plants.

As the pond become shallower, these plants grow from the edge of the pond

towards the middle of the pond.

When the plants die, their decomposed remains add to the sediments at the base of

the pond. This reduces the depth of pond further.

This becomes more favourable for land plants as the land become drier.

A primary forest emerges and become tropical rain forest.

Chapter 9

1 (a) (i) Accidental or intentional release of petroleum/ oil products into the

environment.(ii) Illegal release of petroleum products from the ships into the seas

Oil contaminated runoff from refineries.

(iii) Oil destroys the insulating ability of birds and furbearing mammals sea

birds and animals ingest the oil during feeding or when they try to clean

themselves the animals are injured or killed.

(iv)Spray chemical detergents to break down oils Hot water is sprayed into

shoreline to wash off the oil. Transgenic bacteria may be sprayed to break

down thin film of oil.

(b) (i) Amount of oxygen used by aerobic microorganisms to break down organic

matter in a water sample.

(ii) The higher the BOD value, the higher degree of pollution and the number of

fauna species decreases.

(iii) Use a net to trap the solid untreated sewage particles before discharged

into the water. Strict enforcement of anti-pollution laws.

2 (a) There are fewer different types of lichens growing near the station. Coal-fired

power station produces sulphur dioxide from burning of biofuel. Lichens are

sensitive to atmospheric air polluted with sulphur dioxide. The growth rate of is

low in areas nearer to power station because of the high levels of sulphur dioxide.

There are more different types of lichen growing on the tree trucks further away

from the station because there is less air pollution.

(b) Sulphur dioxide dissolves in rain water to form acid rain. Acid rain decreases soilpH. Some plants cannot grow in acidic soils.

Acid rain corrodes the walls of building, damages iron bridges and fences.

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Sulphur dioxide diffuses through the stomata into the leaves, damages the

chlorophyll cells, thus killing the plants.

Sulphur dioxide irritates the lining of the eyes, damages the lining of respiratory

tubes and alveoli causing respiratory diseases.

(c) Carbon dioxide greenhouse effect

Nitrogen oxides acid rain