Biology test answer
1.
a
Carbon dioxide
1m
b
Overall increase in air temperature
1m
c
Ice in the polar regions may melt.
1m
The water level of the oceans will rise and the coastal area may sink below the sea
d
level.
1m
Deforestation causes the balance of carbon dioxide unable to maintain.
1m
Carbon dioxide produced from respiration of all organisms is more than that
absorbed by plants for photosynthesis. Therefore, the level of carbon dioxide in the
e
atmosphere rises.
1m
Sulphur dioxide and nitrogen dioxide
1m
When these gases are dissolved in rain, acid rain results.
1m
Trees and marine organisms are killed because the rain makes soil and water
acidic.
1m
Acid rain is corrosive and erodes metals, stones and other building materials.
1m
2.
a
Sewage discharged from the town and farm contains a lot of nutrients which can be
used by bacteria for growth.
b
c
1m
A lot of oxygen in the river is used up by the bacteria for growth and decomposition
of organic matters.
1m
The fish die of suffocation.
1m
The bacteria also release toxins which poison the fish.
1m
The discharged sewage contains a lot of nutrients for the growth of algae.
1m
The large population of algae prevents sunlight from passing through the water.
This reduces the photosynthetic rate of aquatic plants.
1m
The large population of algae prevents diffusion of oxygen into the water. The fish
die of suffocation.
1m
The algae block the gills of the fish. The fish die of suffocation.
1m
F.5
Biology test
p.2
When the algae die, they are decomposed by the bacteria, which use up oxygen in
the river. The fish die of suffocation.
d
1m
Setting up of a sewage treatment plant to make the sewage less harmful before it is
discharged.
1m
a
To let the solid part of the sewage / sludge settle down to the bottom.
1m
b
To stir up the sewage.
1m
To make the bacteria and fungi active
1m
in decomposing organic substances in the sewage
1m
into harmless inorganic compounds.
1m
Anaerobic bacteria carry out fermentation of the sludge in the digester.
1m
3.
c
Methane gas
As fuel to power the sewage treatment plant.
Sludge
d
0.5m
1m
0.5m
As plant fertilizers in farming.
1m
Mineral
1m
4.
a
b
The object is getting nearer and so the lens (K) becomes more convex to focus the
object on the retina.
1m
The ciliary muscles (I) contract.
1m
Tension in suspensory ligament (O) then reduces to make the lens more convex. 1m
Light is refracted more by the lens
1m
The circular muscles of the iris (N) contract and
1m
makes the pupil (M) smaller in size.
1m
Less light can enter the eye to prevent the retina from damage by bright light.
1m
F
1m
Yellow spot
1m
There is the highest concentration of cones
1m
5.
a
Short sight
Wear glasses of concave lens
1m
1m
F.5
Biology test
p.3
concave lens
sharp image is
formed on the
retina
3m
6.
a
b
Stimulus
---- sound
1m
Receptor
---- sound receptors in the ear
2m
Nerve impulses generated from sound receptors in the ear travel to the hearing
centre of the brain.
1m
The nerve impulses are processed and appropriate signals are sent to the motor
centre of the brain.
1m
Nerve impulses then travel from the motor centre to appropriate skeletal muscles to
c
d
start the running.
1m
This is not a reflex action because
1m
it involves the cerebrum of the brain and
1m
the reaction is learnt.
1m
Cerebellum
1m