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Answers to Continuous Evaluation
New Biology — a modern approach
15 Detecting environmental conditions
Class Practice
15.1 Irritability
1. C
2. D
3. A
4. B
5. E
6. F
15.2 The five senses
1. T
2. F
3. F
4. T
5. F
6. T
7. T
8. F
15.3 The eye
(a) A is eyebrow and B is eyelash.
Eyebrow prevents the sweat on the forehead from going into the eyes.
Eyelash helps to stop dirt from entering the eyes.
(b) Tears moisten eyeball surface.
Tears wash eyeball surface during blinking.
The fluid contains lysozome which kills bacteria. (any two)
15.4 Structure and functions of the eye
1. cornea/lens
2.
3.
4.
5.
6.
7.
8.
9.
10.
sclera/ aqueous humour and vitreous humour
retina
optic nerve
choroid
yellow spot
blind spot
suspensory ligaments
iris and pupil
visual purple
© Aristo Educational Press Ltd 2007
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New Biology — a modern approach
Answers to Continuous Evaluation
15.5 The control of the amount of light entering the eye
(a) smaller
(b) circular
(c) radial
(d) less
15.6 The accommodation of the eye
A. 1. (a) accommodation
2. (b) ciliary muscles
(c) suspensory ligaments
B.
(d) thicker
(e) retina
(a) Diagram I - long sight
Diagram II - short sight
(b)
Diagram I
Diagram II
Exam Practice
A. Multiple Choice
1. B
2.
3.
4.
5.
6.
7.
8.
9.
B
A
C
D
C
A
C
A
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Answers to Continuous Evaluation
B.
New Biology — a modern approach
Structured Questions
1. (a) P - rod cell
(b)
(c)
(d)
2.
(a)
3.
(b)
(c)
(d)
(e)
(f)
(a)
Q - cone cell
X - blind spot
Y - yellow spot
Cones are concentrated in the yellow spot.
Rods are abundant at the periphery of the retina.
Rod cells are more sensitive to lower light intensities when compared to cone cells.
Rod cells are more abundant at the edge of the retina. As a result, the peripheral
regions are more efficient in detecting object in dim light.
rods and cones
ciliary muscles
sclera
choroid
aqueous humour
vitreous humour
D becomes thicker. It is caused by the contraction of ciliary muscles (A). This
reduces the tension of suspensory ligaments.
(b) I can detect the form and colour of an object but J cannot. It is because I is
concentrated with cone cells which are responsible for colour vision but J does not
contain any light-sensitive cells.
(c) (i)
The eye defect is short sight. It may be due to the eyeball being too long or the
lens being too curved.
(ii) Short sight can be corrected by wearing concave lenses.
(d) (i) Cones are responsible for colour vision. However, cone cells require a higher
light intensity to function properly.
(ii) The visual purple in rods is responsible for night vision. However, visual
purple is broken down easily when it is in contact with light. This phenomenon
is called bleaching. After returning to the dark, it takes time for the visual
purple to be resysthesised.
C.
1.
STS Connections
(a) sclera
(b) Iris. There are circular muscles and radial muscles in iris. In bright light, circular muscles
contract and radial muscles relax to make the pupil constricts to reduce the amount of
light passing through.
(c) The retina has two types of light-sensitive cells (cones and rods) distributed unevenly on
different regions, while the film does not.
The retina is connected to the brain via optic nerve to produce vision, while the film is
not.
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Answers to Continuous Evaluation
2.
New Biology — a modern approach
(a) The lens of the patient becomes cloudy.
This will lead to a progressive loss of vision.
(b) by surgery
- cloudy lens is removed.
- plastic lens is replaced instead.
(c) - prevent long-period exposure to ultraviolet light
- have a balanced diet (prevention of diabetes by lowering sugar content in meals)
(Any one or other reasonable answers)
(d) Contents (3 marks)
Organization (1 marks)
(Focus on the social aspect of the problem.)
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