15: Detecting the Environment - Problems Flashcards
(23 cards)
The photomicrograph below shows a parts of the longitudinal section of the wall of the human eyeball. Layer P is sensitive to light and layer Q contains many capillaries.
Identify cell X and support your answer with one observable feature from the photomicrograph. (2)
Cone cell,
because cell X is in cone shape.
The photomicrograph below shows a parts of the longitudinal section of the wall of the human eyeball. Layer P is sensitive to light and layer Q contains many capillaries.
Name layer Q and state two functions of it. (3)
Choroid
It contains a black pigment that absorbs light. This reduces reflection of light within the eye and thus helps form a sharp image on the retina.
It is rich in capillaries which supply nutrients and oxygen to the retina and sclera and remove wastes from them.
The photomicrograph below shows a parts of the longitudinal section of the wall of the human eyeball. Layer P is sensitive to light and layer Q contains many capillaries.
Explain why detachment of layer P from Q may result in vision loss. (2)
If layer P (retina) is detached from layer Q (choroid), some photoreceptors in the retina cannot obtain enough oxygen and nutrients from the capillaries in layer Q.
The photoreceptors die and can no longer generate nerve impulses when light falls on them. This results in vision loss.
The diagram below shows a section of the human eye.
Describe how the size of part Y changed when a person walks out from a dark room into bright light, and explain the importance of the change. (3)
When a person walks out from a dark room into bright light, the circular muscles of the iris contract and the radial muscles relax.
As a result, part Y (pupil) constricts.
This prevents the photoreceptors in the retina from being damaged by bright light.
Patients of presbyopia cannot focus clearly on near objects. Suggest why ageing of structure X may be a cause of presbyopia. (3)
Aged/weakened structure X (ciliary muscle) is not able to generate enough force for contraction when focusing on near objects.
The tension in the suspensory ligament remains at a point which is higher than the required tension.
Therefore, the lens cannot become thick enough to focus light rays from a near object onto the retina.
A boy was waiting for a bus at a bus stop. He saw a bus coming. The photographs below how what he saw when the bus was 15m away from the bus stop and at the bus stop.
Describe and explain the changes which occurred in the boy’s eyes when the bus approaches the bus stop. (3)
When the bus was approaching the bus stop, the degree of contraction of the ciliary muscles in the boy’s eyes increased.
The tension in the suspensory ligaments decreases and the suspensory ligaments become more and more slackened.
The lens becomes thicker and thicker in attempt to focus more and more light rays from the approaching bus onto the retina.
CE 2010 I Q5
Macular degeneration is a disease resulting in the loss of light-sensitive cells in the yellow spot of patients. The centre of vision of the patients is serious blurred.
Explain why the vision of the patient with macular degeneration is seriously blurred in the centre. (2)
The vision in the centre mainly relies on the the detection of light falling on the yellow spot.
As the yellow spot contains cone cells only, light falling on this spot can hardly be detected by patients with this disease. As a result, the vision becomes blurred in the centre.
CE 2010 I Q5
A pair of bionic eyes consists of a camera mounted on a pair of glasses worn by the patient. Signals from the camera are sent to a device implanted behind the retina of the eye of the patient.
Explain if the bionic eyes can be used to help patients without any light-sensitive cells in their retina. (2)
Yes. This is because the signals sent from the camera can stimulate the optic nerve directly.
Light-sensitive cells are not required for the stimulation of the optic nerve.
CE 2010 I Q5
Another type of bionic eye consists of a device implanted in the brain. After receiving signals, the device will directly stimulate the brain to generate vision.
Name the part of the brain where the device should be implanted. (1)
Visual centre in the sensory area of the cerebrum.
CE 2010 I Q5
Another type of bionic eye consists of a device implanted in the brain. After receiving signals, the device will directly stimulate the brain to generate vision.
Suggest on advantage of implanting the bionic eye in the brain over implanting it behind the retina. (1)
This type of bionic eye can give the sensation of vision to a patient with a damaged optic nerve or ruptured eyeball.
A student did an experiment to study the growth of plants. She kept a coleoptile in darkness for 24 hours and then exposed it to unilateral light for 24 hours. The diagram below shows the result.
State two advantages of using coleoptiles in the experiment. (2)
The response of coleoptiles to light is easy to observe.
Coleoptiles grow rapidly.
A student did an experiment to study the growth of plants. She kept a coleoptile in darkness for 24 hours and then exposed it to unilateral light for 24 hours. The diagram below shows the result.
Suggest why the coleoptile was first kept in darkness for 24 hours. (1)
In darkness, the coleoptile grew straight. This ensures any directional growth observed is caused by subsequent light exposure.
A student did an experiment to study the growth of plants. She kept a coleoptile in darkness for 24 hours and then exposed it to unilateral light for 24 hours. The diagram below shows the result.
Explain the response of the coleoptile shown in the diagram. (3)
Auxins are produced at the coleoptile tip.
Under unilateral light, auxins move from the illuminated side to the shaded side of the coleoptile.
The high auxin concentration on the shaded side promotes growth there. So, the coleoptile bends towards light.
A student did an experiment to study the growth of plants. She kept a coleoptile in darkness for 24 hours and then exposed it to unilateral light for 24 hours. The diagram below shows the result.
State the significance of such a response to the plant. (1)
This enables leaves to reach a position where they can obtain the maximum amount of light for photosynthesis.
A student decapitated some coleoptiles. The tips were placed on agar blocks under different situations as shown in diagram 1. After one day, he transferred the agar blocks to the decapitated coleoptiles in darkness. Diagram 2 shows the appearance of the coleoptiles after three days.
In set-up Y, a mica plate was inserted into the coleoptile and agar block. Explain the purpose of the mica plate. (1)
To prevent the lateral transport of auxins.
A student decapitated some coleoptiles. The tips were placed on agar blocks under different situations as shown in diagram 1. After one day, he transferred the agar blocks to the decapitated coleoptiles in darkness. Diagram 2 shows the appearance of the coleoptiles after three days.
Explain the difference between the results of set-ups X, Y, and Z. (5)
In set-up X, the coleoptile tip was exposed to uniform light. In set-up Y, the lateral transport of auxins was prevented by the mica plate though the coleoptile was exposed to unilateral light.
Under such conditions, the auxins in the coleoptile tips and hence the agar blocks in both set-ups were distributed evenly.
As a result, the illuminated side and the shaded side of the decapitated coleoptiles grew at the same rate and **no bending **occurred.
In set-up Z, the coleoptile tip was exposed to unilateral light. This caused auxins to move from the illuminated side of the tip to the shaded side. Thus the agar block on the right contained more auxins than that on the left.
As a result, under the action of auxins, the right side of the decapitated coleoptile grew more rapidly than the left side. The coleoptile bends to the left.
A student decapitated some coleoptiles. The tips were placed on agar blocks under different situations as shown in diagram 1. After one day, he transferred the agar blocks to the decapitated coleoptiles in darkness. Diagram 2 shows the appearance of the coleoptiles after three days.
The agar blocks were prepared using the same set-ups in diagram 1 and they were put to tip-removed roots.
State and explain the expected appearance of the root in set-up Z after it was kept in darkness for three days. (4)
The root bends towards the right.
Since the right side of the root receives more auxins than the left side,
and a high concentration of auxins inhibits root growth,
the right side of the root grows more slowly, causing the root to bend towards the right.
DSE 2013 IBQ7
Darwin conducted an experiment to investigate the phototropism of plants. The results after various treatments of coleoptiles are shown in the diagrams below.
From the results of the experiment, explain which part of the coleoptile is responsible for detected unilateral light. (3)
The tip is responsible for detecting unilateral light.
If it is removed or blocked from the stimulus, no bending growth movement occurs.
On the other hand, the bending growth response is still produced even if the lower part of the coleoptile is covered in soil.
DSE 2013 IBQ7
Darwin conducted an experiment to investigate the phototropism of plants. The results after various treatments of coleoptiles are shown in the diagrams below.
Explain why it is necessary to have set-up III in this experiment. (1)
To show that failure in producing response in set-up II is not due to the effect of injury or damage when the tip is removed.
DSE 2013 IBQ7
Darwin conducted an experiment to investigate the phototropism of plants. The results after various treatments of coleoptiles are shown in the diagrams below.
After that, Boysen-Jensen performed some other experiments to study the nature of signal transmission involved in phototropism.
State the conclusion which can be drawn from Boysen-Jensen’s experiment. (3)
Some substances are produced in the tip of the coleoptiles,
which can diffuse through the agar block to reach the lower part of the coleoptile,
and lead to bending growth at the lower part of the coleoptile.
DSE 2013 IBQ7
Darwin conducted an experiment to investigate the phototropism of plants. The results after various treatments of coleoptiles are shown in the diagrams below.
After that, Boysen-Jensen performed some other experiments to study the nature of signal transmission involved in phototropism.
State the conclusion which can be drawn from Boysen-Jensen’s experiment. (3)
Some substances are produced in the tip of the coleoptiles,
which can diffuse through the agar block to reach the lower part of the coleoptile,
and lead to bending growth at the lower part of the coleoptile.
The effect of auxin concentration on shoot and root growth is shown below.
Compare the effect of auxins on the growth of shoot tips and root tips at a concentration of 10-4ppm. (1)
An auxin concentration of 10-4 ppm stimulates the same extent of elongation of the shoot tips and root tips.
The effect of auxin concentration on shoot and root growth is shown below.
Compare the effect of auxins on the growth of shoot tips and root tips at a concentration of 103ppm. (1)
An auxin concentration of 103 ppm stimulates elongation of the shoot tips,
but has no significant effect on the elongation of root tips.
