BIOLOGY PAPER 2 2020 QUESTION AND ANSWERS GRADED A+
Suggest and explain how the interaction between the muscles labelled in Figure 1 could cause
the pupil to constrict (narrow).
-Circular muscle contracts
-Radial muscle relaxes
The fovea of the eye of an eagle has a high density of cones. An eagle focuses the image of its
prey onto the fovea. Explain how the fovea enables an eagle to see its prey in detail.
-Each cone is connected to a single neurone so there are separate impulses being carried to the
brain
so there is high visual acuity
The retina of the human eye has an area of approximately 1.094 × 103 mm2 The circular fovea
in a human eye has a diameter of 3 × 103 µm Calculate the area of the fovea as a percentage
of the area of the retina. The area of a circle is πr 2 . Use π = 3.14 in your calculation.
-0.6%
The retina of an owl has a high density of rod cells. Explain how this enables an owl to hunt its
prey at night.
-There are a lot of rods connected to a single neurone
and because of spatial summation the threshold can be met so there is high visual sensitivity
Name the two products of the light-dependent reaction that are required for the light-
independent reaction
ATP and Reduced NAD
Explain why steroid hormones can rapidly enter a cell by passing through its cell-surface
membrane.
-They can diffuse across the phospholipid bilayer
-They are lipid soluble
In the cytoplasm, testosterone binds to a specific androgen receptor (AR). An AR is a protein.
Suggest and explain why testosterone binds to a specific AR. [
-IT has a specific shape due to its tertiary structure that is complementary to the receptor
Describe the sequence of events involved in transmission across a cholinergic synapse
Suggest and explain how the interaction between the muscles labelled in Figure 1 could cause
the pupil to constrict (narrow).
-Circular muscle contracts
-Radial muscle relaxes
The fovea of the eye of an eagle has a high density of cones. An eagle focuses the image of its
prey onto the fovea. Explain how the fovea enables an eagle to see its prey in detail.
-Each cone is connected to a single neurone so there are separate impulses being carried to the
brain
so there is high visual acuity
The retina of the human eye has an area of approximately 1.094 × 103 mm2 The circular fovea
in a human eye has a diameter of 3 × 103 µm Calculate the area of the fovea as a percentage
of the area of the retina. The area of a circle is πr 2 . Use π = 3.14 in your calculation.
-0.6%
The retina of an owl has a high density of rod cells. Explain how this enables an owl to hunt its
prey at night.
-There are a lot of rods connected to a single neurone
and because of spatial summation the threshold can be met so there is high visual sensitivity
Name the two products of the light-dependent reaction that are required for the light-
independent reaction
ATP and Reduced NAD
Explain why steroid hormones can rapidly enter a cell by passing through its cell-surface
membrane.
-They can diffuse across the phospholipid bilayer
-They are lipid soluble
In the cytoplasm, testosterone binds to a specific androgen receptor (AR). An AR is a protein.
Suggest and explain why testosterone binds to a specific AR. [
-IT has a specific shape due to its tertiary structure that is complementary to the receptor
Describe the sequence of events involved in transmission across a cholinergic synapse
