The eye

1 (a) Diagram 1 shows a section through an eye with parts labelled A to F.

Give the letter that labels the cornea.

Give the letter that labels a jelly-like fluid.

Give the function of part A.

Diagram 2 shows a section through the eye of a person with a detached retina.

Suggest how a detached retina could affect vision.

The diagram shows a section of a human eye.

Explain how part X prevents damage to the retina in very bright light.

Explain why damage to part Y would affect the ability to see.

In some people the lens in the eye becomes cloudy. A cloudy lens is called a cataract.

Explain how a cataract would affect the ability to see.

The population of the USA is 322 million, of which 47.0% are over 40 years of age. 17.2% of the people over the age of 40 develop a cataract. Calculate the number of people in the USA over the age of 40 who develop a cataract.

number of people =_........

Cataracts develop when proteins in the lens clump together. Lanosterol is a chemical that helps to break up these clumps of protein. In 2015, scientists investigated the ability of lanosterol to cure cataracts. They put drops of lanosterol solution into the eyes of rats with cataracts. After six days of treatment they counted the number of rats with a clear lens and the number of rats that still had cataracts. The graph shows the results.

One conclusion from this investigation is that lanosterol cures cataracts in humans.

Explain why some people might agree with this conclusion.

Give two reasons why some people do not agree with this conclusion.

The diagram shows a food web from a forest.

Use information from the food web to complete the table. The first one has been done for you.

Plant cell walls are made of cellulose. Cellulose is an insoluble molecule made from the same simple sugar as starch. The rabbit’s intestine contains bacteria that can digest cellulose. Suggest why this is an advantage for the rabbit.

The deer runs away when it sees the wolf.

Name the effector in this response.

The deer releases a hormone when it sees the wolf. Explain how this hormone helps the deer to run away.

The owl uses its eyes to find prey. The diagram shows a section through the owl’s eye.

Name the parts labelled A and B.

Describe the function of part A.

Describe the function of part B.

Name the producer in this food web.

Gazelles try to avoid being caught by lions by running away quickly. They can run at a top speed of 96 km per hour.

Calculate the distance in metres a gazelle runs in one minute at a speed of 96 km per hour. Show your working.

distance =_........ metres

Gazelles cannot maintain their top speed for a long time because a change in the type of respiration takes place in their muscle cells. Explain how this change in respiration stops gazelles from running at a top speed for a long time.

Zebras also try to avoid being caught by lions. It was thought that the striped coat of zebras helps to camouflage them. A new theory suggests the striped coat evolved because it reduces the number of biting flies that feed on zebra blood. Use your knowledge of natural selection to explain how a striped coat that reduces the number of flies feeding on zebra blood may have evolved.

Lions’ eyes are adapted to help them see in dim light.

Their eyes have a layer of cells behind the retina that reflects light which has passed through the retina. Suggest how this would help a lion see in low light intensities.

Suggest one other adaptation in the structure of a lion’s eye that helps the lion to see in low light intensities.

When a lion catches its prey it tears the meat into smaller pieces in its mouth before swallowing.

Suggest why the saliva released into the lion’s mouth does not contain amylase.

Explain how tearing the meat into smaller pieces helps digestion in the stomach.

The diagram shows a section through the human eye. Different parts of the eye have been labelled A to G.

The table lists some health problems that affect the eye and describes how they are caused. Complete the table by choosing the correct label letter for the part of the eye linked with each health problem. The first one has been done for you.

The diagram shows the difference in the pupil diameter of the eye in bright light and after moving into dim light. The difference is caused by a reflex action.

The table gives descriptions of parts of the reflex arc involved with the reflex action. Complete the table by naming each part. One has been done for you.

Explain how the lens changes when you view a near object.