CSEC Biology Paper 3 May/June 2012 - Free CXC Past Paper with Answers

(h)

Seedlings of the two species, labelled A and B, were carefully removed from the forest and each put into a pot containing soil from the same area. The plants were watered equally and exposed to the same light intensity. The length of the stem of each seedling was measured daily for two weeks and the results recorded in Table 1.

Plot the data in Table 1 on the grid provided on page 7.

TABLE 1: LENGTH OF STEM OF SEEDLINGS

Time (day)	Length of Stem (cm)
	Species A
1	3.0
2	3.4
4	4.3
8	11.0
10	13.5
12	15.6
13	16.0
14	15.8

[5 marks]

Question 2 (19 marks)

Some students in a biology class worked in pairs to investigate the reflex action shown in Figure 3.

Figure 3. Diagrammatic representation of a reflex action

(a)

Explain the usefulness of the reflex action shown in Figure 3.

[2 marks]

(b)

A footballer's kneecap (patella) is injured during a match. Explain how this injury may affect his knee jerk reflex.

[2 marks]

(c)

A researcher conducts an investigation to test the following hypothesis: "Alcohol consumption interferes with the transmission of nerve impulses in a reflex arc."

Describe how the procedure in Figure 3 could be used to test the hypothesis.

[4 marks]

(d)

Light of different intensities is shone into the eyes of a person and the changes in diameter of the pupil are illustrated in Figure 4.

Figure 4. Effect of different light intensities on the pupil of the eye

(d)(i)

Measure the diameter of the pupil of the eye shown in Figure 4 and record your results in Table 2.

TABLE 2: EFFECT OF LIGHT INTENSITY ON THE PUPIL OF THE EYE

Light Intensity (lux)	Diameter of the Pupil (mm)
50
100
200
300

[3 marks]

(d)(ii)

Write a suitable aim for this investigation.

[2 marks]

(d)(iii)

Describe ONE limitation of this investigation.

[1 mark]

(d)(iv)

Use the data in Table 2 to write a suitable conclusion for this experiment.

[2 marks]

(e)

Identify the part of the eye responsible for controlling pupil size and explain how it works.

[3 marks]

Question 3 (8 marks)

The effect of exercise on breathing rate in a group of 100 healthy male athletes was measured by researchers at a sport facility.

The data collected is shown in Table 3.

TABLE 3: EFFECT OF EXERCISE ON BREATHING RATE

Time After Exercise (minutes)	Average Number of Breaths per 15 seconds
1	6
3	5
5	4
7	3
9	2
11	2

(a)

Calculate the average number of breaths per minute in the first minute after exercise.

[1 mark]

(b)

On the grid provided on page 13, draw a graph to show the relationship between time and the average number of breaths per minute.

[5 marks]

(c)

Explain the shape of the graph.

[2 marks]

CSEC Biology Paper 3 May/June 2012 Questions

Question 1 (25 marks)

TABLE 1: LENGTH OF STEM OF SEEDLINGS

Question 2 (19 marks)

Question 3 (8 marks)