Total marks: 100 · Duration: 2 hours 30 minutes
Instructions to candidates
- This paper consists of SIX questions in TWO sections. Answer ALL questions.
- Section A has a compulsory data analysis question and two structured questions. Write your answers in the spaces provided.
- Section B has three extended response questions. Write your answers in the spaces provided at the end of each question.
- Where appropriate, answers should be illustrated by diagrams.
- You may use a silent, non-programmable calculator.
- In the January 2027 sitting, Paper 02 is hybrid: you read the questions on screen and write your answers in an answer booklet.
Information
- The total mark for this paper is 100. Section A carries 55 marks and Section B carries 45 marks.
- The marks for each question and part question are shown in brackets.
- This paper covers the CSEC Biology syllabus: living organisms in the environment; life processes and disease; and continuity and variation. It does not repeat any question from Practice Paper A.
Paper
Section A — Data Analysis and Structured Questions (55 marks)
Question 1 — Data analysis: transpiration and wind speed (25 marks)
A student investigated the effect of wind speed on the rate of water uptake by a leafy shoot of hibiscus. She cut the shoot under water and fitted it into a bubble potometer. A small air bubble was let into the capillary tube, which has a radius of 0.5 mm. An electric fan was placed 1 m from the shoot and set to each of its six speed settings in turn (setting 0 = fan off). For each setting, she recorded how far the bubble moved in 5 minutes.
| Fan setting | 0 | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| Distance moved by bubble in 5 minutes (mm) | 12 | 20 | 27 | 33 | 36 | 37 |
(a) (i) Calculate the rate of bubble movement, in mm per minute, for each fan setting. [2 marks]
(ii) Plot a line graph of rate of bubble movement against fan setting. [5 marks]
(iii) Describe the trend shown by your graph. [2 marks]
(iv) Suggest why the rate increases only a little between settings 4 and 5. [2 marks]
(b) (i) Identify the independent variable and the dependent variable in this investigation. [2 marks]
(ii) State two variables that the student should keep constant. [2 marks]
(iii) Explain why the shoot was cut under water and fitted into the potometer under water. [2 marks]
(c) A potometer measures the rate of water uptake, not the rate of transpiration. Explain why the two rates are not exactly the same. [2 marks]
(d) Calculate the volume of water taken up in 5 minutes at fan setting 5. Use volume = πr²l and take π as 3.14. Show your working. [2 marks]
(e) Outline how the student could use the same apparatus to investigate the effect of humidity on the rate of water uptake. [2 marks]
(f) Seagrape plants grow on dry, windy Caribbean beaches. Suggest two features of their leaves that reduce water loss. [2 marks]
Question 2 — Excretion and the kidney (15 marks)
The table shows the concentration of three substances in the blood plasma entering a kidney, in the filtrate in the Bowman's capsule, and in the urine of a healthy person.
| Substance | Blood plasma (g per 100 cm³) | Filtrate (g per 100 cm³) | Urine (g per 100 cm³) |
|---|---|---|---|
| Protein | 8.0 | 0 | 0 |
| Glucose | 0.1 | 0.1 | 0 |
| Urea | 0.03 | 0.03 | 2.0 |
(a) Name the part of the nephron where blood is filtered under high pressure. [1 mark]
(b) Explain why there is no protein in the filtrate. [2 marks]
(c) Explain why glucose is present in the filtrate but not in the urine. [2 marks]
(d) Calculate how many times more concentrated urea is in the urine than in the filtrate. [2 marks]
(e) A farmer works in the sun all day and drinks very little. Explain how ADH changes the volume and concentration of his urine. [3 marks]
(f) Distinguish between excretion and egestion. [2 marks]
(g) State two treatments for kidney failure, and give one advantage of one of them over the other. [3 marks]
Question 3 — Reproduction and inheritance (15 marks)
(a) Distinguish between pollination and fertilisation in flowering plants. [3 marks]
(b) State two ways in which a wind-pollinated flower differs from an insect-pollinated flower. [2 marks]
(c) In pigeon peas, purple flower colour (P) is dominant to white flower colour (p). A plant heterozygous for flower colour is crossed with a white-flowered plant.
(i) Draw a genetic diagram to show the genotypes and phenotypes of the offspring. [3 marks]
(ii) State the expected ratio of purple-flowered to white-flowered offspring. [1 mark]
(d) Seeds from the same pigeon pea pod grow into plants that are not all identical. Explain two causes of this variation. [2 marks]
(e) Name two hormones that control the menstrual cycle, and state one role of each. [2 marks]
(f) Name one method of contraception and explain how it prevents pregnancy. [2 marks]
Section B — Extended Response (45 marks)
Question 4 — Ecology and human impact: mangroves (15 marks)
(a) Describe how a line transect could be used to study how plant species change from the sea's edge to dry land in a mangrove swamp. [4 marks]
(b) Explain three ways in which mangroves are important to Caribbean coastal ecosystems. [3 marks]
(c) A developer clears a mangrove swamp to build a hotel. Explain how this is likely to affect local fish catches and the coastline. [4 marks]
(d) Plastic waste is a growing problem on Caribbean coasts. Explain two ways in which plastic harms marine animals, and suggest one way of reducing it. [4 marks]
Question 5 — Coordination and control (15 marks)
(a) Give three differences between nervous control and hormonal control in humans. [3 marks]
(b) A boy touches a hot pot and pulls his hand away before he feels the pain. Describe how this reflex action happens. [5 marks]
(c) Explain how the eye changes so that a student can focus on a book after looking at a distant tree. [4 marks]
(d) Explain how the blood glucose concentration returns to normal after a meal rich in starch. [3 marks]
Question 6 — Transport and support (15 marks)
(a) Describe the route taken by blood from the lungs to the body tissues, naming the chambers of the heart and the blood vessels it passes through. [5 marks]
(b) Explain how water moves from the soil to the leaves of a tall tree. [5 marks]
(c) Explain how the structures of the elbow joint work together to allow the arm to bend and straighten smoothly. [5 marks]