CSEC BIOLOGY · SECTION A · SECTION TEST

Section A Test: Living Organisms in the Environment

Twenty multiple-choice items and three structured questions covering classification, ecological study, feeding relationships, nutrient cycles, human impact and conservation.

Living Organisms in the Environment20 MCQ31 structured marks≈ 45 min
Before you start

How to take this test

  1. Take it after you have worked through the lessons below — it checks the whole section, not one lesson.
  2. Work under exam conditions: about 45 minutes, no notes. Every question here is new; none is repeated from the lessons.
  3. Part 1: answer every multiple-choice item, then check. Items you get wrong tell you which lesson to revisit.
  4. Part 2: write full answers, then reveal each mark scheme and self-mark strictly.
  5. Your test score (multiple choice 50% + structured 50%) counts towards your section and paper readiness.

Lessons covered: A1 Classifying Living Organisms, A2 Carrying Out an Ecological Study, A3 Ecological Terms and Abiotic Factors, A4 Food Chains, Food Webs and Energy Flow, A5 Decomposers and Special Relationships, A6 Nutrient Cycles and Recycling, A7 Human Impact, Pollution and Climate Change, A8 Conservation and Population Growth

Part 1 · Multiple choice

Multiple choice

20 items covering the whole section. Choose the best answer for each, then check.

A1 · SO A1.2

1. Which feature places an organism in Kingdom Fungi rather than Kingdom Plantae?

Answer: B. Fungi have chitin cell walls and cannot photosynthesise. Ferns also make spores, and all plants are multicellular with nuclei.
A1 · SO A1.2

2. An animal has six jointed legs, three body parts and two pairs of wings. To which class does it belong?

Answer: C. Six legs, three body parts (head, thorax, abdomen) and wings are features of insects.
A1 · SO A1.2

3. In the scientific name Anolis sagrei, the word Anolis is the name of the

Answer: B. The first word of a binomial name is the genus; the second identifies the species.
A2 · SO A2.1

4. Students want to estimate the number of ghost crabs on a beach. Which method is MOST suitable?

Answer: D. Crabs move about quickly, so a mobile-animal method such as capture–recapture is needed.
A2 · SO A2.1

5. In a capture–recapture study, 30 snails were marked. In the second sample of 40 snails, 6 were marked. What is the estimated population?

Answer: A. (30 × 40) ÷ 6 = 1200 ÷ 6 = 200.
A2 · SO A2.1

6. Why should quadrats be placed at random positions?

Answer: C. Random placement means the sample is not affected by the student choosing “interesting” spots.
A3 · SO A2.2

7. Which of the following is an abiotic factor?

Answer: A. Abiotic factors are non-living; predation, competition and disease involve living organisms.
A3 · SO A2.2

8. All the populations of different species living together in a pond make up a(n)

Answer: A. A community is all the living organisms; adding the abiotic environment gives an ecosystem.
A4 · SO A3.2

9. In the food chain grass → grasshopper → lizard → hawk, the lizard is the

Answer: D. The lizard eats a primary consumer (the grasshopper), so it is a secondary consumer.
A4 · SO A4.1

10. Grass in a field fixes 50 000 kJ of energy. If about 10% passes from one level to the next, how much energy reaches the lizard in the chain grass → grasshopper → lizard?

Answer: C. 50 000 → 5000 (grasshopper) → 500 kJ (lizard).
A4 · SO A4.1

11. Which ecological pyramid can NEVER be inverted?

Answer: A. Energy is lost at every level, so each level always has less than the one below it.
A5 · SO A3.7

12. Barnacles live attached to the skin of a whale. They get transport and food from the water; the whale is unaffected. This relationship is

Answer: D. One partner benefits and the other is unaffected (+/0): commensalism.
A5 · SO A3.6

13. The MAIN role of decomposers in an ecosystem is to

Answer: D. Decomposers break down dead matter and release minerals that plants can absorb again.
A6 · SO A5.1

14. Which process returns carbon locked in fossil fuels to the atmosphere?

Answer: C. Burning (combustion) of coal, oil and gas releases carbon dioxide.
A6 · SO A5.1

15. Bacteria that convert ammonium compounds into nitrates are called

Answer: B. Nitrifying bacteria (Nitrosomonas, Nitrobacter) convert ammonium → nitrite → nitrate.
A6 · SO A5.1

16. Waterlogged soil often has fewer nitrates because

Answer: B. Low oxygen favours denitrifying bacteria, which turn nitrates back into nitrogen gas.
A7 · SO A6.2

17. During eutrophication of a pond, fish die MAINLY because

Answer: D. Aerobic respiration by the large population of decomposing bacteria removes dissolved oxygen.
A7 · SO A6.3

18. Coral bleaching is MOST directly caused by

Answer: B. Warm water stresses corals, which expel the algae living in their tissues and turn white.
A8 · SO A7.1

19. In a population growth curve, the phase in which the birth rate equals the death rate is the

Answer: A. Numbers level off when births and deaths balance — the stationary phase.
A8 · SO A6.5

20. Which of these is an example of RESTORATION rather than conservation?

Answer: C. Restoration repairs a damaged habitat; the others protect what still exists.
Part 2 · Structured questions

Structured questions

3 Paper 2 style questions (31 marks). Write your answers first, then reveal the mark scheme and tick the points you earned.

A2 · Original · SO A2.1, A2.2, A3.2, A4.1

Question 1 [10 marks]

Students studied a transect running from the sea’s edge through a mangrove swamp to dry land.

Distance from sea (m)0102030
Salinity of soil water (parts per thousand)3525123
Number of red mangrove plants14610
Number of buttonwood plants02711

(a) Name the sampling method used by the students. [1]

MARK SCHEME — (a) (max 1)

(b) Describe how the number of red mangrove plants changes in relation to salinity. [2]

MARK SCHEME — (b) (max 2)

(c) Suggest why the results from a single transect may not be reliable. [2]

MARK SCHEME — (c) (max 2)

(d) Define the term “niche” and state ONE way it differs from “habitat”. [2]

MARK SCHEME — (d) (max 2)

(e) In the food chain mangrove leaves → crab → heron, identify the primary consumer and explain why less energy is available to the heron than to the crab. [3]

MARK SCHEME — (e) (max 3)

A6 · Original · SO A3.6, A3.7, A5.1

Question 2 [10 marks]

Pigeon peas are often grown by Caribbean farmers to improve the soil. Their roots have small swellings called nodules.

(a) Name the organisms found in the root nodules and the type of relationship they have with the pigeon pea. [2]

MARK SCHEME — (a) (max 2)

(b) Explain how EACH partner benefits. [2]

MARK SCHEME — (b) (max 2)

(c) Describe how the nitrogen in a dead plant can become available as nitrate to another plant. [3]

MARK SCHEME — (c) (max 3)

(d) Explain why farmers are advised to plough crop remains into the soil rather than burn them. [3]

MARK SCHEME — (d) (max 3)

A7 · Original · SO A6.2, A6.3, A6.5, A7.1

Question 3 [11 marks]

A large hotel discharges partly treated sewage into a bay that contains a coral reef.

(a) Explain TWO ways in which the sewage could damage the coral reef. [4]

MARK SCHEME — (a) (max 4)

(b) Suggest THREE measures the government could take to protect the reef. Explain each. [3]

MARK SCHEME — (b) (max 3)

(c) Distinguish between conservation and restoration, giving ONE example of each. [2]

MARK SCHEME — (c) (max 2)

(d) Explain why the human population of the world grew rapidly during the last 200 years. [2]

MARK SCHEME — (d) (max 2)

Your result

Test score

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