Skip to content

Use the information… (Class 12 Biology SQP 2023-24, Q21b)

questionbuddy.in/q/cbse-12-biology-2023-24-sqp-q21b-use-information-provided-table-tropic

BiologyCBSE Class 12 · Sample paper, session 2023-24 · 2 marks · Very short answer

CBSE Class 12 Biology sample paper 2023-24: question 21(b)

From the official CBSE sample question paper for 2023-24, section B, question 21(b), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21(b) · 2 marks · Very short answerCompetency-basedEcosystem

Use the information provided in the table given below to answer the following questions:

Tropic levelNet Production (KJmy)Respiration (KJmy)
Top Carnivore5035
Carnivores420378
Herbivores44904041
Producers4500040,367

a) Calculate the gross primary productivity.
b) Analyze the trend in the Net Production from Producers to Top Carnivore. Give a reason for your observation.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2023-24.

Hints

Open one hint at a time and try again before the next.

Hint 1

Recall: GPP minus respiration loss equals NPP.

Hint 2

Look at how each level's net production compares with the level below it. Roughly what fraction is passed on?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. a) GPP = NPP + R =

    1 mark

  2. b) Net production falls steadily from producers (45000) to herbivores (4490), carnivores (420) and top carnivores (50). At each level only about 10% of the energy is passed on (10% law), because most energy is lost as heat in respiration.

    1 mark

Answer: a) GPP = 85367 kJ m⁻² y⁻¹. b) Net production decreases at each higher trophic level (about 10% transfer) due to respiratory heat loss.

Where the marks are

  • GPP = NPP + respiration = 85367 kJ m⁻² y⁻¹ (1 mark)
  • States the decreasing trend with reason: respiration/heat loss/10% law (1 mark)

Revise the chapter

  • Chapter: Ecosystem (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Ecosystem, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2023-24: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.