Q4
1 markVery Short AnswerSection A

Consider the following food chain which occurs in a forest: Grass → Deer → Lion. If 10000 J of solar energy is available to the grass, how much energy would be available to the deer to transfer it to the lion?

Our Environment
Food Chains and Webs
Official Answer

The energy available to the deer to transfer to the lion is 10 J10\text{ J}.

1% of solar energy10% law100 J10 J

Marking Scheme

  • 1Calculating energy captured by grass as 1%1\% of 10000 J=100 J10000\text{ J} = 100\text{ J}: [0.5 mark]
  • 2Calculating energy available in deer as 10% of 100 J=10 J10\% \text{ of } 100\text{ J} = 10\text{ J}: [0.5 mark]

Hint

First apply the 1%1\% rule for solar energy captured by plants, then apply the 10%10\% law for energy transfer from plants to the herbivore.

Quick Oral Answer

The grass captures 1%1\% of 10000 J10000\text{ J}, which is 100 J100\text{ J}. The deer gets 10%10\% of that, which is 10 J10\text{ J}. So, 10 J10\text{ J} is available in the deer to be transferred to the lion.

Analysis & Explanation

The first step involves the capture of solar energy by autotrophs, which is always around 1%1\% of the total solar energy incident on them. Subsequent transfers between trophic levels (from Grass to Deer) follow the 10%10\% law, where only 10%10\% of the energy of the previous level is stored and made available to the next level.

Common Mistakes

  1. 1Applying the 10%10\% law directly to the solar energy (getting 1000 J1000\text{ J} for grass), forgetting that plants only capture 1%1\% of solar energy.
  2. 2Confusing the energy available at the deer's level (10 J10\text{ J}) with the energy that the lion will actually assimilate (1 J1\text{ J}).

Interesting Facts

Because of the massive loss of energy at each step (about 90%90\% lost as heat, digestion, respiration, etc.), food chains rarely exceed 4 to 5 trophic levels.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2012?

This question carries 1 mark in the CBSE Class 10 Science 2012 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Our Environment" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Food Chains and Webs" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2012 paper?

This is a Very Short Answer question from Section A in the CBSE Class 10 Science 2012 paper.