Question 31 markVery Short AnswerSection A

In the following food chain, plants provide 500 J of energy to rats. How much energy will be available to hawks from snakes ?

Plants →\rightarrow Rats →\rightarrow Snakes →\rightarrow Hawks

Chemical Reactions and Equations
Energy Flow in Ecosystem

Official answer

The energy available to hawks from snakes will be 5 J5 \text{ J}.

Answer keywords:10%10\% Law50 J50 \text{ J}5 J5 \text{ J}trophic levelenergy transfer

Marking scheme

  1. 1.0.5 marks for calculating energy for snakes (50 J50 \text{ J})
  2. 2.0.5 marks for calculating energy for hawks (5 J5 \text{ J})

Hint

Apply the 10%10\% law for each step in the food chain: Rats →\rightarrow Snakes →\rightarrow Hawks.

Quick oral answer

Using the 10%10\% law, if rats have 500 J500 \text{ J}, snakes get 50 J50 \text{ J}, and hawks finally receive 5 J5 \text{ J}.

Common mistakes

  1. 1.Applying the 10%10\% law starting from the wrong level.
  2. 2.Calculating 10%10\% of the total plant energy instead of the energy provided to rats.
  3. 3.Incorrect decimal placement.

Analysis and explanation

The NCERT text (Section 1.2.1) notes that we need energy to stay alive and obtain it from food. In an ecosystem, this energy transfer follows the 10%10\% rule. As energy moves from rats to snakes and then to hawks, 90%90\% is lost (largely as heat during respiration, which is an exothermic process as per Eq. 1.18) and only 10%10\% is passed to the next level.

Interesting facts

Because energy decreases so rapidly at each level, food chains rarely exceed four or five trophic levels.

Question details

Q3 of 36 questions

Board
CBSE
Class
Class 10
Subject
Science
Year
2017
Section
Section A
Marks
1
Type
Very Short Answer
Chapter
Chemical Reactions and Equations
Topic
Energy Flow in Ecosystem
Bloom's level
Apply
Syllabus topic
Our Environment: Ecosystem - Energy flow

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Frequently asked questions

How many marks does this question carry in CBSE Class 10 Science 2017?

This question carries 1 mark in the CBSE Class 10 Science 2017 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Chemical Reactions and Equations" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Energy Flow in Ecosystem" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2017 paper?

This is a Very Short Answer question from Section A in the CBSE Class 10 Science 2017 paper.