Question

Regarding assertion and reason, choose the right option
Assertion [A] - The earth is a closed system with respect to matter and open with respect to energy.
Reason [R] - Energy is not recycled in an ecosystem.

• A. Both A and R are true and R explains A
• B. Both A and R are true R does not explain A
• C. A is true and R is false
• D. Both A and R are false

Answer 1

The correct option is A Both A and R are true and R explains A

Energy exists in a number of forms; only some of it is being utilized by living organisms. In an ecosystem, energy is obtained almost entirely as sunlight and this is converted to chemical energy by plants which then enters the food chain. During chemical reactions in living organisms, some of it is lost in the form of heat to the surrounding environment and cannot be reused by living organisms. It is because this heat cannot be recycled, energy flow in ecosystems is unidirectional and thus earth is said to be an open system with respect to energy. Like energy, minerals or nutrients such as carbon, nitrogen and phosphorus exist in different forms as different compounds. However, these are continuously recycled and so repeatedly used by living organisms. Hence we say the earth is a closed system with respect to matter.