With reference to the sources of water vapour in the atmosphere, consider the following statements: 1. Water vapour is added to the air exclusively by the evaporation of water from oceans and lakes. 2. Evaporation from water bodies is a major source of water vapour in the air. 3. Transpiration by plants does not contribute to the water vapour in the air. Which of the statements given above is/are correct?

The correct option is (b). Explanation Water vapour is a variable gas in the atmosphere that plays a crucial role in weather phenomena and the Earth's energy budget. It enters the atmosphere through the hydrological cycle, which involves both physical processes (evaporation, sublimation) and biological processes (transpiration). Statement-wise Analysis: - Statement 1 is Incorrect: Water vapour is not added exclusively by evaporation from water bodies. While evaporation is the primary mechanism, other sources such as transpiration from plants, sublimation from ice caps and glaciers, and volcanic eruptions also contribute moisture to the air. - Statement 2 is Correct: Evaporation from oceans, seas, lakes, and rivers is the most significant source of atmospheric water vapour. Since oceans cover approximately 71% of the Earth's surface, they provide the vast majority of moisture to the atmosphere. - Statement 3 is Incorrect: Transpiration is the process through which plants release water vapour into the atmosphere, primarily through stomata in their leaves. This biological process is a major component of the water cycle (often collectively referred to with evaporation as evapotranspiration) and contributes significantly to atmospheric humidity. Key Takeaway: Atmospheric water vapour is replenished through evapotranspiration, which includes both evaporation from water bodies and soil, and transpiration from vegetation. It is not limited to evaporation alone.

With reference to the sources of water vapour in t... - NCERT Class 6 Environment & Ecology MCQ

Solution

The correct option is (b).

Explanation

Water vapour is a variable gas in the atmosphere that plays a crucial role in weather phenomena and the Earth's energy budget. It enters the atmosphere through the hydrological cycle, which involves both physical processes (evaporation, sublimation) and biological processes (transpiration).

Statement-wise Analysis:

Statement 1 is Incorrect: Water vapour is not added exclusively by evaporation from water bodies. While evaporation is the primary mechanism, other sources such as transpiration from plants, sublimation from ice caps and glaciers, and volcanic eruptions also contribute moisture to the air.
Statement 2 is Correct: Evaporation from oceans, seas, lakes, and rivers is the most significant source of atmospheric water vapour. Since oceans cover approximately 71% of the Earth's surface, they provide the vast majority of moisture to the atmosphere.
Statement 3 is Incorrect: Transpiration is the process through which plants release water vapour into the atmosphere, primarily through stomata in their leaves. This biological process is a major component of the water cycle (often collectively referred to with evaporation as evapotranspiration) and contributes significantly to atmospheric humidity.

Key Takeaway: Atmospheric water vapour is replenished through evapotranspiration, which includes both evaporation from water bodies and soil, and transpiration from vegetation. It is not limited to evaporation alone.

NCERT Class 6 Environment & Ecology — Chapter 1: Water

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