Biogeochemical Cycles | Natural Resources | Assessment | English | Grade 9

Which of the following is not a part of water cycle?

• Photosynthesis

• Evaporation

• Condensation

• Precipitation

Answer explanation

Photosynthesis is not the part of water cycle. It is the process by which plants make their own food. Evaporation, condensation and precipitation are the steps involved in water cycle.

Complete the following sentence. Oxygen returns to the atmosphere ______.

• By burning fossil fuels

• By respiration

• By photosynthesis

• All of these

Answer explanation

By the process of photosynthesis, plants take in carbon dioxide and release oxygen in the atmosphere.

The percentage of oxygen in atmosphere is ____.

• 0.21

• 0.0004

• 0.78

• 0.0016

Answer explanation

Oxygen: 21% Carbon dioxide: 0.04% Nitrogen: 78% Other: 0.16%

Choose the correct option among the following.

• Atmospheric CO₂ → Organic carbon in plants → Organic carbon in animals →Inorganic carbon in soil

• Decomposers → Atmospheric CO₂ →Organic carbon in animals

• Atmospheric CO₂ → Decomposers → Organic carbon in animals →Organic carbon in plants

• Organic carbon in animals → Decomposers → Atmospheric CO₂ → Organic carbon in plants

Answer explanation

Atmospheric CO₂ is absorbed by the plants to carry out photosynthesis to form organic materials. When animals eat these plants, they intake these organic material. When plants and animals die these organic material gets converted to inorganic carbon by decomposers.

Which step is not involved in the carbon-cycle?

• Photosynthesis

• Evaporation

• Burning of coal

• Respiration of animals

Answer explanation

Evaporation is the conversion of water to water vapour. It is not involved in carbon cycle. Photosynthesis is used to convert carbon dioxide to food. Burning of coal releases carbon dioxide into atmosphere. Carbon dioxide is also released to atmosphere by respiration of animals.

Fill in the blank with respect to water cycle. The process in which water droplets, dust particles and other suspended particles combine to form clouds is called ______.

• Precipitation

• Condensation

• Assimilation

• Ammonification

Answer explanation

The process in which water droplets, dust particles and other suspended particle combines to form clouds is called condensation. In water cycle, when temperature is too low, precipitation occurs in form of snow or hail. Assimilation and ammonification are the processes of nitrogen cycle.

Select the correct statement among the following Statement 1: Carbon cycle is getting disturbed due to excess burning of fossil fuels. Statement 2: Carbon cycle is getting disturbed due to cutting of trees.

• Only statement 1

• Only statement 2

• Both statement 1 and statement 2

• Neither statement 1 nor statement 2

Answer explanation

In atmosphere carbon is present in the form of carbon dioxide. In carbon cycle, carbon from the atmosphere is taken and then released back in the atmosphere. But to due to human activities like burning of fossil fuels, excess of carbon dioxide is released in the atmosphere. Plants take in carbon dioxide, however for various purposes like construction and industrialisation, plants / trees are even cut down. Due to this the percentage of carbon in atmosphere is increased, thereby, disturbing carbon cycle.