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Air Around Us - Oxygen Cycle and Photosynthesis

Grade 6CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Photosynthesis is the process by which green plants use sunlight, water (H2OH_2O), and carbon dioxide (CO2CO_2) to prepare their own food (glucose) and release oxygen (O2O_2).

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The Oxygen Cycle is the natural process that maintains the level of oxygen in the atmosphere through photosynthesis and respiration.

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Respiration is the process where living organisms consume oxygen (O2O_2) to break down food for energy, releasing carbon dioxide (CO2CO_2) and water (H2OH_2O) as by-products.

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The balance of O2O_2 and CO2CO_2 in the atmosphere is primarily maintained by the interdependence of plants and animals.

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Plants are the primary producers of oxygen; during the day, the rate of photosynthesis is higher than the rate of respiration, resulting in a net release of O2O_2.

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Aquatic animals use dissolved oxygen (O2O_2) from water for respiration.

📐Formulae

6CO2+6H2O→Sunlight/ChlorophyllC6H12O6+6O26CO_2 + 6H_2O \xrightarrow{\text{Sunlight/Chlorophyll}} C_6H_{12}O_6 + 6O_2

C6H12O6+6O2→6CO2+6H2O+EnergyC_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}

Atmospheric Oxygen Concentration≈21%\text{Atmospheric Oxygen Concentration} \approx 21\%

💡Examples

Problem 1:

Explain how the balance of oxygen and carbon dioxide is maintained in the atmosphere.

Solution:

The balance is maintained through the Oxygen Cycle. Animals and plants consume O2O_2 and release CO2CO_2 during respiration. Conversely, plants consume CO2CO_2 and release O2O_2 during photosynthesis. This mutual exchange ensures the gases remain in equilibrium.

Explanation:

Since plants produce more O2O_2 during photosynthesis than they consume during respiration, they act as the main source of oxygen for the planet.

Problem 2:

Why is it advised not to sleep under a tree at night?

Solution:

At night, photosynthesis stops due to the absence of sunlight, but respiration continues. Therefore, trees take in O2O_2 and release CO2CO_2.

Explanation:

The accumulation of CO2CO_2 and the decrease of O2O_2 in the immediate vicinity of the tree at night can make breathing slightly more difficult for humans.

Problem 3:

What are the essential requirements for a plant to produce O2O_2?

Solution:

A plant requires Carbon dioxide (CO2CO_2), Water (H2OH_2O), Sunlight, and Chlorophyll.

Explanation:

Chlorophyll traps solar energy to convert CO2CO_2 and H2OH_2O into glucose (C6H12O6C_6H_{12}O_6), releasing O2O_2 as a vital byproduct.