Question

By observing the interdependence of plants and animals and circulation of oxygen and carbon dioxide we can say that
A) Someday all the oxygen will be used up by the animals
B) Someday all the carbon dioxide will be used up by the plants
C) The amount of oxygen is increasing and that of carbon dioxide is decreasing in our atmosphere.
D) The level of oxygen and carbon dioxide in the atmosphere is kept constant.

Answer 1

Plants and animals are interdependent on each other due to the circulation of oxygen and carbon dioxide because plants release oxygen and consume carbon dioxide during photosynthesis and animals consume oxygen and release carbon dioxide during respiration.

Complete answer:
By observing the interdependence of plants and animals and the circulation of oxygen and carbon dioxide we can say that the level of oxygen and carbon dioxide in the atmosphere is kept constant because of a dynamic equilibrium established between these gases and plants and animals.

Oxygen is released by plants during photosynthesis when the splitting of water occurs to release hydrogen ions and free oxygen. And carbon dioxide is utilized for carbon fixation and makes organic compounds like glucose. Animals utilize oxygen as the final electron acceptor in the electron transport system (ETS) of respiration to produce water. Carbon dioxide is released by animals during the oxidation of food like glucose for the release of energy.

Additional information:
Plants and animals live together in an ecosystem and thus are interdependent on each other for various other reasons as well.

Animals are dependent on plants for their food as plants are the producers in an ecosystem and provide energy to all other organisms. This dependence is known as a food chain in which energy in a unidirectional manner from one organism to another. Normally multiple food chains are present in an ecosystem and are known as a food web.

Once animals are dead, they are decomposed and the nutrients seep into the soil which is then absorbed by the plants for growth and development. Thus, plants are dependent on animals in this way.
Other than this food dependence, plants and animals are also dependent on each other for reproduction. Plants depend on animals to carry out pollination and it is known as zoophily. In return animals like bees get nectar and some species like the Yucca moth get shelter to lay its eggs.

So, the correct answer is option ‘D’ i.e, ‘The level of oxygen and carbon dioxide in the atmosphere is kept constant.’

Note:
-Oxygen was first released into the atmosphere by blue-green algae i.e. cyanobacteria which produced oxygen by the splitting of water.
-Plants also perform respiration as they are aerobic organisms that derive energy by the breakdown of organic food. Therefore, plants also release carbon dioxide as a result of respiration, but most of it is consumed for the process of photosynthesis.
-The greenhouse effect is the heating of the planet due to the trapping of the sun’s energy due to the gases present in the Earth’s atmosphere.