NCERT 7th Class (CBSE) Social Science: Our Environment

Question: How have human needs undergone changes with the passage of time and technological development?

Answer: Early humans adjusted themselves with the surrounding in which they lived. Most of their needs were fulfilled from the environmental resources. Thus with time, the quality and quantity of human needs changed and they started developing techniques and new ways to use the environment. Humans settled in the fertile plains of the river valleys to cultivate land. They domesticated animals and learnt to use fire and invented wheel and it let to surplus food production and exchange of surplus goods.

Question: What is the importance of ecosystem?

Answer: The importance of an ecosystem is that it provides space to plants and animals to interact with each other as well as their physical environment. Through interactions they are interdependent on each other for their environment.

Question: The earth would have been a barren planet without the atmosphere do you agree? Why?

Answer: Yes, earth would have been a barren planet without the atmosphere because atmosphere is required for survival otherwise plants, animals and human beings will die.

Question: Why do plants and animals depend on each other?

Answer: Plants and animals depend on each other because plants need carbon dioxide which is given by animals and animals need food and oxygen which is given by planets.

Question: Describe the main features of natural and human made environment.

Answer: The natural elements, such as mountains, rivers, vegetation, animals etc. are created by nature. This is called natural environment. It includes the biotic and abiotic components. The human-made elements, such as agriculture, industries, settlements, means of transportation etc. are created by human beings. Therefore, it is called human-made environment. Human being develop features to live comfortably in their environment.

Question: Distinguish between biotic and abiotic environment with examples.

Answer: Following are the differences:

Question: Give an account of atmosphere.

Answer: Atmosphere is the thin layer of air that surrounds the earth. It is made up of various gases such as oxygen, nitrogen, carbon dioxide, dust particles and water vapour. The gravitational force of the earth holds the atmosphere around it. It protects us from harmful rays and scorching heat of the sun. The changes in atmosphere produce changes in the weather and climate.