Life on Earth - Chapter 15 Class 11 NCERT Geography

1. Multiple choice questions. 

(i) Which one of the following is included in biosphere?

(a) only plants

(b) all living and  non-living organisms

(c) only animals  

(d) all living organisms

(ii) Tropical grasslands are also known as :

(a)    the prairies

(b) the savannas

(c) the steppes

(d) none of the above

(iii) Oxygen combines with iron found in the rocks to form :

(a)    iron carbonate

(b) iron nitrites

(c) iron oxides

(d) iron sulphate

(iv) During photosynthesis, carbon dioxide combines with water in the presence of sunlight to form : (a) proteins

(b) amino acids

(c) carbohydrates

(d) vitamins

2. Answer the following questions in about 30 words.

(i) What do you understand by the term ‘ecology’?

Ans. The term ecology is derived from the Greek word ‘oikos’ meaning ‘house’, combined with the word ‘logy’ meaning the ‘science of’ or ‘the study of’. Ecology is the study of the earth as a ‘household’, of plants, human beings, animals and micro-organisms.

(ii) What is an ecological system? Identify the major types of ecosystems in the world.

Ans. The interactions of a particular group of organisms with abiotic factors within a particular habitat resulting in clearly defined energy flows and material cycles on land, water and air, are called ecological systems.

The two major types of ecosystem are - terrestrial and aquatic

(iii) What is a food-chain? Give one example of a grazing food-chain identifying the various levels.

Ans. This sequence of eating and being eaten and the resultant transfer of energy from one level to another is known as the food-chain. For e.g. – Plants (producers) get eaten by rabbits, deer, cow etc...(herbivores animals), similarly herbivores animals get eaten by fox, lion, tiger, eagle etc...(carnivores animals).

(iv) What do you understand by the term ‘food web’? Give examples.

Ans. A food web is a natural interconnection of food chains. In other words, a network of food chains mixed together to form food web.

(v) What is a biome?

Ans. A biome is a plant and animal community that covers a large geographical area. This geographical area is usually determined by climate.

3. Answer the following questions in about 150 words.

(i) What are bio-geochemical cycles? Explain how nitrogen is fixed in the atmosphere.

Ans. Bio-geochemical cycles are chemical exchange between living organisms that is where the term “bio” come from, and the “geographic” element of the earth such as - rocks, soil, air, and water. In simple terms, it is a cycle that shows the movement of chemical elements between the biotic (living organism) and the abiotic (non-living organism) components of the environment.

Nitrogen is a major constituent of the atmosphere comprising about 79% of the atmospheric gases. Nitrogen is considered as an unreactive gas. Nitrogen gas is formed when two nitrogen atoms bond together. Nitrogen molecules have a triple covalent bond and it requires a huge amount of energy to break triple bonds. Hence, this massive energy can be obtained by lightning and cosmic radiation.

(ii) What is an ecological balance? Discuss the important measures needed to prevent ecological imbalances.

Ans. Ecological balance is a state where there is equality between organisms and their environment in terms of coexistence.

Ecological imbalance occurs due to the introduction of new species, natural hazards or human causes.

Measures to prevent ecological imbalance:-

1. Manage Natural Resources Carefully

2. Controlling Population - reducing human consumption of natural resources

3. Protecting the Water

4. Recycling

5. Planting more trees

6. Improving farming techniques to avoid land degradation

7. Shifting from Fossil Fuels to Sustainable Energy