Detailed, Step-by-Step NCERT Solutions for Class 11 Geography Chapter 15 Life on the Earth Questions and Answers were solved by Expert Teachers as per NCERT (CBSE) Book guidelines covering each topic in chapter to ensure complete preparation.
Life on the Earth NCERT Solutions for Class 11 Geography Chapter 15
Life on the Earth Questions and Answers Class 11 Geography Chapter 15
Question 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
Answer:
(b) all living and non-living organisms.
(ii) Tropical grasslands are also known as ……………..
(a) the prairies
(b) the savannas
(c) the steppes
(d) none of the above
Answer:
(b) the savannas.
(iii) Oxygen combines with iron found in the rocks to form
(a) iron carbonate
(b) iron nitrites
(c) iron oxides
(d) iron sulphate
Answer:
(c) iron oxides.
(iv) During photosynthesis, carbon dioxide combines with water in the presence of sunlight to form
(a) protein
(b) amino acids
(c) carbohydrates
(d) vitamins
Answer:
(c) carbohydrates.
Question 2.
Answer the following questions in about 30 words each :
(i) What do you understand by the term ‘ecology’?
Answer:
Ecology is the study of the earth as a ‘household’ of plants, animals and micro-organisms. They all live together as interdependent components.
(ii) What is an ecological system? Identify the major types of ecosystems in the world.
Answer:
The interactions of a particular group of organisms with land, air and water (abiotic factors) within a particular habitat or habitats, resulting in clearly defined energy flows and material cycles on land, water, and air, are called ecological systems.
Ecosystems are of two major types – terrestrial and aquatic. Terrestrial ecosystem is further classified into biornes. The major biomes of the world are – forest, grassland, desert and tundra biornes.
Aquatic ecosytem can be classified as marine and freshwater ecosystems. Marine ecosystem includes oceans, coastal estuaries and coral reefs. Freshwater ecosystem includes lakes, ponds, streams, marshes and bogs.
(iii) What is a food chain? Give one example of a grazing food- chain identifying the various levels.
Answer:
The food relation representing a producer, a primary consumer, a secondary consumer and a decomposer is called a food chain. The four trophic levels of a food chain are the producers, the herbivores or the primary or first order consumers (e,g. cattle, deer and goat), the carnivores or the secondary or second order consumers (e.g. lion) and the decomposers (e.g bacteria).
(iv) What do you understand by the term ‘food web’? Give examples.
Answer:
Many simple food chains intermingle with each other to form a food web. For example, each organism may eat a variety of food derived from another organism and, in turn, may be eaten by’a number of organisms at a higher level of the food chain. The primary producers use the energy of the sun and provide it to consumers at higher level. But energy is lost during each upward step in the food chain.
(e) What is a biome?
Answer:
The largest natural regions which occur in distinct group „ communities, in areas having similar climatic conditions, are known as biomes.
The major biomes of the world are :
- Tropical rain forest
- Tropical savanna
- Mediterranean scrub forest
- Deciduous forest
- Grassland
- Desert
- Taiga
- Tundra
Question 3.
Answer the following questions in about 150 words each :
(i) What are bio-geochemical cycles? Explain how nitrogen is fixed in the atmosphere.
Answer:
Living organisms survive with the flows of energy, water and nutrients. The balance between chemical elements of atmosphere and hydrosphere is maintained by a cyclic passage through the tissues of plants and animals. The cycle starts by absorbing of the chemical . elements by the organism and returned back to air, water and soil through decomposition. These cycles are largely energized by solar insolation.
These cyclic movements of chemical elements of the biosphere between the organism and the environment are known as biogeo-chemical cycles.
Nitrogen cycle: Nitrogen is a major constituent of the atmosphere. It is also an essential constituent of different organic compounds. Only few organisms like soil bacteria and blue green algae are capable of utilizing it directly in its gaseous form. Generally, nitrogen is usable only after it is fixed. 90% of fixed nitrogen is biological. The principal source of free nitrogen is action of soil micro-organisms and associated
plant roots on atmospheric nitrogen. Nitrogen can also be fixed in the atmosphere by lightning and cosmic radiation. In the oceans, some marine aniamls can fix it. After atmospheric nitrogen has been fixed into an available form, green plants can assimilate it. Dead plants and animals, excreted nitrogenous wastes are converted into nitrates by the attachment of bacteria present in the soil. They convert nitrites into nitrates that can be used by the plants again.
(ii) What is an ecological balance? Discuss the important measures needed to prevent ecological imbalances.
Answer:
Ecological balance is a state of dynamic equilibrium within a community of organisms in a habitat or ecosystem. This balance occurs through competition and co-operation between the different organisms where populations remains stable, and the fact that some species depend on others for their food and sustenance.
Important preventive measures to prevent ecological imbalances :
- Efforts should be made to preserve the species that are endangered.
- Sound planning and management is required to prevent extinction.
- Each country should identify habitats of wild relations and ensure their protection.
- Habitats where species feed, breed, nurse their young and rest should be safeguarded and protected.
- Deforestation should be prevented.