Life on the Earth class 11 geography MCQ & SAQ

Life on the Earth class 11 geography NCERT SOLUTION:

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

(a) only plants

(b) all living and nonliving organisms

(c) only animals

(d) all living organisms

Answer: (d) all living organisms

 

(ii) Tropical grasslands are also known as :

 

(a) the prairies

(c) the steppes

(b) the savannas

(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 sulfate

 

Answer: (c) iron oxides

 

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

(a) proteins

 

(b) amino acids

 

(c) carbohydrates

 

(d) vitamins

 

Answer: (c) carbohydrates

 

2. Answer the following questions in about 30 words.

 

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

Answer: 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.

Answer: Ecosystem is a system, which consists of biotic and biotic components. There are two main types of ecosystems:

terrestrial and

aquatic

 

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

Answer: A food chain is a linear network of links in a food web starting from producer organisms and ending at apex predator species, decomposer species. For example, a plant-eating beetle feeding on a paddy stalk is eaten by a frog. Fog is eaten by a snake, which is then consumed by a hawk. This sequence transfers energy from one level to another is known as the food chain.

 

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

Answer: A food web or food cycle is the natural interconnection of food chains and generally a graphical representation of what-eats-what in an ecological community. Each organism may feed on a variety of foods derived from different levels. For example, A rat feeds on various kinds of stems, roots, fruits, and grains proteins, carbohydrates, amino acids and vitamins. There is a loss of energy at each level, which may be through respiration, excretion, or decomposers.

 

(v) What is a biome?

Answer: A biome is a plant and animal community that covers a large geographical area.

 

3. Answer the following questions in about 150 word

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

Answer:

Biogeochemical cycles: A biogeochemical cycle is a pathway by which a chemical substance moves through both biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. The sun is the source of all energy on earth. A very small fraction of about 0.1 per cent of solar energy reaching earth is fixed in photosynthesis. More than half is used for plant respiration and the remaining part is temporarily stored or is shifted to other portions of the plant. During photosynthesis, carbon dioxide is converted into organic compounds and oxygen. The balance of chemical elements in the atmosphere and hydrosphere has been maintained for the last one billion years. These cycles are energized by solar Insolation. These cyclic movements are referred to as biogeochemical cycles.

Fixing of Nitrogen in the Atmosphere: Nitrogen is a major constituent of the atmosphere comprising about seventy-nine percent of the atmospheric gasses. Action of soil microorganisms and associated plant roots on atmospheric nitrogen found in pore spaces of the soil comprise the principal source of free nitrogen. Lightning and cosmic radiation can also fix nitrogen in the atmosphere.

 

(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. Ecological balance can also be explained as a stable balance in the numbers of each species in an ecosystem. It can be maintained only if the population of different organisms remains stable. It also depends on the fact that some species are interdependent on their food. For example, in the grasslands, deer, zebras, buffaloes, etc., live on grass. They provide food to carnivorous animals, such as tigers and lions, which live by hunting the herbivores. In plants, there is a change in the distribution of species. This change is 'due to competition where the secondary forest species such as grasses, bamboos, or pines overtake the native species, changing the original forest structure. This is called succession. Ecological balance is often disturbed by human interference and has led to several natural calamities like floods, landslides, diseases, climate change, etc. We need to have a proper understanding of the close relationship that exists between plants and animals for protecting and conserving ecosystems.

Life on the Earth class 11 geography MCQ :

Question : The earliest man on the earth is known as:

(a) Homoerectus

(b) Homosapien

(c) Homophobic

(d) None of the above

Answer :  B

Question : Which one of the following is not related to the formation or modification of the present atmosphere?

(a) Solar winds

(b) Differentiation

(c) Degassing

(d) Photosynthesis

Answer :  B

Question : The oceans were formed within __________ from the formation of the earth.

(a) 500 million years ago

(b) 300 million years ago

(c) 400 million years ago

(d) 200 million years ago

Answer :  A

Question : A freshwater ecosystem is

(a) Oceans

(b) Estuaries

(c) Coral reefs

(d) Marshes

Answer :  D

Question : Which biome supports the greatest variety of hoofed herbivore species?

(a) savanna

(b) tropical Savanna

(c) taiga

(d) tundra

Answer :  B

Question : Firstly life on the earth was originated in

(a) Water

(b) Air

(c) Plain land

(d) Mountains

Answer :  A

Question : Which one of the following experts gave the nebular hypothesis?

(a) Immanuel kant

(b) Laplace

(c) Chamberlain

(d) Moulton

Answer :  B

Question : Which one of the following experts gave the Collision Hypothesis?

(a) Immanuel kant

(b) Laplace

(c) Chamberlain

(d) Sir James and Harold Jeffrey

Answer :  D

Question  Big-Bang theory was postulated by

(a) Georges Lemaître

(b) Edwin Hubble

(c) Schmidt

(d) Wegener

Answer :  A

Question : The northern part of India lies in which of the following zones?

(a) Temperate region

(b) Warm Temperate region

(c) Humid region

(d) Cold region

Answer :  B

Question : Mineral salts come directly from

(a) Earth crust

(b) Water cycle

(c) Atmosphere

(d) Forest biome

 

Answer :  A

 

Question : Which one of the following experts gave the Collision Hypothesis?

(a) Immanuel kant

(b) Laplace

(c) Chamberlain

(d) Sir James and Harold Jeffrey

 

Answer :  D

 

Question : Name the multicellular animal consumers

(a) animalia

(b) annelida

(c) homosapiens

(d) none of these

 

Answer :  A

 

Question : Tropical grasslands are also known as the

(a) Prairies

(b) Savannas

(c) Steppes

(d) Velds

 

Answer :  B

 

Question : The terrestrial planets were formed in the close vicinity of the

(a) Parent star.

(b) Asteroids.

(c) Escaping gasses.

(d) Outer planets.

 

Answer :  A

 

Question : The type of soil the desert biome has is

(a) Porous with thin layers of humus

(b) Rich in nutrients with little organic matter

(c) Acidic, poor in nutrients

(d) Fertile alluvial

 

Answer :  B

 

Question : The earliest man on the earth is known as:

(a) Homoerectus

(b) Homosapien

(c) Homophobic

(d) None of the above

 

Answer : B

 

Question : Which is a plant and animal community that covers a large geographical area?

(a) Biosphere

(b) Biome

(c) Marshes

(d) Prairies

 

Answer : B

 

Question : The northern part of India lies in the

(a) Tropical zone

(b) Temperate zone

(c) Sub-tropical zone

(d) Equatorial zone

 

Answer : C

1. Abiotic factors include

(a) Producers

(b) Consumers

(c) Decomposers

(d) Sunlight

► (d) Sunlight

 

2. Mineral salts come directly from

(a) Earth crust

(b) Water cycle

(c) Atmosphere

(d) Forest biome

► (a) Earth crust

 

3. Freshwater ecosystem includes

(a) Oceans

(b) Coastal estuaries

(c) Coral reefs

(d) Streams

► (d) Streams

 

4. The boundaries of different biomes on land are determined mainly by

(a) Climate

(b) Temperature

(c) Human activities

(d) Humidity

► (a) Climate

 

5. Temperate Steppe is a subtype of which biome?

(a) Forest

(b) Desert

(c) Grassland

(d) Aquatic

► (c) Grassland

 

6. Tropical grasslands are also known as the

(a) Prairies

(b) Savannas

(c) Steppes

(d) Velds

► (b) Savannas

7. Which of the following in biology is the energy currency of cells?

(a) PDP

(b) DTP

(c) ATP

(d) ADP

► (c) ATP

 

8. A freshwater ecosystem is

(a) Oceans

(b) Estuaries

(c) Coral reefs

(d) Marshes

► (d) Marshes

 

9. Which of the following organisms have a parasitic mode of nutrition?

(a) Penicillium

(b) Plasmodium

(c) Paramecium

(d) Parrot

► (b) Plasmodium

 

10. The type of soil the desert biome has is

(a) Porous with thin layers of humus

(b) Rich in nutrients with little organic matter

(c) Acidic, poor in nutrients

(d) Fertile alluvial

► (b) Rich in nutrients with little organic matter

 

11. The earliest man on the earth is known as:

(a) Homoerectus

(b) Homosapien

(c) Homophobic

(d) None of the above

► (b) Homosapien

 

12. Which includes all the living components of the earth.

(a) Hydrosphere

(b) Atmosphere

(c) Biosphere

(d) Lithosphere

► (c) Biosphere

 

13. When various plants and animal species have got adapted through evolution is called:

(a) Ecological adaptation

(b) Hydrological adaptation

(c) Homological adaptation

(d) None of the above

► (a) Ecological adaptation

 

14. Which is a plant and animal community that covers a large geographical area?

(a) Biosphere

(b) Biome

(c) Marshes

(d) Prairies

► (b) Biome

Life on the Earth class 11 geography SAQ:

What is a bio in?

Natural ecological groups of plants and animals extend over large areas. Each of these major terrestrial ecosystems or distinctive terrestrial areas with their group of plants and associated animals are recognized as biomes. A biome is, therefore, the largest terrestrial community of plants and associated animals in interaction with the environment.

What kind of animals live in tropical rainforests?

 

The animals living in tropical rain forests include monkeys, snakes, ant-eaters, tropical birds, bats, large carnivorous animals, and a variety of fish in the rivers. Of all the species of insects known nearly 70 to S0% occur in the tropical rain forests.

 

What kind of flora and fauna characterize the deserts?

Deserts are characterized by scanty flora and fauna. Desert plants include different kinds of acacias, cacti, euphorbias, and other succulents. Ants, locusts, wasps, scorpions, spiders, lizards, rattlesnakes, a large number of insect-eating birds such as swifts and swallows, seed-eating quails, doves, desert rats, rabbits, foxes, jackals, and various cats are the common desert animals.

 

What kind of plant and animal life is supported by tropical savanna?

Savannas are characterized by coarse grass and scattered trees on the margins of the tropics where rainfall is seasonal. Wet seasons alternate with dry seasons. Plants and animals are drought-tolerant and do not show much diversity. This biome supports the greatest variety of hoofed herbivore species including the zebra, giraffe, elephant, and several kinds of antelopes. Kangaroos are found in the savannas of Australia.

 

What are the important features of the Mediterranean scrub forest as a biome?

This biome is also known as Chaparral. This is marked by very limited winter rain followed by drought in the rest of the year. The temperature is moderate under the influence of the cool, moist air of the oceans. The biome is characterized by broad-leaved evergreen vegetation. It is made up of fire-resistant resinous plants and drought-adapted animals.

 

Write a note on deciduous forests.

The deciduous forests are found in the temperate regions of north-central Europe, eastern Asia, and the eastern United States. The annual precipitation ranges between 75-150 cm. With the onset of autumn, most of the trees and shrubs become leafless. The vegetation comprises broad-leaved, hardwood trees such as oak, elm, beech, maple, and hickory. The fauna includes frogs, salamanders, turtles, snakes, lizards, squirrels, rabbits, deer, bears, raccoons, foxes, and songbirds.

 

Describe various vertical zones of the ocean.

The vertical zones of the ocean can be determined by the availability of light for photosynthesis. The lighted upper 200 meters from the photic or euphotic zone. The next zone, up to the depth of 2000 meters, gets less light which is insufficient for photosynthesis. This layer is called an aphotic zone. Below 2000 meters is the area of perpetual darkness, called the abyssal zone.

 

Distinguish between food chain and food web.

The food relation in its simplest form representing a producer, a primary consumer (herbivore), a secondary consumer (carnivore), and a decomposer is called a food chain. The next circle of such a food chain is called the food web.

 

Describe various structural components of an ecosystem.

Various structural components of an ecosystem are classified into two main groups:

1. biotic or living, and

2. abiotic or non-living.

The biotic component of an ecosystem comprises the kinds, numbers, and distribution of living organisms. The abiotic component consists of the kinds, quantity, and distribution of physical and chemical factors such as light, temperature, water, oxygen, carbon, nitrogen, and minerals.

 

Define ‘ecosystem’ with examples.

The biotic community, along with the physical environment, forms an interacting system called the ecosystem. An ecosystem can be natural or artificial, temporary or permanent. A large grassland or a forest, a small tract in a forest or a single log, an edge of the pond, a village, an aquarium, or a manned spaceship can all be regarded as ecosystems.

 

Distinguish between biotic and abiotic factors.

They are two components of an ecosystem. The biotic component comprises the kinds, numbers, and distribution of living organisms. The abiotic component, on the other hand, consists of the kinds, quantity, and distribution of physical and chemical factors such as light, temperature, water, oxygen, carbon, nitrogen, and minerals.

 

Explain with examples the role of members of the fungi kingdom of organisms.

The fungi kingdom includes diverse kinds of multicellular heterotrophic organisms. There are over 100,000 species of fungi. Some are unicellular like yeast, others are complex like mushrooms. The fungi are the major decomposers and their activity is essential for the recycling of inorganic resources in the biosphere.

 

What do you understand about biogeochemical cycles?

The balance of the chemical elements in the atmosphere and hydrosphere is maintained by a cyclic passage through the tissues of plants and animals. The cycle starts by absorbing chemical elements by the organism and returning back to air, water, and soil through decomposition. These cycles are energized by solar insolation. These cyclic movements of chemical elements of the biosphere between the organism and the environment are referred to as biogeochemical cycles.

 

What is the hydrologic cycle?

All living organisms, the atmosphere, and the lithosphere maintain between them a circulation of water in solid, liquid, or gaseous form, referred to as water or hydrologic cycle.

 

What is denitrification?

Herbivorous animals feeding on plants in turn consume some of it. Dead plants and animals, excreted nitrogenous wastes are converted into nitrites by the attachment of bacteria present in the soil. Some bacteria can even convert nitrites into nitrates that can be used again by the green plants. There are still other types of bacteria capable of converting nitrates into free nitrogen, a process known as denitrification.

Life on the Earth class 11 geography :

“Food chains are not isolated linear chains of trophic levels.” Comment.

In nature, the food relationship cannot be explained only in terms of a single food chain. A herbivore consumes many types of plants or plant products. Many kinds of animals, other than tigers, derive food from herbivorous animals. Ticks and mites, leeches, and blood-sucking insects are dependent on herbivores and even on carnivores. Thus, food chains are not isolated linear chains of trophic levels.

Depending upon the availability and choice of food, different organisms at each level have a food relationship with more than one organism at the lower levels. A rat, for example, feeds on various kinds of stem, roots, fruits, and grains. In turn, it is consumed by a snake which is eaten by a falcon. The snakes feed on both frogs and rats. Then, a network of food chains exists, which is called a food web. The food web becomes more complicated when taste and preference, availability, and compulsion are involved.

 

Describe the functions of various biotic components.

Various biotic components include producers, herbivores, carnivores, and decomposers. All organisms require energy for their life processes. Food supplies both energy and materials for the sustenance of life. Green plants produce carbohydrates by photosynthesis and also synthesize proteins and fats. The green plants, therefore, are called producers. The animals that consume this energy are called consumers.

The herbivores like cattle, deer, and goats derive their food or energy directly from plants and are called the first-order consumers. The carnivores like tiger and lion depend on herbivores for their food and energy and are therefore called the secondary or second-order consumers. The non-green organisms like fungi and some bacteria, which do not produce their own food, live on the dead and decaying plants or animals and are consumers of a special type called decomposers.

 

Describe the energy flow in the biosphere.

Energy from the sun enters the living world through photosynthetic organisms and passes on from one organism to another in the form of food.

The organisms which trap solar energy and act as producers also use some energy for their own life processes. Only a portion of the energy trapped is taken by the primary consumers. Animals being more active than plants use much of the energy acquired before they are consumed by the next trophic level. At each stage of energy transfer, some amount of energy is lost from the food chain. The amount of energy transferred to the next higher level thus gradually decreases. The decomposition of dead organisms also releases chemical energy. Eventually, all this solar energy that entered the living system through the producers goes back into the non-living world, not as light but as heat.

 

Describe the carbon cycle in brief.

Carbon is one of the basic elements of all living organisms. It forms the basic constituent of all organic compounds. The biosphere contains over half a million carbon compounds. The carbon cycle is mainly the conversion of carbon dioxide. This conversion is initiated by the fixation of carbon dioxide from the atmosphere through photosynthesis. Such conversion results in the production of carbohydrates, glucose that may be converted to other organic compounds such as starch, cellulose, etc. Here, some of the carbohydrates are utilized directly by the plant itself. During this process, more carbon dioxide is generated and is released through its leaves or roots during the day. The remaining unutilized carbohydrates become part of the plant tissue.

The plant tissues are either eaten by the herbivorous animals or decomposed by microorganisms. The herbivores convert some of the consumed carbohydrates into carbon dioxide for release into the air through respiration. The microorganisms decompose the remaining carbohydrates after the animal dies. The carbohydrates that are decomposed get oxidized into carbon dioxide and are returned back to the atmosphere.