NCERT Class 11 Geography Chapter 15 Life on The Earth

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NCERT Class 11 Geography Chapter 15 Life on The Earth

Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. CBSE Class 11 Geography Solutions are part of All Subject Solutions. Here we have given NCERT Class 11 Geography Part I: Fundamentals of Physical Geography, Part II: Indian: Physical Environment, Part III: Practical Work in Geography. NCERT Class 11 Geography Chapter 15 Life on The Earth Notes, NCERT Class 11 Geography Textbook Solutions for All Chapters, You can practice these here.

Life on The Earth

Chapter: 15

GEOGRAPY [ PART – I ]

SHORT ANSWER TYPE QUESTIONS

Q.1. Define biosphere.

Ans. The biosphere consists of all the living components of the earth-plants, animals, micro-organisms and their interactions with the surrounding environment. Thus it includes whole of the region of the earth- that is inhabited by the living organisms-lithosphere and /or the hydrosphere as well as atmosphere.

Q.2. How does humidity affect plant life?

Ans. The humidity in the atmosphere directly regulates the rate at which water evaporates from the body surface of land organisms by transpiration, perspiration and other life- processes. Plants and animals have different levels of adaptations to withstand dry conditions.

Q.3. What are the functions of fungi?

Ans. The fungi are the major decomposers and their activity is essential for the recycling of inorganic resources in the biosphere. The fungi and some other bacteria which do not produce their own food live on the dead and decaying plants or animals. In this way they function to make the environment clean and fresh.

Q.4. What is an ecosystem?

Ans. All organisms whether belonging to the plant kingdom or the animal kingdom interact with each other as well as with their physical environment. The complex system of interactions between organisms and their physical environment in any unit of area is referred to as an ecosystem.

Q.5. Explain food chain with examples.

Ans. The transfer of energy from one organism to another in the ecological systems forms a food-chain. For example, in a grass-lands, herbivores, such as the deer, feed on the grasses and at the next stage carnivores such as the lions, feed on the deer. The food-chain thus involves the flow of energy from the lower to higher levels.

Q.6. Name the part of the earth in which all life forms exist.

Ans. Biosphere.

Q.7. Why is biosphere important?

Ans. Biosphere is important because life of any kind is possible only in biosphere.

Q.8. Name the categories of the organisms.

Ans. The two categories of organisms are:

1. Plant kingdom.

2. Animal kingdom.

Q.9. Who are Homo Sapiens?

Ans. The modern man is known as Homo Sapiens.

Q.10. Name the system which comprises of the physical environment and the organisms which live therein.

Ans. Ecosystem.

Q.11. Name the two categories of components of an ecosystem.

Ans. Two components of an ecosystem are:

(i) Biotic components.

(ii) Abiotic components.

Q.12. Which are the three categories of organisms?

Ans. 1. Producers.

2. Consumers.

3. Decomposers.

Q.13. Name the three most important elements found in all living organisms.

Ans. 1. Carbon.

2. Oxygen.

3. Hydrogen.

Q.14. Which kingdom does bacteria belong to?

Ans. Monera Kingdom.

Q.15. On what criteria the classification of kingdoms is done?

Ans. The classification of kingdoms is made on the following criteria:

1. Complexity of cell structure.

2. Complexity of organism’s body.

3. Mode of obtaining nutrition.

Q.16. What are three inorganic realms of the earth where life is present?

Ans. Lithosphere, Atmosphere and Hydrosphere.

Q.17. What is species diversity?

Ans. The variation in the physical features of species.

Q.18. What are algae? Mention their common characteristics and types.

Ans. Algae are primitive plants in which the body is not divided into roots, stems and leaves. These are green and thus autotrophic in nature. Algae can prepare their own food in the form of glucose. The food is stored in the form of starch. The algae reproduce a sexually by zoospores and sexually by gametes.

Q.19. On what factors does the nature of biome depend?

Ans. Rainfall, temperature, humidity and soil conditions.

Q.20. Name the major grasslands of the world.

Ans. 1. Prairies.

2. Pampas.

3. Steppe.

4. Veld.

5. Downs.

Q.21. What are the common desert plants?

Ans. Desert plants include different kinds of acacias, cacti, euphorbia’s and other succulents.

Q.22. What are the three major groups into which plants are put on the basis of water requirements?

Ans. (i) Xerophytes.

(ii) Hydrophytes.

(iii) Mesophytes.

Q.23. What are zooplanktons?

Ans. Tiny animal organisms living in ocean waters are called zooplanktons.

Q.24. What do you mean by deciduous forests?

Ans. Forests where the trees shed their leaves during a part of the year are called deciduous forests.

Q.25. What are xerophytes?

Ans. Plants which are able to survive in dry regions are called xerophytes.

Q.26. What is estuary?

Ans. Estuary is a zone of mixing of fresh and salty water.

Q.27. What are planktons?

Ans. A number of organisms which have no measured population.

Q.28. What are aquatic eco-systems?

Ans. Aquatic ecosystems include fresh water lakes, rivers, estuaries, neritic zones, etc. The concentration of dissolved oxygen and the sunlight penetration of water and availability of nutrients are limiting factors for aquatic organisms.

Q.29. What are detritus feeders?

Ans. A fourth group of consumers feeding in the ocean waters or decomposed tissues of plant, animals are called detritus feeders.

Q.30. What are the functions of benthonic fauna?

Ans. The benthonic fauna has fewer producers and more and more consumers, scavengers and decomposers. They help in cleaning the environment by eating the dead animals and organisms.

Q.31. Describe ecological efficiency.

Ans. The percentage of energy transferred from one trophic level to another is called ecological efficiency. The efficiency of energy transfer from one trophic level to another varies from 5% to 20% depending on the types of organisms and environmental conditions.

Q.32. Mention the chief characteristics of the neritic province.

Ans. The surface area of the sea upto the depth of 200 metres comprises neritic province. It is characterised by shallow depths, low salinity, less turbulent motion and more of plant nutrients. The light can penetrate into the sea only upto the neritic provinces.

Q.33. Why does population of marine organisms decreases with depth?

Ans. The population of organisms decreases with the increasing distance from the coast. Most organisms in the deep sea zone are carnivorous, living on the organic debris of dead organisms.

SHORT ANSWER TYPE QUESTIONS

Q.1. What is an ecological system? Identify the major types of ecosystems in the world.

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

There are two major types of ecosystems:

(i) Terrestrial. and

(ii) Aquatic ecosystem.

Q.2. Mention five kingdoms into which different organisms are divided.

Ans. The five kingdoms are as under:

1. Monera (Single cell microscopic organisms).

2. Protista (Unicellular, mainly aquatic organisms).

3. Plantae (Multicellular photosynthetic plants).

4. Fungi (Multicellular decomposers).

5. Animalia (Multicellular animal consumers).

Q.3. What is a food-chain? Give one example of a grazing food-chain identifying the various levels.

Or

What is food-chain? Describe it with (2016) example.

Ans. The sequence of eating and being eaten with the resultant transfer of energy from one level to another level is known as food chain.

The example is that the plants and grass is eaten by a deer and the deer is being eaten by lion. In this way the energy is transferred from one level to another.

Q.4. What is biome?

Ans. A biome is a plant and animal community that covers a large geographical area. Therefore a biome is a total assumblage of plant and animal species. There are five major biomes -forests, deserts, grasslands, aquatic and altitudinal.

Q.5. Explain the significance of phytosynthesis. 

Ans. Consumers depend on producers for their food. The primary producers are green plants as they produce organic matter utilising sun’s radiant energy. The presence of green pigment called chlorophyll in the leaves of plants makes photosynthesis possible. Without the process of photosynthesis, the green plants will not exist and with green plants, the primary consumers will dry up and without them the secondary consumers will die. The result will be that the life will not exist on the earth.

Q.6. Explain the term ‘Ecological Pyramid’.

Ans. Each group of organisms occupies a feeding level called a trophic level. The different trophic levels may be represented in the form of a pyramid called ecological pyramid.

Man is at the top of the ecological pyramid. The pyramid has a large base. It represents primary producers. From base to the top, the numbers go on decreasing at each trophic level. All green plants and other producers occupy the first trophic level. Herbivores which feed on plants occupy the second trophic level. Carnivores that eat herbivores are at the third trophic level. At each level, the flow of energy is reduced; because only a fraction of energy is transferred from lower to higher level.

Q.7. What do you understand by the term ‘ecology’?

Ans. Ecology is the study of the earth as a household of plants, animals and microorganisms. They all live together as interdependent components. In the words of Earnest Hackles “The study of interaction between lifeforms (biotic) and physical environment (abiotic) is the science of ecology”.

Q.8. What do you understand by the term ‘food web’? Give examples.

Ans. Many simple food chains intermingle with one another to form a food web. In other words the interconnecting network of food chains is known as a food web. For example a mouse feeding on grain may be eaten by different secondary consumers (carnivores) and these carnivores may be eaten by another set of different tertiary consumers.

Q.9. Mention characteristics of Savanna biomes.

Ans. Savanna are characterized by coarse grass and scattered trees on the margins of the tropics where rainfall is seasonal and wet seasons alternate with dry season. This biome supports the greatest variety of animals, such as zebra, giraffe, elephant, etc.

Q.10. What are photic and aphotic zones?

Ans. Photic zone: The vertical zone of the ocean are determined by availability of light for photosynthesis. The lighted upper 200 metres forms the photic zone.

Aphotic zone: The next zone upto the depth of 2000 metres gets less light which is insufficient for photosynthesis. This layer is called aphotic zone.

Q.11. Why are the marine animals able to live at a great depths than the marine plants?

Ans. The marine animals are able to live at great depths where there is a permanent darkness. The major fauna of marine comprise porifera, coelonterates, molluscs, marine worms, fishes and sea-snakes. The marine fishes have energetic organs, phophorescent organs, like glands and sensitive arms to live safely in the deep sea environment. As the marine animals do not need sunlight for their survival, they are able to live at great depths.

Q.12. What do you know about man made ecosystem?

Ans. We know how humans have changed the environment to a far greater extent than any other species. In some instances the modification is so profound that we call them man-made or artificial ecosystem. Villages and cities, orchards and gardens, parks with their animals are man-made terrestrial ecosystem. Large dams and reservoirs, lakes, canals are examples of man-made aquatic eco-systems.

Q.13. Explain agro-ecology.

Ans. The study of the relation between agricultural crops and environment is called agro-ecology. The physical conditions as well as the biotic communities of different croplands vary widely. Since there are some common features that mark all croplands, they are generally called agro-eco systems. The physical conditions of the farm depend upon latitude, overall climatic and ecological factors. The type of crops depends upon the climatic season and choice of the farmer. Animal population of cultivated lands comprises earth worms, nematodes, domestic animals, insects and many birds.

Q.14. Describe fresh water environment and mention plants and animals that live therein.

Ans. The fresh water bodies are lakes and ponds. They vary in size from less than a hectares to hundreds of hectares. The relatively shallow lakes called eutrophic lakes have a rich accumulation of organic products.

Streams and rivers: They differ widely in volume of water, speed of flow and oxygen content, etc. The nature and composition of flora and fauna depends on the source of the river and the land environment. Floating population of planktons are generally absent in such waters. Sediments are deposited on the river bed. The total volume of water is also larger. The surface gets more sunlight raising the temperature of water. The water often is muddy cutting down light at the river bed. Many reptiles, mammals and birds obtain their food from the water therein.

Q.15. What is the relationship between animal life and vegetation in a region?

Ans. There is a close relationship between animal life and vegetation in a region. Vegetation not only provides food but also suitable habitat for animals. Animals have to move from place to place in search of food. Animals in tropical forests are adapted to live among trees, for example apes and monkeys can climb trees because of their long limbs and small deer can move freely between trees. In the cold Tundra region animals have thick skins to protect them from cold.

Q.16. Write short notes on the following:

(i) Altitudinal biomes.

Ans. A series of biomes can be noted along the slopes of high mountain ranges like the Himalayas, Andes and Rockies. These mountain ranges have the gradual change in the biome-type according to the altitude rather than the latitude. Temperature and precipitation rates are most important determinants of these biomes. In the tropical mountains the sequence of communities and conditions from the base of the mountain to the snow-line are tropical forest, deciduous forest, coniferous forest and Tundra.

(ii) Oligotrophic lakes.

Ans. The deep lakes with steep and rocky sides and poor in circulating nutrients such as phosphates are called oligotrophic lakes. The physical factors of the lakes contain saline or brackish water (Sambar lake of Rajasthan).

(iii) Boundaries of Ecosystem.

Ans. An ecosystem is an area in which the living and nonliving components can be demarcated by a boundary, for convenience in study. It is important to recognise that ecosystem are not strictly isolated. Their boundaries are indistinct and overlapping. Some movement always occurs from one ecosystem to another in terms of energy and materials. This movement may be from an adjacent or distant ecosystem. A pond may be separated from a grassland but some birds may break the barrier and feed on the fishes of the pond. The top soil from the Himalayas is washed down in massive amount by rivers. Siberian crane can migrate from Siberia to Bharatpur in India.

(iv) Nektons.

Ans. Nektons are the swimming organisms and include fishes, whales, dolphins, porpoises and other animals. Nektons feed primarily on zooplanktons which live below the surface where food is plentiful. Many plant-eating nektons come on the surface only at night to feed on planktons. Nektons always move from place to place and from one depth to another in search of food and for breeding. Some move in cold water and other either in warm water or in the entire ocean. Nektons are an advanced form of animals in relation to planktons and benthos. Dolphins and porpoises are among the most intelligent animals of the world. Dolphins have been successfully trained in some parts of the world to carry messages, mail and tools from one place to another.

Q.17. Distinguish between.

(i) Terrestrial and Aquatic Ecosystems,

Ans. Terrestrial Ecosystem: Natural ecological groups of plants and animals extend over large areas. Each of major terrestrial ecosystem or terrestrial areas with their group of plants and associated animals, have different type of biomes including tropical rainforests, Savanna, Mediterranean, deciduous, grasslands, deserts, taiga and tundra.

Aquatic Ecosystem: There are many kinds of aquatic ecosystems that differ widely with regard to abiotic factors. The aquatic eco- systems range from open ocean to small temporary puddles, have conditions of salinity, depth and fluctuations of temperature.

(ii) Marine and Fresh water environ-ment.

Ans. Marine environment: The marine environment is characterised by high concentration of salt and mineral ions. The salt concentration in the open sea is about 3.5 per cent. Salinity of the surface water and the water at various depths and latitudes varies. Salinity is least near the poles and river mouths. The sea is not a single environment. More important determinants of marine ecosystems are depth of water, distance from the shore and drainage of glaciers and rivers.

Fresh water environment: Lakes and ponds are stagnant fresh water bodies and occur particularly in every biome. They vary in size from less than a hectare to hundreds of hectares. The relatively shallow lakes called eutrophic lakes, have a rich accumulation of organic products. The fresh water ponds are called autotrophs and have microscopic phytoplanktons.

Streams and rivers differ in volume, temperature etc. The nature and composition of flora and fauna depend on the source of river and the land environment.

(iii) Taiga and Tundra bioms.

Ans.

Taiga	Tundra
1. These are coniferous forests.	1. Tundra consists of plains characterised by snow and ice.
2. Pine, fur, cedar and spruce are the trees.	2. There is poor light and extremely low temperature. Snowfall is scanty.
3. In some areas trees are so dense that little light reaches the floor.	3. Vegetation is so sparse that it is also called the arctic desert.
4. This biome is good habitat for elks, deer, geese, rabbits, pumas, lynx and many insects.	4. This biome is virtually treeless.

(iv) Mid-latitude Evergreen Forests and Mediterranean Forests.

Ans.

Mid-latitude Evergreen Forests	Mediterranean Forests
1. These forests are found in the subtropical belts.	1. These forests are found in the middle latitudes.
2. These forests are found in the eastern margins of the continents.	2. These forests are found in the western margins of the continents.
3. In these forests, plants have broad leaves.	3. Trees of these forests are having small leaves.
4. No shrubs are found in between the trees.	4. Shrubs occur in between the trees.
5. Oak, eucalyptus and wattle are the examples of such forests.	5. Cork, oak, olive and chestnut are the examples of Mediterranean forests.

(v) Tropical Deciduous Forests and Mid-latitude Deciduous Forests.

Ans.

Tropical Deciduous	Mid-latitude Deciduous Forests
1. These forests occur in sub-tropical regions with a distinct dry season.	1. These forests occur in the coastal regions of cool climates.
2. Trees shed their leaves in the dry season.	2. Trees shed their leaves in winter season.
3. They are found in the regions of Western Europe, North-Eastern China, Japan, North-Eastern U.S.A, Southern China and New Zealand.	3. They are found in the monsoon regions of Asia, parts of central America, Brazil and northern Australia.

(vi) Desert-type vegetation and Tundra-type vegetation.

Ans.

Desert-type Vegetation	Tundra-type Vegetation
1. This vegetation is found in dry regions having low rainfall.	1. This vegetation is found in snow covered areas.
2. This vegetation is found in tropical desert areas like north Africa.	2. This vegetation is found around North Pole in Eurasia and North America.
3. Cacti, thorny bushes and coarse grasses are the examples of desert-type vegetation.	3. Mosses, lichens and wild flowering shrubs are the examples of tundra-type vegetation.

(vii) Tropical Grassland and Mid-latitude Grassland.

Ans.

Tropical Grasslands	Mid-latitude Grassland
1. These grasslands occur in the interiors of continents in the tropical zone.	1. These grasslands occur in the interiors of continents in the middle latitudinal zone.
2. These grasses are long grasses, about two metres in height.	2. These grasses are short grasses.
3. Major regions are the equatorial regions in Africa, parts of Brazilian plateau, Deccan plateau and northern Australia.	3. Major regions are Russia, interiors of United States and Canada, South African plateau, coastal plains of Argentina and Uruguay in South America and Murray-Darling basin in Australia.
4. These grasslands are known as Savanna in Africa and Pampas in Brazil.	4. These are known as steppes in Eurasia, Prairies in North America and Pampas in South America.

Q.18. What is an ecological balance? Discuss the important measures needed to prevent ecological imbalances.

Ans. Ecological balance is a state of dynamic equilibrium within a community of organisms in a habitat or ecosystem.

Ecological Imbalances: Ecological balance may be disturbed due to introduction of new species, natural hazards or man-made causes. Some measures should be taken to check these imbalances:

1. Man’s interference should be rational.

2. Population should be controlled.

3. Afforestation should be encouraged.

4. Efforts should be made to preserve the species that are endangered.

5. Prevention of extinction requires sound planning and management.

Causes of Imbalances:

(i) Ecological balances may be distributed due to the introduction of new species natural hazard or manmade causes.

(ii) Man’s interference has affected the balance of plant communities leading to disturbances in the eco-systems. Such disturbances bring about numerous secondary successions.

(iii) Human pressure on the earth’s surface has put a heavy toll on the ecosystem. This has destroyed its originally and had caused adverse effects to the general environment.

(iv) Ecological imbalances have brought many natural calamities like floods, landslides diseases, erratic climate occarances and such other hazards.

LONG ANSWER TYPE QUESTIONS

Q.1. What are biogeochemical cycles? Explain how nitrogen is fixed in the atmosphere.

Ans. The cyclic movements of chemical elements of the biosphere between the living organisms and the environment are referred to as biogeochemical cycles. Bio refers to living organisms and geo refers to rocks, soil, air and water on the earth.

Nitrogen is a major constituent of the atmosphere comprising of about 78% of the atmospheric gas. Generally nitrogen is usable only after it is fixed. Ninty percent of fixed nitrogen is biological. The principal source of free nitrogen is the action of soil microorganisms and associated plant roots on atmospheric nitrogen found in pore spaces of the soil. Nitrogen can also be fixed in atmosphere by lightning and cosmic radiation.

Q.2. Describe the global distribution of biomes.

Ans. Forests, grasslands, thorny shrubs and tundra are major plant biomes.

Forest Types: Forests are classified into two types:

1. Evergreen. and

2. Deciduous Forests.

1. Evergreen Forests: These forests remain green throughout the year, as there is no mass shedding of leaves throughout the year. Evergreen forests are of the following types:

(i) Tropical Evergreen Forests: These occur in equatorial regions and tropical coastal regions having heavy rainfall. There is a luxuriant growth and variety of vegetation. Trees have broad leaves. Mahogany, ebony and rosewood are of commercial value among tropical evergreen trees.

(ii) Mid-latitude Evergreen Forests : These forests occur in western margins of continents in middle latitudes. Here rainfall is received in winter and the summer is dry. Plant have spiny, waxy or small leaves to reduce transpiration. Trees are widely spaced and shrubs occur in between. Cork, oak, olive and Chestnut are the examples.

(iii) Coniferous Forests: They are found around the north polar region, Europe, Asia and North America. Trees are tall and conical in shape. They have thick needle-shaped leaves to reduce transpiration and to protect them from cold winter.

2. Deciduous Forests: Trees shed their leaves in a particular season to conserve loss of moisture. Deciduous forests are of the following types:

(i) Tropical Deciduous Forests: These are found in subtropical regions with a distinct dry season. These forests have fewer species and are less dense. Teak is a valuable hardwood tree found in these forests. These are found in monsoon regions of Asia, central America, Brazil and northern Asia.

(ii) Mid-latitude Deciduous Forests: These occur in coastal regions of cool climates. Trees shed their leaves in winter when temperature is below 6°C. These occur in the region of western Europe, north-eastern China, Japan, north-eastern United States etc.

3. Grasslands: Grasses are shallow rooted plants which thrive under varying climatic conditions. They are divided into tropical grasslands and mid-latitude grasslands.

(i) Tropical Grasslands: These occur in the interiors of continents in the tropical zone. These grasses are tall, about 2 metres in height. These are found in equatorial regions of Africa, Brazilian Plateau, Deccan Plateau etc.

(ii) Mid-latitude Grasslands: These occur in the interiors of continents in mid- latitudes receiving moderate rainfall. These grasses are short and trees are absent. These are found in regions of Russia, U.S.A., Canada and South African plateau.

4. Desert Vegetation: This vegetation occurs in regions of low rainfall. Short shrubs occur in patches. Cacti, thorny bushes and coarse grasses are found in deserts.

5. Tundra Vegetation: This type of vegetation occurs around the North Pole in Eurasia and North America. Patches of mosses, lichens, wild-flowering shrubs are seen. The land is snow-covered during the long winters.

Q.3. Describe major ecosystems of the earth.

Ans. The ecosystems of the earth may be divided into two major types-Aquatic Ecosystems and Terrestrial Ecosystems.

Aquatic Eco-systems: Aquatic ecosystems include fresh water lakes, rivers, estuaries, neritic zones, etc. The concentration of dissolved oxygen and the sunlight penetration of water and the availability of nutrients are limiting factors for aquatic organisms.

Fresh Water Lakes: These are deep; there are two zones: 

(i) surface layer. and

(ii) bottom layer.

Surface layer is warm and exposed to sunlight penetration while bottom layer is cold. Surface layer is rich in oxygen and bottom layer is rich in nutrients. Seasonal mixing of water between these two layers enables the survival and growth of organisms. These have variety of plants and water birds.

Rivers: Rivers have wide variety of organisms. In the upper layer aquatic plants and animals are anchored to rocky surfaces. In the lower reaches, layers of alluvial sediments provide habitats for burrowing animals and bottom feeders.

Estuaries: These are the most productive among the aquatic ecosystems. Because of sunlight penetration, tidal action which enable mixing of nutrients, there is a luxuriant plant growth. Thus a variety of organisms like crabs, Oyesters, shrimps, fishes and birds etc. are found.

Neritic Zones: These zones are the richest fishing grounds. Beyond the edge of the continental shelf productivity is low thus open oceans are biological deserts.

Terrestrial Ecosystems: These are of greater concern because we live on land and needs for our food and other materials are met from terrestrial ecosystems. The surface of the land has a cover of vegetation of different kinds depending on climatic conditions such as moisture, temperature, etc. Plants occur in distinct groups of communities in areas having similar climatic conditions and these are called biomes.

Q.4. Give an account of the factors which influence the terrestrial ecosystem.

Ans. Terrestrial Ecosystem : Ecosystems which prevail on the land are called terrestrial ecosystems. They are of special importance to us because all our needs for food and other materials are met through them.

Factors which affect the terrestrial ecosystems: There are many factors which affect the terrestrial ecosystems and thereby the cover of vegetation on the land.

Moisture: Moisture provided by water plays an important part in plant growth because all the nutrients required for growth are supplied to the plants in the dissolved state through the medium of water from the roots to the leaves.

Water helps not only in the process of photosynthesis but also in germination, growth and reproduction of plants.

Temperature: Along With water, temperature also plays an important part in the germination, growth and reproduction. But temperature is required within limits beyond which the plants cannot survive. In deserts, plants do not grow in most part of the year because of excessive heat.

Soil: Soil is also an important factor in plant growth. There are different types of soils-sandy soil, loamy soil, black soil. Black soils have proved very suitable for the cultivation of cotton while loamy soils are good for the cultivation of wheat, rice, sugarcane, etc. Some soils can retain moistures for a longer period than the others and thus they prove useful for certain types of crops.

Other Factors: There are some other factors like drainage and relief features which affect the type of vegetation and the terrestrial ecosystem. As for example, in the mountain regions the type of vegetation varies according to altitude.

Q.5. Describe the important characteristics of the different forest biomes of the world.

Ans. Forests biomes are-Tropical, Temperate and Boreal. 

Characteristics of Tropical Forests: These are of two types Tropical Rainforests.

Tropical Rainforests: Tropical Deciduous Forests.

1. Tropical Rainforests are found near the equator (10° N and S).

2. The temperature is 20°C to 25°C and the rainfall is about 200 cm.

3. Trees are usually large and tall and make canopy.

Tropical Deciduous Forest:

1. Tropical deciduous forests occur 10°-25°N and S. Latitudes.

2. Rainfall is about 100 cm.

3. Trees are of medium height.

Characteristics of Temperate forests:

1. These are found in North America, north eastern Asia and western and central Europe.

2. Annual range of temperate is -30° to 30°C.

3. Rainfall is about 75 cm to 150cm.

4. Trees have normally broad-leaves.

Characteristics of Boreal forests:

1. These are found between 50°-60° latitude in Northern Hemisphere.

2. Temperatures are usually very low.

3. The precipitation is in the form of snow.

4. These are also called taiga forests.