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- CBSE Class 7 Social Science Book
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- CBSE Class 7
- Social Science
Natural vegetation refers to a plant community which has grown naturally without human aid and has been left undisturbed by humans for a long time.
(i) Our country India is one of the twelve mega-bio-diversity countries of the world.
(ii) There are about 47,000 plant species.
(iii) There are about 15,000 flowering plants.
(iv) India also has 89,000 species of animals as well as a rich variety of fish in its fresh and marine water.
* Factors Effecting Natural Vegetation
(i) The growth of vegetation depends on temperature and moisture.
(ii) It also depends on factors like slope and thickness of soil.
(iii) The type and thickness of natural vegetation varies from place to place because of the variation in these factors.
(i) The nature of land influences the type of vegetation. The fertile level is generally devoted to agriculture.
(ii) The undulating and rough terrains are areas where grassland and woodlands develop and give shelter to a variety of wild life.
(i) Different types of soils provide basis for different types of vegetation.
(ii) The sandy soils of the desert support cactus and thorny bushes while wet, marshy, deltaic soils support mangroves and deltaic vegetation.
(i) The character and extent of vegetation are mainly determined by temperature.
(ii) On the slopes of the Himalayas and the hills of the Peninsula above the height of 915 metres, the fall in the temperature affects the types of vegetation and its growth.
Areas of heavy rainfall have more dense vegetation as compared to other areas of less rainfall.
* Photoperiod (Sunlight)
The variation in duration of sunlight effects the vegetation. Due to longer duration of sunlight, trees grow faster in summer.
Natural vegetation is generally classified into three broad categories as follows :
Forests: Grow where temperature and rainfall are plentiful to support a tree cover. Depending upon these factors, dense and open forests are grown.
Grasslands: Grow in the region of moderate rain.
Shrubs: Thorny shrubs and scrubs grow in the dry region.
The changes in the type of natural vegetation occur mainly because of the changes of climatic condition.
* Tropical Evergreen Fores
These forests are also called tropical rainforests. These thick forests occur in the regions near the equator and close to the tropics in the Amazon basin, Zaire basin, Malaysia, Myanmar, Kampuchea, Vietnam, Indonesia.
(i) These regions are hot and receive heavy rainfall throughout the year. As there is no particular dry season, the trees do not shed their leaves altogether. This is the reason they are called evergreen. These forests trees reach great heights up to 60 metres.
(ii) The thick canopies of the closely spaced trees do not allow the sunlight to penetrate inside the forest even in the day time.
(iii) There are no pure stands of trees but all the species are intermixed which make Commercial Exploitation of these forests very difficult.
Hardwood trees like rosewood, ebony, mahogany are common here.
Animals and Birds found in these forests are elephants, monkey, lemur and deer, one horned rhinoceros, Bats, sloth, scorpions and snails.
* Tropical Deciduous Forests
Tropical deciduous are the monsoon forests found in the large part of India, northern Australia and in central America.
(i) These regions experience seasonal changes. Trees shed their leaves in the dry season to conserve water.
(ii) These forests consist of trees with High Commercial Value. These forests are not very dense and the trees are of medium height.
(iii) Hardwood trees are extremely useful for making furniture, transport and constructional materials.
The hardwood trees found in these forests are sal, teak, neem and shisham.
Tigers, lions, elephants, langoors and monkeys are the common animals of these regions.
* Temperate Evergreen Forests
The temperate evergreen forests are located in the mid-latitudinal coastal region. They are commonly found along the eastern margin of the continents, e.g., in south east USA, South China and in South East Brazil.
These forests have a Mixed Variety of trees. The Timber from these forests is valuable.
They comprise both hard and soft wood trees like oak, pine, eucalyptus, etc.
The people living in these parts of the world rear cattle, pigs and sheep - largely for wool, meat and skins.
* Temperate Deciduous Forest
Forest are found in the north eastern part of USA, China, New Zealand, Chile and also found in the coastal regions of Western Europe.
(i) The cool climate of this region is favourable for the forest growth. The trees are generally Deciduous in nature. Most of the trees have thick trunks and broad leaves.
(ii) They shed their leaves in autumn and remain leafless during winter.
Important Trees and Animals:
The common trees are oak, ash, beech, etc. Deer, foxes, wolves are the animals commonly found. Birds like pheasants and monals are also found here.
* Mediterranean Vegetation
(i) The west and south west margins of the continents have Mediterranean vegetation.
(ii) It is mostly found in the areas around the Mediterranean Sea in Europe, Africa and Asia, hence the name.
(iii) This kind of vegetation is also found outside the actual Mediterranean region in California in the USA, south west Africa, south western South America and South west Australia.
(i) These regions are marked for hot dry summers and mild rainy winters.
(ii) Citrus fruits such as oranges, figs, olives and grapes are commonly cultivated here because people have removed the natural vegetation in order to cultivate what they want to. There isn’t much wildlife here.
(iii) The trees have broad leaves and are widely spaced. They are not thick and luxuriant. They are not very tall. The trees have adapted themselves to the long dry summer season.
* Coniferous Forests
In the higher latitudes (50° - 70°) of Northern hemisphere the spectacular Coniferous forests are found. These are also called as Taiga. These forests are also seen in the higher altitudes. These are the trees which Salima found in the Himalayas in abundance.
Uses of Trees:
They are tall, softwood evergreen trees. These woods are very useful for making pulp, which is used for manufacturing paper and newsprint. Match boxes and packing boxes are also made from softwood.
Important trees and Animals:
Chirr, pine, cedar are the important variety of trees in these forests. Silver fox, mink, polar bear are the common animals found here.
* Tropical grasslands
These grow on either side of the equator and extend till the tropics.
(i) This vegetation grows in the areas of moderate to low amount of rainfall. They can grow very tall, about 3 to 4 metres in height. Savannah grasslands of Africa are of this type.
(ii) The Tall and Thick Grass grows here with Scattered Trees. Cattle rearing is carried out on these grasslands.
Elephants, zebras, giraffes, deer, leopards are common in tropical grasslands.
* Temperate grasslands
These are found in the mid-latitudinal zones and in the interior part of the continents.
(i) These grasslands are known by different local names, such as Prairies in North America, Pampas in Argentina, Veld in South Africa, Steppes in Russia and Downs in Australia.
(ii) These areas do not get sufficient amount of rainfall that is why Short Grass grows here with Scattered Trees. Cattle are reared in these grasslands. Usually, grass here is short and nutritious.
Wild buffaloes, bisons, antilopes are common in the temperate region.
* Desert Vegetation (Shrubs)
* Thorny bushes
These are found in the dry desert like regions. Tropical deserts are located in the western margins of the continents.
(i) The vegetation cover is scarce here because of scanty rain and scorching heat.
(ii) Truly speaking, there are no forests here. Only the Xerophytes, the plants which adapt themselves to the hot and dry climate, are available.
Important Trees and Animals:
Palm, Cactus and thorny bushes are found here. Camel, Hyena, Fox, Jackal, Wild asses, Reptiles, Lizards, Snakes are the animals common in desert.
* Tundra Vegetation
This vegetation is found in the polar areas of Europe, Asia and North America.
(i) The polar region is extremely cold. The growth of natural vegetation is very limited here.
(ii) Only mosses, lichens and very small shrubs are found here. It grows during the very short summer. This is called Tundra type of vegetation. The animals have thick fur and thick skin to protect themselves from the cold climatic conditions.
Seal, Walruses, Musk-oxen, Arctic Owl, Polar Bear and Snow Foxes are some of the animals found here.
(i) Forests are very useful for us. They perform various functions. Plants release oxygen that we breathe and absorb carbon dioxide.
(ii) The roots of the plants bind the soil, thus, they control soil erosion.
(iii) Forests provide us with timber for furniture, fuel wood, fodder, medicinal plants and herbs, lac, honey, gum, etc. Forests are the natural habitat of wild life.
* Facts to Know
(i) The tropical evergreen forest in Brazil is so enormous that it is like the lungs of the earth:
(ii) Anaconda, one of the world’s largest snakes is found in the tropical rainforest. It can kill and eat a large animal such as a crocodile.
(iii) Mediterranean trees adapt themselves to dry summers with the help of their thick barks and wax coated leaves which help them reduce transpiration.
(iv) Mediterranean regions are known as ‘Orchards of the world’ for their fruit cultivation.
(v) Taiga means pure or untouched in the Russian language.
(vi) Grasslands are known by different names in different regions.
(vii) Tropical Grasslands East Africa- Savanna Brazil- Campos Venezuela- Llanos
(viii) Temperate Grasslands Argentina- Pampas N. America- Prairie S. Africa- Veld C. Asia- Steppe Australia- Down.
Name the areas of tropical evergreen forests and explain why their commercial exploitation is difficult.
These thick forests occur in the regions near the equator and close to the tropics in the Amazon baisn, Zaire basin, Malaysia, Myanmar, kampuchea, Vietnam, Indonesia. There are no pure stands of trees but all the species are intermixed which make Commercial Exploitation of these forests very difficult.
What are the local names given to temperate grasslands ?
These grasslands are known by different local names, such as Prairies in North America, Pampas in Argentina, Veld in South Africa, Steppes in Russia and Downs in Australia.
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