Ans. Soil erosion and depletion are the major threats to soil as a resource. Both human and natural factors can lead to degradation of soils. Factors which lead to soil degradation are deforestation, overgrazing, overuse of chemical feritilisers or pesticides, rain wash, landslides and floods.
Tropical Evergreen Forests
Evergreen forests do not shed their leaves simultaneously in any season of the year.
Deciduous forests shed their leaves in a particular season to conserve loss of moisture through transpiration.
Ans. Two steps that government has taken to conserve plants and animals are:
i. It has set up national parks, wildlife sanctuaries and biosphere reserves to protect our natural vegetation and wildlife.
ii. It has banned the killing of lions, tigers, deers, great Indian bustards and peacocks.
Ans. Ways to conserve water
i. Rain water harvesting.
ii. The canals should be properly lined to minimise losses by water seepage.
iii. In dry regions with high rates of evaporation, drip or trickle irrigation is very useful.
Ans. Fresh water accounts for only about 2.7 per cent. Nearly 70 per cent of this occurs as ice sheets and glaciers in Antarctica, Greenland and mountain regions. Due to their location they are inaccessible. Only 1 per cent of freshwater is available and fit for human use. It is found as ground water, as surface water in rivers and lakes and as water vapour in the atmosphere.
Ans. CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) is an international agreement between governments. It aims to ensure that international trade in specimens of wild animals and plants does not threaten their survival. Roughly 5,000 species of animals and 28,000 species of plants are protected. Bears, dolphins, cacti, corals, orchids and aloes are some examples.
Ans. The uneven distribution of population in different parts of the world is mainly due to varied characteristics of land and climate. The rugged topography, steep slopes of the mountains, low-lying areas susceptible to water logging, desert areas, and thick forested areas are normally sparsely populated or uninhabited. Plains and river valleys offer suitable land for agriculture. Hence, these are the densely populated areas of the world.
Ans. In areas of heavy rainfall, huge trees may thrive. The forests are thus associated with areas having abundant water supply. As the amount of moisture decreases the size of trees and their density reduces. In the regions of moderate rainfall short stunted trees and grasses grow forming the grasslands of the world. In dry areas of low rainfall, thorny shrubs and scrubs grow. In such areas plants have deep roots and leaves have thorny and waxy surface to reduce loss of moisture by transpiration.
Ans. Wildlife is important to us because
i. They provide us milk, meat, hides and wool.
ii. Insects like bees provide us honey, help in pollination of flowers and have an important role to play as decomposers in the ecosystem.
iii. The birds feed on insects and act as decomposers as well.
iv. Vulture due to its ability to feed on dead livestock is a scavenger and considered a vital cleanser of the environment.
Ans. Factors affecting soil formation are:
Parent Rock - Determines colour, texture, chemical properties mineral, content, permeability of soil.
Climate – Temperature and rainfall influence rate of weathering and humus.
Relief - Altitude and slope, determine accumulation of soil.
Flora, Fauna and Micro-organism - Affect the rate of humus formation.
Time - Determines thickness of soil profile.
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