Life on the Earth

  • Question 61
    CBSEENGE11011109

    Describe major ecosystems of the earth.

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

    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.

    Question 62
    CBSEENGE11011110

    Describe the factors which influence the terrestrial ecosystem.

    Solution
    Ecosystems which prevail on the land are called terrestrial ecosystems. 

    Factors which affect the terrestrial ecosystems are: 

    i. 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.

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

    iii. 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.

    iv. 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.

    v. 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.

    Question 63
    CBSEENGE11011111

    Mention the important characteristics of any three forest biomes of the world.

    Solution

    The characteristics are mentioned below: 
    a. Characteristics of Tropical Forests: There are of two types Tropical Rainforests.

    i. Tropical Rainforests: 

    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.

    ii. 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.
    b. 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
    c. 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.

    Question 64
    CBSEENGE11011112

    Plants which occur in distinct groups of communities in areas having similar climatic conditions constitute:
    • Biomes
    • Trophies
    • Ecosystem
    • None

    Solution

    A.

    Biomes

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