Life on the Earth

  • Question 21

    What are algae? Mention their common characteristics and types.

    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 asexually by zoospores and sexually by gametes.
    Question 22

    What is species diversity ?

    The variation in the physical features of species.
    Question 23

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

    They are Lithosphere, Atmosphere and Hydrosphere.
    Question 24

    On what criteria the classification of kingdoms is done ?

    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.

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