Life Processes

  • Question 65

    “Animals depend on plants”. Justify the above statement.

    Animals cannot produce or make their own food. The plants on the other hand can make food by fixing solar energy in the form of chemical energy by the process of photosynthesis. This chemical energy is locked in the food molecules which are taken up by the animals. This food is oxidised by the oxygen, taken in from the atmosphere, that is also released by the plants, to give energy to the animals to do work and to grow. Thus, heterotrophic organisms such as animals are dependent on plants directly or indirectly.
    Question 66

    How do animals obtain their nutrition?


    The digestive system is different in various animals, so the food and the way nutrition is obtained differ.
    In single celled-organisms, like amoeba, the food is taken in by the entire body surface and digested with the heklp of enzymes in the food vacuole. As the complexity in the body of animals increases, different parts specialised to perform different functions like ingestion, digestion, absorption digested food and utilisation.

    Question 67

    How does nutrition take place in amoeba?


    Engulfing of Food: Amoeba obtains food by phagocytosis (a type of holozoic nutrition). Amoeba engulfs the food by forming pseudopodia.

    Two pseudopodia start growing from opposite sides of food particle from amoeba. They completely encircle the food. The membranes of both the pseudopdia dissolve at the point of touching and the food is encaptured into the Amoeba (one cell body) in a bag known as food vacuole.

    Digestion of Food: Inside the food vacuole, complex substances of the food are broken down into simpler one. The digested simple substances diffuse from food vacuole into cytoplasm.

    The remaining undigested material is moved near the surface of the single-celled body of amoeba and thrown out.

    Fig. 6.8. Engulfing of food by Amoeba

    Question 68

    How does nutrition take place in Paramoecium?

    Paramoecium is unicellular animal which has a definite shape (slipper-like).

    Paramoecium takes in food at a specific point (through oral groove to mouth to gullet). Food such as bacteria or very small organisms are move to the specific spot (ingestion point) by the movement of cilia which are present on all over the single-celled body.
    From the gullet a food vacuole is formed which start circulating in the endoplasm. During circulation food is digested by enzymes. The digested food diffuses into the cytoplasm and undigested food is thrown out through anal pore.


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