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HETEROTROPHIC NUTRITION

1.    The mode of Nutrition in which organisms obtain food from plants or other animals is called Heterotrophic Nutrition. These organisms are called Heterotrophs.
2.    Some plants do not have chlorophyll so they cannot synthesize their food and depends on other plants or animals. Such non-green plants include fungi some bacteria and some flowering plants.
3.    Heterotrophic plants can be divided in the following types.
      (A) Parasitic Plants
      (B) Saprophytic Plants
      (C) Symbiotic Plants
      (D) Insectivorous Plants

(A)    Parasitic Plants
        Some non-green plants obtain their food from other green plants are called parasitic plants. The plant which provides food is called host plant. The parasitic plant develop special roots for absorption of food. These roots called haustoria. Haustoria                    penetrate the host tissues and reaches the vascular bundles (xlyem & phloem).
•    Parasitic Plants are of two types:-
    (a) Total parasitic plant: Completely depend on host plant for their food.
    e.g.     (i) Cuscuta or Amarbel
        (ii) Apodanthes
        (iii) Rafflesia (Largest flower in the world)
    (b) Partial parasitic plant:- These plant have green leaves and can synthesise their food but depend on host plant for water & minerals. e.g. Mistletoe, Sandalwood.

(B)    Saprophytic Plants
        These plant obtain their food from dead and decaying matter of animal and plants. E.g. Fungi (bread moulds, mushrooms, some bacteria (Bacillus vulgaris). Fungi appears as a green, white or brown coloured patches. Microscopically they show thread             like structures called hyphae. The network of hyphae is called mycellium.

 

Fungi secretes digestive juices on dead and decaying matter and convert it into a solution. Then they absorb nutrients from it in soluble forms. Fungal spores are present in the air and they germinate & grow on wet and warm things and spoil the things.
Some fungi are useful for various purposes like
In food         -     Mushrooms (Agaricus)
In Bakery    -    Yeast (Saccharomyces)
In Medicines    -    Penicillium notatum from which Ist antibiotic penicillin has been obtained.

Fungi causes diseases in plants like rust (puccinia), smut (ustilago), in wheat and ring worm in animals. Caesar mushroom or poison cup looks like mushroom but it is lethal.

(C)    Symbiotic Plants
        Mutual relationship between two organisms in which both organisms are benefitted and they share shelter and Nutrients is called Symbiosis. These organisms are called Symbionts. Certain fungi live in the roots of trees (Mycorrhizae). The plant                      provides Nutrients to the fungi and fungi help the plant to take up water and nutrients from the soil.
       Lichens are symbiotic association between algae and fungi. in which fungi provides shelter, water and minerals to the algae and algae provide food to fungi by photosynthesis. Lichens are termed as pollution indicator as they cannot survive in air                     polluted  SO2 condition.
      Leguminous plants like gram, moong, urad, peas and beans have nodules in which Rhizobium bacteria is found. This Rhizobium convert atmospheric nitrogen into nitrates for leguminous plant.

(D)    Insectivorous plants 
         Some plants can trap insects and digest them to obtain nitrogen are called Insectivorous plants. These plants are green but found in nitrogen deficient soil. So these plant trap insects and feed on to               fulfill their nitrogen requirement. These plants are  known as partial autotrophs. e.g. Pitcher plant (Nepenthes), Venus flytrap, Sundew, Bladderwort

        In pitcher plant leaf is modified into pitcher. Leaf apex forms a lid which helps in opening and closing of pitcher. Inside pitcher downwardly directed hairs are present. Which does not let an insect to                  come out.
       When insects sit on opening of pitcher, it slips down and is trapped by hairs than lid gets closed and insect is digested by digestive juice secreted by pitcher.

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