Correct Answer - Option 4 : Humus
The correct answer is Humus.
Microorganism
- Microorganisms are too small and are not visible to naked eyes.
- Microorganisms are found in air, water and in the bodies of plants and animals.
- They may be unicellular or multicellular.
- Microorganisms are classified into four major groups.
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Bacteria- Bacteria convert gaseous nitrogen into a usable form and release it into the soil.
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Fungi- Fungi are cosmopolitan and occur in air, water, soil and on animals and plants.
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Protozoa- protozoans are heterotrophs and live as predators or parasites.
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Algae- Algae are largely aquatic both fresh water and marine organisms.
Explanation-
- Humus is a thick brown or black substance.
- The rotting dead matter in the soil is called humus.
- The microorganisms which converts the dead animals and plants to humus are called decomposers.
- It is an important component of the soil because it contains many useful nutrients and minerals.
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Dead organic matter in the form of decaying plants and sometimes dead animals on the ground disappear after some time.
- This is because the microorganisms decompose dead organic waste of plants and animals converting them into simple substances.
- These substances are again used by other plants and animals.
Thus, Microorganisms act upon the dead plants to produce humus.
