Question

What is symbiosis? Explain with an example.

Answer 1

Symbiosis

1. It is an association between two organisms in which both the organisms mutually benefit from the relationship.
2. The organisms which live in a symbiotic relationship are called symbionts.

Examples of symbionts are:

1. Lichens :
   1. Lichens provide an excellent example of symbiotic association between organisms.
   2. The body of a lichen is made up of an alga, a fungus and at times even a photosynthesising bacterium. All these organisms mutually benefit each other.
   3. The alga containing chlorophyll is capable of producing food by photosynthesis. It shares the food with the fungus, which in turn provides water and minerals to the alga.
2. Nitrogen-fixing bacteria and leguminous plants:
   1. Another example of symbiosis is between nitrogen-fixing bacteria and leguminous plants.
   2. Plants cannot use the nitrogen gas present in the air directly. Gaseous nitrogen is converted to usable nitrates during a process called nitrogen fixation.
   3. Certain nitrogen-fixing bacteria called Rhizobium live in the root nodules of leguminous plants such as pea in a symbiotic relationship. The pea plant provides food and shelter to the bacteria. In return, the bacterium fixes atmospheric nitrogen and provides nitrates to the plant to grow.