Biology for ( Grade 10 )

• As much as food web complexes are there as much
  ecosystem is permanent or stable, such type of ecosystem does not
  degenerate naturally and continues for longer time period.


• The ecosystems which have simple food webs are not
  more stable. It means that this type of food web can be finished at
  nay time. Any attack or cutting of plants can causes the destruction
  of while ecosystem e.g. Gondwana forest is converted into the
  desert by the activity of men. this is the example of desertification
  by men.
  DIFFERENCE BETWEEN FOOD CHAIN AND FOOD WEB
  Food chain Food web

1. Food chain is the straight single
   path of transfer of food energy in
   the ecosystem.


2. t consists of a number of inter –
   connected food chains through
   which food energy is passed in the
   ecosystem.


3. Members of higher trophic level
   feed upon a single type of
   organisms of lower trophic level.


4. Members of higher trophic level
   can feed as a number of alternative
   organisms of the lower trophic
   level.


5. Presence of food web increases
   the stability of the ecosystem.

15.4 ECOLOGICAL PYRAMIDS :