Food Web and Ecological Pyramids

Food chain

The process of transfer of food and energy from one trophic level to another trophic level makes a linear chain called food chain. E.g. Plants are eaten by grasshoppers eaten by frog eaten by snake eaten by eagle.

Food web:

The network of food chains into various trophic levels is called food web.

Trophic level:

The nth position occupied an organism in its food chain is called its trophic level. E.g.

eagle (5th) ----> snake (4th) -----> Frog (3rd) -----> Grasshopper (2nd) ------> Grass (1st trophic level)

Ecological pyramid:

The graphical presentation of the relationship between the producer and various level of consumer in terms of biomass, population, energy accumulated etc. is called ecological pyramid.

Types of ecological pyramid:

• Pyramid of number: The graphical relationship between the producers and various level of consumer based on their population is called pyramid of number. This pyramid is always erect in both terrestrial and aquatic ecosystem. This pyramid is erect because the populations of producers are highest and then the number keeps on decreasing as we move up in the food chain. So tertiary consumers are least in number.

• Pyramid of biomass: The graphical representation between producers and various levels of consumers on the basis of their biomass (body weight) is called pyramid of biomass. This pyramid is erect in terrestrial and inverted in aquatic ecosystem because body mass of terrestrial food chain decreases as we go up in the food (producers have high biomass and tertiary consumers have less biomass) chain whereas biomass increases as we go up in the aquatic food chain (producers have less biomass but tertiary consumers have large biomass).

• Pyramid of energy: The graphical representation between produces and various levels of consumers on the basis of energy accumulated by them is called pyramid of energy. This pyramid is always erect in both terrestrial and aquatic ecosystems because the energy accumulated by producers by photosynthesis is not stored in their body totally as some part of the energy they produce is used to perform different activities. So the energy flow decreases from producers to top level of consumer.