(a) What is an ecological pyramid ? Compare the pyramids of energy , biomass and numbers.
(b) Write any two limitations of ecological pyramids.

Explanation

(a) Ecological Pyramid : See Q. 28 (a)., Set -II , Outside Delhi , 2012. Graphical representation of the relationalship among the organosms at different trophilc level.
(i) Pyramid of Energy : An energy pyramid more accurately reflects the law of thermodynamics , with loss of energy being depicted at each treansfer to another trophic level, hence the payramid is always right.
(ii) Pyramid of biomass represents the total dry weight of living beings of different species at each trophic level at a particular time . in some aquatic ecosystem , like large lakes and oceans , the pyramid of biomass , sometimes assumes an inverted form.
(iii) Pyramid Numbers : A graphical representation of the total number of individuals of different species belonging to each trophic level in an ecosystem is known as pyramid of numbers. for most ecosystems like grassland ecosystem , pyramid of numbers are upright because numbering of organisms decreaces at succesively higher trophic level.
(b) Limitations : (i) It does not accommodate the food web and does not take into account the same species belonging to two or more trophic levels .
(ii) Saprophytes are not given any place.