Question

Write short notes on any two of the following.
(a) Ecological pyramid
(b) Food web and food chain
(c) Biological or Biochemical Oxygen Demand (BOD)

Answer 1

1. Ecological pyramid is a diagram designed to show the biomass or bio productivity at each tropic level in a given ecosystem. Ecological pyramid may be upright (eg. Grassland ecosystem), inverted ( parasitic ecosystem) or dumbbell shaped ( forest ecosystem)
2. Biological oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic organism to break down organic material present in given water sample at specific temperature. BOD is also biological indicators of water pollution level that is higher demand of BOD means high level of dissolved organic chemical present and vice versa.