(a) Following are the responses of different animals to various abiotic factors. Describe each one with the help of an example.
(i) Regulate
(ii) Conform
(iii) Migrate
(iv) Suspend
(b) If 8 individuals in a population of 80 butterflies die in a week, calculate the death rate of population of butterflies during that period.

OR

(a) What is a trophic level in an ecosystem? What is ‘standing crop’ with reference to it?
(b) Explain the role of the ‘first trophic level’ in an ecosystem.
(c) How is the detritus food chain connected with the grazing food chain in a natural ecosystem?

(a) (i) Regulate is the mechanism used by few organisms like mammals and birds to maintain homeostasis (constant body temperature, constant osmotic concentration) by physiological means.
(ii) Most organisms cannot maintain constant body temperature and have fluctuating body temperatures. The osmotic concentration of the body fluids changes with water concentration, and those plants and organisms are called conformers.
(iii) Some organism travel far away from their home when the conditions area unfavourable and return back when the conditions become favourable. E.g., birds from Siberia come to Rajasthan during winter season.
(iv) Some organisms adapt different mechanisms to escape the harsh environment outside. E.g., bacteria, fungi and few lower plants produce spores to survive unfavourable condition and to germinate when the conditions are suitable.

(b) Death rate = Number of deaths/Total populations
Death rate = 8/80=0.1 butterflies per week.

OR

(a) Organisms occupy a place in the natural surroundings or in a community according to their feeding relationship with other organisms. The level which they occupy based on their nutrition is called trophic level. Each trophic level has a certain mass of living material at a particular time called as the standing crop. The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area.
(b) Autotrophs occupy the first trophic level in the food chains. Autotrophs are producers which convert solar energy into food.
(c) The detritus food chain connected with the grazing food chain in a natural ecosystem gets foods from the remains of the grazing food chain as they are indirectly dependent on autotrophs for organic components.