(a) What is “population” according to you as a biology student ?
(b)“The size of a population for any species is not a static parameter.” Justify the statement with specific reference to fluctuations in the population density of a region in a given period of time.

OR

(a) What is hydrarch succession?
(b) Compare the pioneer species and climax communities of hydrarch and xerarch succession respectively.
(c) List the factors upon which the type of invading pioneer species depend in secondary hydrarch succession. Why is the rate of this succession faster than that of primary succession ?

a) Population is collection of same species that live together in a region.
b) The stability of population is dependent on availability of food, climatic conditions, predators. The size of the population is dependent on
• Natality rate: The rate at which new organisms are born
• Mortality rate: The rate at which organisms have died.
• Immigration: The population which settles in a particular population
• Migration: The population which moves from a particular population.

OR

a) The succession which develops in relatively wetter areas. The succession occurs in marshy lands, shallow lakes is called hydrach succession. In the process of this succession the hydrarch condition is converted to mesarch condition.
b)
 

c) Factors upon which the type of invading pioneer species depend in secondary hydrarch succession are:
• Water availability
• Condition of soil texture
• Presence of seeds and propagules
• Environment
During primary succession, soil was formed so that biotic community can be established. So, secondary succession is faster than primary succession.