$A$ biologist studied the population of rats in a barn. He found that the average natality was $250$, average mortality $240$, immigration $20$ and emigration $30$. The net increase in population is

Scientific study of human population is called

$A$ population is correctly defined as having which of the following characteristics?
$(A)$ Inhabiting the same geographical area
$(B)$ Individuals belonging to the same species
$(C)$ Possessing a constant and uniform density and dispersion

Read the following statements and select the correct option with respect to population attributes:
$(a)$ Population density is necessarily measured in numbers.
$(b)$ Tiger census is often based on pug marks and fecal pellets.
$(c)$ Biomass is not a meaningful measure to know population size.
$(d)$ Size of a population for any species is not a static parameter.

If $4$ individuals in a laboratory population of $40$ fruitflies died during a specified time interval (i.e.,a week),the death rate in the population during that period is

What is formed by the aggregation of individual organisms of the same species?