Population density of terrestrial organisms is measured in terms of individuals per

Explain the characteristics of a population.

The process by which individuals are included into a population is known as

Members of a population:

Read the given statements carefully and select the correct ones:
$(1)$ Individuals of the same species together form a population.
$(2)$ Mortality is an important factor for population growth.
$(3)$ Natality (birth rate) is an important factor for the immediate increase in population size.
$(4)$ In commensalism,both organisms benefit from the interaction.

The type of population,where pre-reproductive animals occur in large numbers,is