Scientific study of human population is called

Which of the following attributes is/are of a population but not of an individual organism?

The basic unit of animal population which is communal interbreeding,in a species is known as

The rate of natural increase in human population refers to

The average population density on Earth is approximately:

If $10$ individuals in a laboratory population of $50$ fruit flies die during a week, then the death rate during this period is $= ........$ individuals per fruit fly per week.