How does population density differ from population size? a. population size takes all organisms into account, while population density only takes specific age groups of the population into account. b. population size is the total number of organisms, while population density is the total number of organisms within a given area. c. population size is the total number of organisms within a given area, while population density is the total number of organisms of a specific age. d. population size is the total number of organisms of all species, while population density is the total number of organisms of a specific species.