Crossword puzzle clue "study of populations"

relating to demography, also DEMOGRAPHICAL

the study of population statistics and trends, such as births, deaths, and disease

to pack tightly

NERD, a person obsessed with computers at the expense of human interaction, also NURD

BIOTA, (Greek) the flora and fauna of a region

ECOTYPE, a group of organisms which have adapted to a particular environment and so have become different from other groups within the species