Studying close relatives allows behavioral geneticists to determine the effect of genes on the environment and population
Differences between individuals occur because of differences in genetic factors.
The properties possessed by each individual can be passed on to their descendants including gender, disorders/disease, or blood type
These gene differences contribute to the growth of the human population
The population influences the carrying capacity of the environment.
Carrying capacity of the environment is the ability of the environment to provide the resources it has for the life of creatures within normal limits. The resources produced or available are very limited, so if the population exceeds the limit, environmental problems will occur. These problems include the scarcity of natural resources, the emergence of pollution or the occurrence of competition in fighting over existing natural resources.