Answer;
-Birth rate
Explanation;
-The birth rate is the total number of live births per 1,000 in a population in a year or period. For example; in one year, 35 giraffes are born to a population.
-A population is defined as a group of individuals of the same species living and interbreeding within a given area. Members of a population often rely on the same resources, are subject to similar environmental constraints, and depend on the availability of other members to persist over time. Scientists study a population by examining how individuals in that population interact with each other and how the population as a whole interacts with its environment.
Accualy some do, but that's a little rare, so I'm guessing because each child gets some of there mom and dad's to genetics, one child might get some of there mom's but more of there dad's and the other might get some of there dad's and more or there mom's..? not sure if that makes any sense-
