Human activity has reduced the mountain gorilla population to dangerously low levels. In the 1800s, the northern elephant seal was hunted to near extinction, but it is now making a comeback. The cheetah is an endangered species. Decreases in numbers of the northern right whale has lowered the genetic diversity of the population. Variation is entirely attributable to mutations.
Variation is due to a combination of genetic and environmental factors.
Variation has no effect on an individual's ability to survive and reproduce. Variation is due solely to the influence of the different environmental factors that an individual experiences. A population has two alternative alleles for the Q gene, Q and q. Human babies are healthiest if their birth weight is around 7 pounds. Neither p nor q change.