Info

(a)

Perils of Small Populations

The rapidly growing human population has caused extreme reductions in the populations of some other species and subspecies. For example, only about 200 Siberian tigers remain in the wild because of hunting and habitat destruction. Even greater reductions have been experienced by the California condor, which was once found throughout the southwestern United States. In the 1980s, the condor's wild population had been reduced to nine individuals, although recovery efforts have since increased the numbers.

Small populations, such as the cheetahs shown in Figure 19-11a, are particularly vulnerable to extinction. Environmental disturbances, such as storms, fires, floods, or disease outbreaks, can kill off the entire population or leave too few individuals to maintain the population. Also, the members of a small population may be descended from only a few individuals, increasing the likelihood of inbreeding, or mating with relatives. Inbreeding in small populations often leads to decreased genetic variability, as shown in Figure 19-11b. Over evolutionary time, populations with low variability are less likely to adapt to changing environmental conditions.

figure 19-11

The genetic diversity of cheetahs (a) is so low that biologists think the cheetah population may have been reduced to a very small size in the past. Such a reduction is called a genetic bottleneck, illustrated in (b). The diagram shows how the genetic variation in a population can be reduced when the size of that population is reduced.

figure 19-11

The genetic diversity of cheetahs (a) is so low that biologists think the cheetah population may have been reduced to a very small size in the past. Such a reduction is called a genetic bottleneck, illustrated in (b). The diagram shows how the genetic variation in a population can be reduced when the size of that population is reduced.

Sirens Sleep Solution

Sirens Sleep Solution

Discover How To Sleep In Peace And Harmony In A World Full Of Uncertainty And Dramatically Improve Your Quality Of Life Today! Finally You Can Fully Equip Yourself With These “Must Have” Tools For Achieving Peace And Calmness And Live A Life Of Comfort That You Deserve!

Get My Free Ebook


Post a comment