Question

Should we be worried about low genetic variation in small populations of endangered species? Focus your answer in at least two different endangered species

Answer 1

Genetic variation is defined as the differences in DNA sequences between individuals within a population. Even though individuals of a species have similar characteristics, they are rarely identical this is due to subtle differences in their DNA. It plays a very important role in the evolution of organisms. Without genetic variation, a population cannot evolve in response to changing environmental variables and may face an increased risk of extinction. Differences in disease susceptibility and the ability to reproduce are highly influenced by genetic variation for example, if a population is exposed to a new disease, then natural selection will be based on the genes for resistance to the disease in the population. If the right genetic variation is not present then population will not be able to evolve and could be wiped out by the disease.

Population size plays a major role in this process as this variation is a result of accumulation of mutations for over many generations. As a population size dwindles, as is case of endangered species-it loses its genetic variation — and even if the species rebounds, its level of genetic variation will not. As a result endangered species with low genetic variation may risk extinction long after its population size has recovered.

CHEETAHS: More than 12,000 years ago cheetahs survived a population collapse that led to inbreeding and a loss of genetic diversity. As a result, modern cheetahs are more prone to disease and also have poor sperm quality. Cheetah males displayed a 10-fold reduction in sperm count and an elevated incidence of malformed spermatozoa (example super large heads, tiny heads, coiled or bent tails) which have served as indicators of sterility. Cheetahs displayed 90–99% less overall diversity than other cats and most other mammals.

KOALA: The genetic diversity of koalas is also low in modern populations. The low variation may be responsible for the widespread inability of the koala to resist diseases such as Chlamydia and koala retrovirus (KoRV).