B) Oxygen may not have been able to accumulate in the atmosphere
Answer:
Genetic drift
Explanation:
Genetic drift is defined as the random change in allelic frequencies from one generation to the other.
Genetic drift is an evolutionary mechanism in which the allelic frequencies in a population change through many generations. Its effects are harder in a small-sized population, meaning that this effect is inversely proportional to the population size. Genetic drift results in some alleles loss, even those that are beneficial for the population, and the fixation of some other alleles by an increase in their frequencies. The final consequence is to <u>randomly</u> fixate one of the alleles. Low-frequency alleles are the most likely to be lost. Genetic drift results in a loss of genetic variability within a population.
Genetic drift has important effects on a population when this last one reduces its size dramatically because of a disaster -bottleneck effect- or because of a population split -founder effect-.
The outer skeleton provides protection due to the fact that invertebrates do not have backbones
Endangered species are going to be extinct if they don't get help. An endangered species is considered to be in more immediate danger of extinction than a threatened species. Threatened animals are considered at risk...
"Nucleus" (Genetic Material in it) <span>directs and controls a animal cell activities
Hope this helps!</span>
