Answer:
Genetic drift (sampling error)
Explanation:
According to the given information, the population under study has a small size and is more likely to be affected by genetic drift. Genetic drift refers to any chance event that leads to random changes in the allele frequencies of a population over time.
It may occur by sampling error that either makes the allele frequency 100% in the population or completely removes it from the population. Sampling error occurs quickly in the small population. The initial frequency of "blood type A" was 3/85= 0.035. Over the time period of 45 years, sampling error during gamete formation and random fertilization removed all the individuals with "blood type A" from the population and reduced its frequency to 0.
The pelagic zone can be contrasted with the benthic and demersal zones at the bottom of the sea. The benthic zone is the ecological region at the very bottom of the sea. It includes the sediment surface and some subsurface layers. Marine organisms living in this zone, such as clams and crabs, are called benthos.
