Answer:
endocytosis
Explanation:
Endocytosis is a cellular process in which substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested material.
In DNA, the "rungs" between the two strands of DNA are formed from the nitrogenous bases adenine, thymine, guanine and cytosine
I think the third one is the answer
Answer:
Increased genetic variation reduces the species chances of being extinct. Conversely, reduced genetic variation in a species increase the chances of the species being extinct.
Explanation:
With increased genetic variation in a species, there is increased phenotypic variation amongst organisms in the species for natural selection to act on with selection pressures exerted upon the species in their environment e.g. predation or diseases. Hence even if a certain genotype express susceptibility to a certain disease, only some organisms will be selected against and there are sufficient organism without this genotype that will be able to survive and ensure the continuity of the species.
Conversely, if all the organisms express the same genotype susceptible to the disease (in extreme cases), upon exposure to the disease (which acts as the selection pressure), all the organisms will die and there will be no surviving organisms for the continuity of the species. Hence with minimal genetic variation, the species is more prone to extinction due to the inability to withstand selection pressures.
This is often a common cause of concern in the conservation of endangered species. Due to the small number of e.g. tigers remaining, most offsprings are produced through inbreeding between family members thus even though the family tree of the species is expanding, there is little genetic variation within the species. Therefore, the chances of extinction of these endangered species is high and thus biologists and conservationists have to monitor the selection pressures exerted upon these species by their environment to reduce the risk of extinction.
