a reduction of the size of a population to single or few individuals resulting in loss of genetic variation is known as the

Bottleneck effect

Explanation:

The Bottleneck effect is when species go through an event that reduces its population. The ones that survive have reduced genetic diversity compared to the original population since fewer individuals means there are fewer genotypes.

littering streams           is the answer

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.