Is it possible for marine scientists to get an exact count of a population? why or why not?

No, that is completely impossible. The reasoning behind it is because if its a large group of fish they're swimming back and forth ect, ect, it would be like counting a bowl of rice, but not being able to take any out. To get around these counting problems, scientists take data from just a small portion of the population called a sample. They take several samples and then use the average size of those samples to calculate an estimate of the entire population size.

If you need help feel free to ask!

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

the answer is d p: cell, q: organ, r: organ system, s: tissue