It is called THERAPEUTIC INDEX. Therapeutic index is the comparison of the amount of a particular drug that causes the desired therapeutic effects and the amount that causes toxicity. The index can be low or high. A drug with a low therapeutic index will require only a small increase in dose to produce toxic effects in users.
What this student is doing is collecting data. So, he wants to check how many life forms there are in the waters nearby. In order to do so, he has to take a sample, and look at it through a microscope so as to determine the number. So, he collected a sample which is his data. He is not drawing conclusions yet, but rather counting these organisms. He is not making a peer review - his peers aren't even mentioned here. He is not forming a hypothesis because he is just counting at this point.
The fossil record essentially keeps track of the abundance and appearance of various fossils during different time periods. As time goes on, the fossils change. Using the fossil record, we can compare and contrast the fossils to develop theories about changing life forms and their connection to time.
Hope this helped :)
Although there is no context for this question, it would be safe to say that that population would have reached its carrying capacity, if not become overpopulated.
