Answer:
Population studies look at factors for one individual species.
Step-by-step explanation:
In a garden, there are multiple species of plants growing. You could study different factors of each population, which is just all the individuals of one species in an area. For example, you could study how adding fertilizer affects the growth of tomato plants. To do this, you would have some tomato plants in the garden that have fertilizer added to the soil and some that don't. At the end of a certain period of time, maybe a month, measure the plants, find the average height and compare their growth. This is just one example, but there are lots of different things you could study.