Final answer:
The population in this study refers to the group of tomato plants being studied. The biologist will compare the plants that received the fertilizer to those that did not.
Step-by-step explanation:
The population in this study refers to the group of tomato plants that are being studied by the biologist. It represents all the tomato plants that are subjected to the new fertilizer. To determine the effect of the fertilizer, the biologist would compare the characteristics and growth of the plants that received the fertilizer to those that did not.