Population size and density are the two most important statistics scientists use to describe and understand populations. A population's size refers to the number of individuals (N) it comprises. Its density is the number of individuals within a given area or volume. These data allow scientists to model the fluctuations of a population over time.
Answer:
All living things are able to respond to stimuli in the external environment.
Explanation:
All living things are able to respond to stimuli in the external environment. For example, living things respond to changes in light, heat, sound, and chemical and mechanical contact. To detect stimuli, organisms have means for receiving information, such as eyes, ears, and taste buds.
The Muscle that encircles the eye is the <span>iris </span>sphincter muscle.
B. Harder for a cell to move materials in and out of a cell
