The fluid link between the external and internal environment is

the endomembrane system i think

population. population is the number of people or animals in a particular place. an example of population is over eight million people living in new york city.

here is your answer hope i .

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.