Prokaryotes differ from eukaryotes because:

a. they do not have a nucleus
b. they do not produce rna
c. they have a plasma membrane
d. they are single-celled

The answer is A. They do not have a nucleus surrunding their DNA.

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.