A mutation of DNA by the addition or removal of a single nitrogen-containing base is known as a mutation which shifts the rest of the DNA sequence. A) substitution
B) Crossing over
C) Inversion
D) Frameshift

mammal

explanation:

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.