Name the phenomenon being described in each of these (hypothetical) examples, and describe how it is likely to affect allele frequencies in succeeding generations.
a. $A$ beetle species is introduced to an island covered with dark basaltic rock. On this dark background, dark beetles, TT or $T t$, are much more resistant to predation than are light-colored beetles,
$t t .$ The dark beetles have a large selective advantage. Both alleles are relatively common in the group of beetles released on the new island.
b. Another beetle population, this time consisting of mostly light beetles and just a few dark beetles, is introduced onto a different island with a mixed
substrate of light sand, vegetation, and black basalt. On this island, dark beetles have only a small selective advantage.
c. $A$ coral-reef fish has two genetically determined types of male. One kind of male is much smaller than the other, and sneaks into larger males' nests to fertilize their females' eggs. When small males are rare, they have a selective advantage over large males. However, if there are too many small males, large males switch to a more aggressive strategy of nest defense, and small males lose their advantage.
d. In a tropical plant, $C C$ and $C c$ plants have red flowers and cc plants have yellow flowers. However, Cc plants have defective flower development and produce very few flowers.
e. In a species of bird, individuals with genotype $M M$ are susceptible to avian malaria, $M m$ birds are resistant to avian malaria, and $m m$ birds are resistant to avian malaria, but the $m m$ birds are also vulnerable to avian pox.