A.   True, but in reality there are often several additive alleles that create further variation, and most of all: environmental variance can smooth out the distribution, so many in-between body sizes are found in the population (with varying frequencies).

B.   Yes, that is the universal rule, if one gene locus determines a phenotypic trait, then there are no “In-between” sizes.

C.   That’s a theoretical assumption, but in nature there are always 4 pairs of alleles that code each phenotypic trait. This is a safeguard against mutations, as a mutation will not have any effect on the phenotype this way.

A.   Directional selection towards larger beak size

B.   Galapagos selection, as this phenomenon is not found elsewhere.

C.   Unnatural selection as small individuals usually have the best survival.

A.   The convergence upon a specific phentoypic trait value is characteristic for stabilizing selection.

B.   This would be typical for reverse selection.

C.   Whenever individuals in a population die, we speak of disruptive selection

A.   There would be either directional or disruptive selection acting on the populations.

B.   If there is no change, there is no selection acting upon that trait.

C.   In that case differential selection occurs.

A.   They all describe imminent extinction.

B.   They all describe allele frequncies.

C.   They are al different components of fitness.

A.   A small population is more nimble to adapt to quick environmental change, like for example the small polar bear populations.

B.   Slow change and a large population size allow enough variation and time for new mutations to occur, and also not enough time for beneficial alleles to spread in the population through many generations.

C.   Only the speed of the environmental change matters, no other factors such as population size.

A.   Standing genetic variation means that all individuals are already pre-adapted to the future and there is no need for further selection.

B.   Standing genetic variation is not promoting evolution, as change is the most important aspect of it (not standing still).

C.   Standing variation is the variation already present in a population, so there might be many, many indviduals able to survive the new environmental conditions, and their survival assures the survival of their species.

A.   Among many measures, one consideration is to assure the population has a large gene-pool by enabling migrations and relocations to preventing isolation. That increases the standing genetic variation, and perhaps population size.

B.   By putting a handful of endangered animals in a Zoo, or freeze them to preserve some of their genetic material.

C.   We can't: Natural selection is already nature’s best mechanism for survival of a species.

A.   A situation where a species cannot adapt to changing environmental conditions, due to e.g. a lack of genetic variation (only giraffes with short necks present), trade-offs (can’t become lighter and stronger), or correlated traits.

B.   A situation where one species can adapt to a changing environment, but constraints all other species (Tyrannosaurus rex).

C.   A geologic feature that does not allow migration of species from one continent to another.

A.   Variation in phenotypes (color, shape, behaviour, etc) that does not require genetic adaptation, as it is a response to the environment.

B.   Phenotypic plasticity is the same as standing genetic variation.

C.   The change of a trait from one generation to another (mutation).