Quiz 4 Phenotypic Evolution

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).

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

B  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.

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

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

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

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 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.

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

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

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

C  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.

A  They all describe allele frequncies.

B  They are al different components of fitness.

C  They all describe imminent extinction.

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

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

C  In that case differential selection occurs.

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  Unnatural selection as small individuals usually have the best survival.

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

C  Directional selection towards larger beak size

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

B  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).

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.