Which of the following favors one phenotypic extreme over another causing a shift in the phenotypic mean?
Directional selection
What happens to the distribution of phenotypes in directional selection?
In directional selection, a population’s genetic variance shifts toward a new phenotype when exposed to environmental changes. In diversifying or disruptive selection, average or intermediate phenotypes are often less fit than either extreme phenotype and are unlikely to feature prominently in a population.
How might overfishing of a large pink salmon select for smaller body size in subsequent generations?
How might overfishing of large pink salmon select for smaller body size in subsequent generations? Smaller fish may be able to survive longer and reproduce more often than larger fish. Over generations, smaller adult salmon could become more common in the population. This is called directional selection.
What is distribution of traits?
In terms of phenotypes, describe what is meant by the phrase, “distribution of traits.” This occurs when males display certain traits that attract the female, such as peacocks fanning out tails.
What are two ways that genetic drift can occur quizlet?
The organism that reproduces in the neighboring population is adding a new allele to the gene pool. Name two processes through which genetic drift can occur….
- Genetic drift. – allele frequencies change due to chance.
- Gene flow.
- Mutation.
- Sexual selection.
- Natural selection.
What could cause genetic drift to occur within a population quizlet?
Chance events such as a natural disasters can cause genetic drift. For example, if the only white rabbits in a population get killed by a storm, the allele for white fur will diminish or disappear in the population.
What could cause genetic drift to occur within a population?
Random drift is caused by recurring small population sizes, severe reductions in population size called “bottlenecks” and founder events where a new population starts from a small number of individuals. Genetic drift leads to fixation of alleles or genotypes in populations.
In which populations does genetic drift most often occur quizlet?
Physical movement of alleles from one population to another. Change in alleles frequencies due to chance alone, occurring most commonly in small populations. Genetic drift that occurs after a small number of individuals colonize a new area.
Is genetic drift problematic?
In Bacteria, assessing the contribution of genetic drift to genome evolution is problematic because the usual methods, based on intraspecific polymorphisms, can be thwarted by difficulties in delineating species’ boundaries.
Why does genetic drift have more of an impact on the evolution of small populations than large ones quizlet?
Genetic drift is more likely to cause evolution in a small population than in a large one because: with fewer individuals, which individuals mate can have larger effects in small populations. Suppose a neutral allele arises in a LARGE population of organisms.
What does it mean when an allele has become fixed or fixation has occurred?
A fixed allele is homozygous for all members of the population. The term allele normally refers to one variant gene out of several possible for a particular locus in the DNA. When all but one allele go extinct and only one remains, that allele is said to be fixed.
Is genetic drift more influential in small or large populations?
Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error). Genetic drift occurs in all populations of non-infinite size, but its effects are strongest in small populations.
What can prevent gene flow?
Because gene flow can be facilitated by physical proximity of the populations, gene flow can be restricted by physical barriers separating the populations. Incompatible reproductive behaviors between the individuals of the populations also prevent gene flow.