Chapter 15: Evolution on a Small Scale Flashcards
What are the pre-zygotic reproductive barriers? Explain.
Habitat- species occupy different habitats.
Behavioral- species have different courtship behaviors.
Gametic- gametes are not compatible enough for fertilization.
Temporal- species breed at different times.
Mechanical- reproductive organs are not compatible.
What are the post-zygotic reproductive barriers? Explain.
Reduced hybrid viability- formed zygotes die before birth.
Reduced hybrid fertility- hybrids are born, but are sterile.
Hybrid (f2) breakdown- hybrids survive and are fertile, but the offspring of hybrids are less fit.
Give an example of the five pre-zygotic reproductive barriers.
Habitat- two species of garter snake in the genus thamnophis: one species lives mainly in the water, the other lives mainly on land.
Behavioral- female fireflies only flash after first being flashed by males with a species-specific pattern.
Gametic- female reproductive tract may be inhospitable or the egg may have recognition proteins on the surface.
Temporal- eastern and western spotted skunks have overlapping ranges. Eastern breeds in late winter, western breed in late summer.
Mechanical- species of many closely related insects have copulatory organs that do not match.
Explain how hybrid breakdown maintains separate species even if fertilization occurs.
If species are similar enough, fertilization may occur to reproduce offspring. Although genetically similar to both parents, the offspring would likely be infertile, and have a different number of chromosomes.
Define allopatric speciation. Describe the mechanism that may lead to genetic differences and isolation gene pools.
Allopatric means “of a separate area”. Allopatric speciation occurs when a species is geographically isolated long enough that species diverge in physical traits. When enough time has passed the species will become too different to mate.
Explain how sexual selection has led to sympatric adaptive radiation in the cichlids of Lake Victoria. Explain how the process of speciation may be reversing due to pollution in this lake.
Sexual selection can lead to sympatric adaptive radiation if a population’s mating cycle is controlled by behaviors, or other mechanisms, until species diverge. When habitats become polluted, reproductive barriers (such as behavioral) can be voided. This allows the species to reproduce.
List AND describe the three forms of selection providing an example (real or made up) for each.
Directional- mosquitos resistant to DDT.
Stabilizing- Swiss starlings lay 4-5 eggs because this the highest survival rate for young.
Disruptive- in fields, thrushes eat the snails with dark shells that lack light bands. In forests, thrushes feed mainly on snails with light-banded shells.
True or false; dominant genes always occur more frequently in a population than recessive genes do.
False.
True or false; an insect that exhibits resistance to a pesticide inherited genes that made it resistant to the pesticide.
True.
Describe in detail why the most “fit” individuals in a population become more prevalent.
The most “fit” individuals in a population become most prevalent, because they possess genes that are favorable in their environment. Additionally, since these individuals are more likely to survive, they are also more likely to pass on their traits to offspring.
True or false; members of the same population would be expected to share the same gene pool.
True.
What are the five causes of microevolution? Explain each.
Mutation- ultimate source for allele differences.
Gene flow- movement of alleles among populations by migration of breeding individuals.
Nonrandom mating- selection of mate according to genotype or phenotype. (Not chance)
Genetic drift- changes in the allele frequencies of a gene pool due to chance.
Natural selection- populations can change over generations if individuals that possess certain heritable traits produce more offspring.
