Chapter 21 - Speciation, natural selection

Which scenario(s) depict allopatric speciation in process? Select all that apply. A small portion of the population on the mainland moves to an island. Over time, the island population genetically diverges from the mainland population. Two individuals from different plant species in the same geographic location mate to create a hybrid species that cannot mate with individuals from either of the parent populations. A mutation appears in several individuals of a population that prevents these members from mating with individuals that lack the mutation. Humans set up a dam in the middle of a river, splitting a fish population in two. The two resulting fish populations accumulate different sets of mutations over time.

A small portion of the population on the mainland moves to an island. Over time, the island population genetically diverges from the mainland population. Humans set up a dam in the middle of a river, splitting a fish population in two. The two resulting fish populations accumulate different sets of mutations over time.

Which phrase best describes how natural selection results in evolution? Weak individuals are eliminated by strong individuals. Individuals adapt to their environment by undergoing mutations. Individuals with particular traits leave behind more offspring than individuals with other traits. Individuals with particular traits survive better than individuals with other traits.

Individuals with particular traits leave behind more offspring than individuals with other traits.

Neutral mutations can decrease in frequency to a minimum of what percentage of the population? 25% 50% 5% 10% 0%

0%

Neutral mutations can increase in frequency to a maximum of what percentage of the population? 99% 100% 50% 75% 25%

100%

Seven species of snapping shrimp are found on either side of the Isthmus of Panama. What data provides good evidence that this is speciation by vicariance? That populations on opposite sides of the Isthmus are reproductively incompatible. The DNA of each current species is most similar to that of a species found on the opposite side of the current Isthmus. That it takes about 3 million years for accumulation of enough mutations to result in new species of snapping shrimp. The rate of evolution can be calculated because the populations have been separated for about 3 million years.

The DNA of each current species is most similar to that of a species found on the opposite side of the current Isthmus.

A good example of vicariance is a: rise in sea level floods a coastal area and breaks it up into several small islands distant from each other. change in allele frequencies in two closely related populations that are isolated from each other by a geographic barrier.

change in allele frequencies in two closely related populations that are isolated from each other by a geographic barrier.

A deleterious mutation: increases survival and/or reproduction. decreases survival and/or reproduction. does not affect survival or reproduction.

decreases survival and/or reproduction.

Over time, in a population, new mutations of a given gene may: disappear from the population. remain at relatively low levels in the population. disappear, remain at low levels, or become fixed. become fixed as the only form of the gene in the population.

disappear, remain at low levels, or become fixed.

Speciation has occurred when: organisms from a single species are separated by a physical barrier. a DNA sequence is changed, resulting in an altered protein product. divergent populations evolve to the point where interbreeding does not produce viable, fertile offspring. mutations in a population reach 100% of the organisms in that population. an alteration in an organism's genetic material becomes permanent.

divergent populations evolve to the point where interbreeding does not produce viable, fertile offspring.

A neutral mutation is one that: increases survival and/or reproduction. decreases survival and/or reproduction. does not affect survival or reproduction.

does not affect survival or reproduction.

Evidence indicates that a number of finches from Ecuador dispersed to the Galapagos Islands more than 300 miles away and ultimately gave rise to the different species of Galapagos finches that exist today. This is good evidence of speciation by vicariance. true false

false

Once a mutation is introduced into a population, it will eventually be passed on until it is found in 100% of the individuals in that population. true false

false

When individuals of a parent species are separated geographically, one population of separated individuals is more likely to acquire neutral mutations than the other. false true

false

If the frequency of the blue trait changes randomly in the population from generation to generation, the most likely cause for this is: epigenetic inheritance. mutation. genetic drift. natural or artificial selection.

genetic drift.

A geologic barrier betwen two populations of one species can contribute to speciation because of: similar environmental conditions in the two locations. increased mutation rates due to separation. lack of gene flow between populations.

lack of gene flow between populations.

Which type of mutation does not undergo natural selection in a population? deleterious neutral beneficial

neutral

In animals with alleles for a given trait of A and a, if Hardy-Weinberg conditions are met, which one of the choices is not a possible genotype frequency? q2 Each of the genotype frequencies provided is a possibility. p2q2 2pq p2

p2q2

In order for the gene pools of two closely related species to remain distinct, there must be: different selection pressures on each species. a geographic barrier between them. some form of reproductive isolation. different mutation rates in each species.

some form of reproductive isolation.

Which of the factors would be least likely to affect the mutation rate in a population? generation time of the species the level of recombination in a population the presence of mutagens in the environment age of the males reproducing in a sexual population

the level of recombination in a population

An allele that has acquired a mutation at a particular nucleotide position is just as likely to acquire a subsequent mutation as an allele which has not been previously mutated. true false

true

If the environmental conditions change, a neutral mutation can become advantageous or disadvantageous. false true

true

Speciation is said to occur when: two populations become permanently physically separated from each other. two populations become completely reproductively isolated from one another. partial reproductive isolation between two populations is achieved. any two mutations become fixed differences between the populations. all deleterious mutations have beeneliminated from the populations.

two populations become completely reproductively isolated from one another.

Speciation occurs when: partial reproductive isolation between two populations is achieved. two populations become reproductively isolated from one another. two populations become physically separated from each other. all deleterious mutations have been eliminated from two populations. any two mutations become fixed differences between two populations.

two populations become reproductively isolated from one another.

Indicate whether genetic drift, if it acted alone, could cause changes in the allele frequency of a population. Acting alone could not change allele frequency. Acting alone could change allele frequency.

Acting alone could change allele frequency.

Indicate whether natural selection, if it acted alone, could cause changes in the allele frequency of a population. Acting alone could change allele frequency. Acting alone could not change allele frequency.

Acting alone could change allele frequency.

Vicariance is defined as: variation in frequency of mutations among different genes in a population. variation in allele frequencies within a population of organisms. migration to a distant, isolated island resulting in isolated populations. when a geographic barrier arises that isolates two populations.

when a geographic barrier arises that isolates two populations.