How does the distribution of traits in a population look when displayed as a graph?
Describe three causes of genetic variation in a population.
Mutation, recombination, and random pairing of gametes
What is meant by the term human gene pool?
The total amount of genetic information with humans
How is phenotype frequency computed?
the number of indivduals with the particular phenotype divided by the
What are the conditions that a population must meet in order to have a genetic equilibrium?
No mutations, no individuals entering or leaving the population,
the population is large, individuals mate randomly, selection does not occur.
By observation only, is it easier to deduce the genotype of organisms for an allele that has complete dominance or incomplete dominance?
How does the pairing of gametes produce genotypic variation?
The smallest unit in which evolution occurs is?
Length, weight, and many other quantitative traits in a population tend to show variation
that, when plotted on a graph, looks like?
For a population to be in genetic equilibrium,
No mutations, No individuals entering or leaving the population, the population is large, Individuals mate randomly, Selection does not occur
What types of individuals in a population are represented by the two ends of a bell curve?
Individuals represented by the two ends are those with extreme variations of a specific trait.
What are the three main ways that variations in genotype arise in a population?
Variations arise through mutation, recombination during meiosis, and the random pairing of gametes during fertilization.
What five assumptions must be made for the Hardy-Weinberg genetic equilibrium to apply to a population?
(1) No net mutations occur; (2) individuals neither enter nor leave the population;
(3) the population is large; (4) individuals mate randomly; and
(5) selection does not occur.
Does a gene pool include the genes of individuals that cannot reproduce?
Explain your answer
no, because those genes are not available for the next generation
How is it that many varied but similar phenotypes occur within families?
Mutation, recombination, random pairing of gametes
Does genetic equilibrium exist in a flock of mallards?
How can immigration and emigration alter allele frequencies in a population?
Individuals enter and leave the population, resulting in gene flow
Any violation of the conditions necessary for Hardy-Weinberg equilibrium can result in
The movement of reproductive individuals from one population to another results in
Genetic drift is most likely to occur in
Assortative mating is
the selection of a mate based on similarity of traits
Starlings produce an average of five eggs in each clutch. If there are more than five, the
parents cannot adequately feed the young. If there are fewer than five, predators may
destroy the entire clutch. This is an example of
List five conditions that can disrupt genetic equilibrium and cause evolution to take place
mutations, gene flow, genetic drift, nonrandom mating, and natural selection
Explain how a Hardy-Weinberg genetic equilibrium is affected by mutations
By producing totally new alleles for a trait, mutations can change allele frequencies.
What is one potential negative consequence of nonrandom mating based on geographic proximity?
Matings with some degree of kinship may occur, increasing the chance of offspring with disorders caused by recessive genes.
How might being brightly colored increase the fitness of the males of some bird species?
The bright coloration may increase a male’s chances of being selected for mating by a female.
Why is genetic homozygosity dangerous to a nearly extinct species?
Genetic homozygosity leaves no variation for natural selection to act on. Therefore, a new disease could wipe out the entire population.
If a cow develops a preference for eating white four o’clock flowers and ignoring
pink and red four o’clock flowers, what type of selection is being demonstrated? Would the cow eventually eliminate all white four o’clock flowers from the population on which it feeds?
directional selection; the cow would not eliminate all white flowers because the allele for white flowers is also carried by plants with pink flowers, which are not eaten. Crosses between plants with pink flowers would continue to produce some plants with white
Explain the role of mutations in evolution.
Mutations can produce new alleles for the trait
Contrast gene flow with genetic drift
Genetic drift occurs due to chance, gene flow is when a population leaves the environment
Explain why genetic drift is more significant in smaller populations.
The failure of one organism can disrupt the growth of the entire population
Give an example of a species that exhibits the effects of sexual selection.
For each of the three patters of natural selection, give an example of a species that exhibits the effects of that selection.
lizard, limpets. anteaters
One limitation of the morphological species concept is that
Phenotypic differences among individuals of a single population
According to the biological species concept, a species is a population of organisms that
can interbreed but cannot breed with other groups
Fish populations that do not interbreed because they live in different ponds may evolve
into separate species due to
Bird populations that do not interbreed because they cannot recognize each other’s
mating calls may evolve into separate species due to
A pattern of rapid evolutionary changes followed by long periods of no change is
What are two limitations of the biological species concept?
A satisfactory definition is not provided for species of extinct organisms or for organisms that do not reproduce sexually.
What is one advantage of prezygotic isolation over postzygotic isolation?
Individuals do not waste gametes by producing offspring that cannot reproduce.
Describe two pieces of evidence indicating that speciation does not always occur at the same rate.
Some species of moths on the Hawaiian Islands appear to have evolved during the past thousand years, whereas speciation in other organisms may take millions of years. The fossil record shows that periods of a few thousand years during which many species appeared were separated by much longer periods during which there was little speciation
Some scientists predict that if global warming continues over the next few centuries,
melting of the polar ice caps will raise the level of the oceans, causing some peninsulas to
become islands. How might this change eventually affect the species that live on these peninsulas?
If the peninsulas become islands, the species that live there could become geographically isolated and eventually evolve into different species.
Give an example of a limitation of the morphological concept of species.
Give an example of organisms that show geographic isolation.
desert and Amargosa pupfish
Give an example of two organisms that are probably a result of allopatric speciation
White-tailed antelope squirrels and Harris's antelope squirrel
What appears to have led to the reproductive isolation of the wood frog from the leopard frog?
The times that the wood frog mate and leopard frog mate are different
What role did Ernst Mayr play in the development of the modern biological species concept?
He proposed that a species is a population of organisms that can successfully interbreed but cannot breed with other groups
Explain how geographic isolation can lead to allopatric speciation.
The populations separated by a geographic barrier no longer experience genetic flow between them, leading to allopatric speciation
Explain how reproductive isolation can lead to sympatric speciation.
Competing individuals can gain an advantage by changing to a slightly different niche
contrast the model of punctuated equilibrium with the model of gradualism
A gradualism model shows the species slowly separating, while a model of punctuated equilibrium shows sudden splits in the chain
Describe one possible scenario of postzygotic reproductive isolation in an animal species.
A horse and a donkey could mate and create a mule, which couldn't breed
How might the generation time of a population affect future speciation?
The species that reproduces more evolves faster
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