AP Biology Unit 7: Natural Selection Review

How does genetic drift usually affect a population?

• Usually it increases the size of a population

• Usually it increases the selective pressures on a population

• Usually it decreases the genetic variation of the population

• Usually it introduces new genes into a population

How is background extinction rate used to determine if a mass extinction is happening?

• Comparing the background rate to the current rate

• The background extinction rate is the level of extinctions that occurs during a mass extinction

• Dividing background rate by historical rate

• Comparing the background rate to the rate of extinctions during the most recent mass extinction

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What are the two types of genetic drift commonly seen?

• Temporal isolation and hybrid sterility

• Disruptive selection and convergent evolution

• Founder effect and bottleneck effect

• Gene flow and artificial selection

What does background extinction rate mean?

• The total number of extinctions that have occurred in Earth's history

• How many organisms are going extinct without us knowing

• The average number of extinctions observed in the fossil record during periods of stability

• How many extinctions are currently happening

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NGSS.HS-LS4-5

What is the bottleneck effect?

• When survivors of a natural disaster repopulate the area

• When selective pressures change and new traits become the most fit for an area.

• When members of one population migrate to another population

• When new organisms migrate to an area and start a new population

What factors would increase the frequency of a genotype in a population over time?

• Increased reproduction rates in a population

• Selective pressures that make the trait favorable

• Genetic drift

• Mutations in the population

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Why would the presence of a particular genotype or phenotype decrease in a population over time?

• Due to increased competition

• Reproductive isolation

• Changes in the environment that now make the trait less favorable

• Gene flow

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What are prezygotic barriers to reproduction?

• Any barrier that reproductively isolates species

• Barriers that prevent the production of a fertilized egg

• When the offspring of two organisms are sterile

• Barriers that prevent a zygote from developing into a viable offspring

If a recessive disorder is found to affect 1 in 500 live births, what is the frequency of the recessive allele in the population?

• 0.002

• 0.9553

• 0.9125

• 0.0447

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What is the difference between allopatric and sympatric speciation?

• Sympatric - populations are geographically separated ; Allopatric - populations live together but are reproductively isolated

• Allopatric - populations are geographically separated ; Sympatric - populations live together but are reproductively isolated

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