AP Biology Unit 2: Evolution and Natural Selection — Questions and Answers

107 in-depth question-and-answer cards from Schoology Unit 2 evolution lessons, linked Blooket sets, and review documents. Each front is a question; each back is the answer. Use Practice Test for automatic multiple-choice options.

What is evolution at the population level?

Change in allele frequencies across generations

What is required for natural selection to change a population?

Inherited variation that affects survival or reproduction

What does biological fitness mean?

Reproductive success in a given environment

Which event creates a new allele?

Mutation

What is artificial selection?

Humans choose which organisms reproduce for desired traits

What did Malthus's work help Darwin recognize?

Populations can produce more offspring than resources support

Which idea of Lamarck is generally rejected?

Acquired characteristics are routinely inherited

Which pair best illustrates homologous structures?

Human arm and whale flipper bones

What do analogous structures mainly show?

Similar function that evolved independently

What is a vestigial structure?

A reduced inherited feature with little or changed function

Which evidence is most useful for comparing distant evolutionary relationships?

DNA or protein sequences

What is biogeography?

Study of species' geographic distributions

In the Hardy-Weinberg model, what does p + q = 1 represent?

Frequencies of two alleles

In the Hardy-Weinberg model, what does 2pq represent?

Heterozygote frequency

If a recessive phenotype appears in 9% of a population at equilibrium, what is q?

0.30

If p = 0.7 and q = 0.3, what is the expected heterozygote frequency?

0.42

Which condition is required for Hardy-Weinberg equilibrium?

Random mating

Why is Hardy-Weinberg equilibrium useful?

It gives a null model for detecting evolutionary change

What is genetic drift?

Random change in allele frequencies, especially in small populations

What is a bottleneck effect?

A sharp population reduction that leaves a chance sample of alleles

What is a founder effect?

A few individuals start a new population with a limited allele sample

What is gene flow?

Movement of alleles between populations through migration and reproduction

Which selection pattern favors one extreme phenotype?

Directional

Which selection pattern favors intermediate phenotypes?

Stabilizing

Which selection pattern favors both extremes over the middle?

Disruptive

What is sexual selection?

Selection based on success in obtaining mates

What is exaptation?

An existing trait gains a new function

How does antibiotic resistance usually spread?

Resistant bacteria survive treatment and reproduce

What is the biological species concept?

Members can interbreed and produce fertile offspring

What is allopatric speciation?

Species form after geographic isolation reduces gene flow

What is sympatric speciation?

Species form in the same geographic area as reproductive isolation develops

Which is a prezygotic barrier?

Different breeding seasons

Which is a postzygotic barrier?

Hybrid offspring are sterile

What is adaptive radiation?

Rapid diversification from one ancestor into different niches

What is divergent evolution?

Related lineages accumulate different traits

What is convergent evolution?

Distant lineages independently evolve similar traits

What does a node on a cladogram represent?

A common ancestor or branching event

What is a clade?

An ancestor and all of its descendants

What does an outgroup help identify?

Which traits are ancestral relative to the ingroup

What is a derived character?

A trait that arose in a lineage after its ancestor

What usually matters most when comparing relatedness on a cladogram?

The most recent shared node

What is a molecular clock?

Using sequence differences and mutation rates to estimate divergence time

What is the RNA world hypothesis?

Early RNA could store information and catalyze reactions

What did Miller-Urey type experiments show?

Organic molecules can form under some simulated early-Earth conditions

What is LUCA?

The last universal common ancestor of living lineages

Why does a horse-donkey hybrid often have reduced fertility?

Its mismatched chromosomes disrupt meiosis

What selection pattern favors one end of a trait range?

Directional selection

What selection pattern favors the middle of a trait range?

Stabilizing selection

What selection pattern favors both trait extremes?

Disruptive selection

At what biological level do allele frequencies change through evolution?

A population

What is the direct target of natural selection?

Expressed phenotypes of individuals

Which process moves alleles when individuals migrate and reproduce in another population?

Gene flow

Why is random genetic drift stronger in small populations?

Chance changes a larger fraction of their alleles

If q equals 0.4 for a two-allele locus, what is p?

0.6

If q squared equals 0.16, what is the recessive allele frequency?

0.4

If 36 percent show a recessive disease phenotype at equilibrium, what is the expected heterozygote frequency?

0.48

Why do fossils tend to appear in sedimentary rock?

Sediment can bury remains before they decay

If 200 grams undergo five half-lives, how much remains?

6.25 grams

What is the oldest layer in an undisturbed sequence of sedimentary rock?

The deepest layer

What does a node on a phylogenetic tree represent?

A common ancestor and branching event

What is a postzygotic barrier in which a hybrid is sterile?

Reduced hybrid fertility

What is a postzygotic barrier in which a hybrid dies or develops poorly?

Reduced hybrid viability

What is a postzygotic barrier that appears in later hybrid generations?

Hybrid breakdown

What is a prezygotic barrier caused by different breeding seasons?

Temporal isolation

What is a prezygotic barrier caused by incompatible sperm and egg proteins?

Gametic isolation

What evolutionary pattern occurs when distantly related organisms independently develop similar traits?

Convergent evolution

What evolutionary pattern occurs when one lineage splits into increasingly different lineages?

Divergent evolution

What pattern describes two interacting species adapting in response to each other?

Coevolution

What is the likely result of a severe bottleneck for genetic diversity?

A reduction in genetic diversity

Why can a founder population have different allele frequencies from its source?

A small group carries a chance sample of alleles

Why is the dominant phenotype frequency not usually equal to p squared?

It includes both dominant homozygotes and heterozygotes

How do you find q from a recessive phenotype frequency under Hardy-Weinberg assumptions?

Take the square root of that frequency

How do you calculate the expected heterozygote frequency from p and q?

Multiply 2pq

What is an index fossil useful for?

Comparing the relative ages of rock layers

Which speciation mode occurs after geographic separation?

Allopatric speciation

Which speciation mode occurs within the same geographic area?

Sympatric speciation

What is a prezygotic barrier based on different courtship signals?

Behavioral isolation

Who used fossils to show that species can go extinct?

Georges Cuvier

Which geologist argued that slow processes accumulate over deep time?

James Hutton

Which geologist linked present-day geological processes to the distant past?

Charles Lyell

What was the name of Charles Lyell's influential geology book?

Principles of Geology

Who proposed inheritance of traits acquired through use and disuse?

Jean-Baptiste Lamarck

Why does a scar usually not pass to an organism's offspring?

It does not change the DNA of its gametes

Who argued that populations can grow faster than their food supply?

Thomas Malthus

Who independently developed natural selection alongside Darwin?

Alfred Russel Wallace

On what ship did Darwin travel during his major voyage?

HMS Beagle

What was Darwin's 1859 book called?

On the Origin of Species

What phrase did Darwin use for evolutionary change from common ancestors?

Descent with modification

Which meiotic process exchanges DNA between homologous chromosomes?

Crossing over

Which meiotic process randomly distributes parental homologs to gametes?

Independent assortment

Which cell type must carry a mutation for it to be inherited by offspring?

A gamete or its precursor

What matters most when comparing biological fitness?

The number of surviving offspring produced

Why does overproduction create competition?

More offspring are born than resources can support

What population condition reduces the effect of genetic drift in Hardy-Weinberg equilibrium?

Very large population size

What migration condition does Hardy-Weinberg equilibrium assume?

No gene flow

What mating condition does Hardy-Weinberg equilibrium assume?

Random mating

Which symbol represents the expected homozygous dominant frequency?

p squared

Which symbol represents the expected homozygous recessive frequency?

q squared

If q is 0.4, what proportion is expected to be homozygous recessive?

0.16

How can gene flow occur between lion prides?

A migrating lion breeds in a new pride