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What is evolution?

Change in the characteristics or allele frequencies of a population across generations.

Why do individuals NOT evolve?

Evolution occurs when the genetic makeup of a population changes across generations. Individuals can change during their lifetime, but populations evolve.

What is natural selection?

A process in which individuals with heritable traits that improve survival or reproduction tend to leave more offspring, causing those traits to become more common.

How does natural selection produce evolutionary change?

Individuals vary, some variation is heritable, individuals with advantageous traits reproduce more, and those traits become more common over generations.

What is required for natural selection to work?

Variation, heritability, and differential reproductive success.

What is an adaptation?

A heritable trait that increases an organism's ability to survive and/or reproduce in its environment.

What is the difference between Lamarckian evolution and Darwin/Wallace's view?

Lamarck proposed that organisms acquire traits through use and disuse and pass them to offspring; Darwin and Wallace proposed that natural selection acts on existing heritable variation.

What observations did Darwin and Wallace make?

Organisms vary, some variation is heritable, organisms produce more offspring than can survive, and individuals compete for limited resources.

How do mutations affect genetic diversity?

Mutations create new genetic variation, including new alleles.

How does sexual reproduction affect genetic diversity?

Sexual reproduction reshuffles existing alleles, producing genetically different offspring.

Mutation vs. sexual reproduction

Mutation creates new alleles; sexual reproduction rearranges existing alleles.

What is convergent evolution?

Unrelated organisms independently evolve similar traits because they experience similar selective pressures.

What is divergent evolution?

Related populations become increasingly different as they experience different environments or selective pressures.

What are five major lines of evidence for evolution?

Fossil record, anatomy, embryology, biogeography, and molecular biology.

What does the fossil record provide evidence for?

It provides evidence of organisms from different periods and shows changes in organisms through time.

What does comparative anatomy reveal?

Similarities and differences in anatomical structures can provide evidence of evolutionary relationships.

What does embryology provide evidence for?

Similarities in embryonic development can indicate evolutionary relationships.

What does biogeography study?

The geographic distribution of organisms and how it provides evidence for evolutionary history.

Why is molecular biology evidence for evolution?

Similarities in DNA, genes, and proteins can reveal common ancestry.

What is a species?

A group of organisms capable of reproducing with one another and producing viable, fertile offspring.

What is allopatric speciation?

Speciation caused by geographic separation of populations.

What is sympatric speciation?

Speciation occurring without geographic separation.

How can geographic isolation lead to new species?

A population becomes separated, gene flow is reduced or stopped, populations accumulate genetic differences, reproductive isolation develops, and they become separate species.

Why is gene flow important to speciation?

Gene flow mixes alleles between populations; reduced or absent gene flow allows populations to diverge genetically.

What is adaptive radiation?

Rapid diversification of one ancestral lineage into multiple species adapted to different ecological niches.

What is reproductive isolation?

Mechanisms that prevent populations from successfully reproducing with one another.

What is a prezygotic barrier?

A reproductive barrier that prevents fertilization from occurring.

What are four prezygotic barriers?

Temporal, habitat, behavioral, and mechanical isolation.

What is temporal isolation?

Populations reproduce at different times.

What is habitat isolation?

Populations live or reproduce in different habitats, so they rarely encounter one another.

What is behavioral isolation?

Differences in courtship or mating behaviors prevent reproduction.

What is mechanical isolation?

Anatomical differences prevent successful mating or transfer of gametes.

What is a postzygotic barrier?

A reproductive barrier that occurs after fertilization.

What are two postzygotic barriers?

An inviable zygote or hybrid, and infertile hybrid offspring.

Prezygotic vs. postzygotic barriers

Prezygotic barriers occur before fertilization; postzygotic barriers occur after fertilization.

What is a hybrid zone?

An area where previously separated populations or species come into contact and produce hybrids.

What are three possible outcomes when diverged populations reconnect?

Reinforcement, stabilization, or fusion.

What is reinforcement?

Natural selection strengthens reproductive isolation because hybrids have reduced fitness.

What is fusion?

Previously separated populations merge because reproductive barriers are weak enough for substantial gene flow.

What is stabilization?

Populations remain distinct despite coming into contact.

What is gradualism?

Evolutionary change occurs slowly and continuously over long periods.

What is punctuated equilibrium?

Long periods of relatively little evolutionary change interrupted by relatively rapid periods of change or speciation.

What is the difference between gradualism and punctuated equilibrium?

Gradualism involves slow, continuous change; punctuated equilibrium involves long periods of little change interrupted by relatively rapid evolutionary change.

What is a gene?

A segment of DNA associated with a particular biological function or trait.

What is an allele?

A particular version of a gene.

What is a genotype?

An individual's genetic makeup.

What is a phenotype?

The observable characteristics of an organism.

Genotype vs. phenotype

Genotype is genetic information; phenotype is the observable result of genetic information interacting with the environment.

What does diploid mean?

Having two sets of chromosomes.

What does haploid mean?

Having one set of chromosomes.

What is microevolution?

Evolutionary change occurring within a population, such as changes in allele frequencies.

What is macroevolution?

Evolutionary patterns or changes occurring at or above the species level.

What is allele frequency?

The proportion of a particular allele in a population.

What is genotype frequency?

The proportion of individuals with a particular genotype in a population.

What actually changes when a population evolves?

The frequencies of alleles or genotypes in the population change across generations.

What is the Hardy-Weinberg equation for allele frequencies?

p + q = 1

What does p represent in Hardy-Weinberg?

The frequency of one allele; the study guide labels it the dominant allele frequency.

What does q represent in Hardy-Weinberg?

The frequency of the other allele; the study guide labels it the recessive allele frequency.

What is the Hardy-Weinberg genotype-frequency equation?

p² + 2pq + q² = 1

What does p² represent?

Homozygous dominant genotype frequency.

What does 2pq represent?

Heterozygous genotype frequency.

What does q² represent?

Homozygous recessive genotype frequency.

What does Hardy-Weinberg equilibrium mean?

If the population meets the required assumptions, allele and genotype frequencies remain constant across generations.

What are the five Hardy-Weinberg assumptions?

Large population with no genetic drift, no mutation, random mating, no natural selection, and no gene flow.

Why does a small population violate Hardy-Weinberg equilibrium?

Small populations are more vulnerable to random changes in allele frequencies through genetic drift.

What can cause a population to violate Hardy-Weinberg equilibrium?

Mutation, genetic drift, nonrandom mating, natural selection, or gene flow.

What does adaptive evolution select for and against?

It selects for beneficial traits and against deleterious traits.

What is relative fitness?

An individual's reproductive success relative to other individuals in the population.

What is stabilizing selection?

Selection favors the intermediate phenotype and selects against extremes.

What is directional selection?

Selection favors one extreme phenotype, shifting the population toward that extreme.

What is diversifying selection?

Selection favors both extreme phenotypes over the intermediate phenotype.

What is sexual selection?

Selection resulting from differences in ability to obtain mates or reproductive opportunities.

How do stabilizing, directional, and diversifying selection differ?

Stabilizing favors the middle; directional favors one extreme; diversifying favors both extremes.

What is the handicap principle?

Costly traits can function as signals of an individual's underlying quality because individuals with greater fitness can afford the cost.

What is the good genes theory?

Mate preferences may favor traits that signal genetic quality.

What are the major taxonomic levels?

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

What is the binomial naming system?

A two-part scientific naming system using genus and species.

What does a rooted phylogenetic tree show?

Evolutionary relationships with a common ancestral root.

What is a branch point or node?

A point representing a common ancestor or evolutionary divergence.

What are sister taxa?

Two groups that share an immediate common ancestor.

What is a basal taxon or outgroup?

A lineage that branches off near the base of the tree and is used as a comparison for determining ancestral and derived traits.

What is an extinct taxon?

A group that no longer exists.

What is an extant taxon?

A group that is currently living.

Does the left-to-right order of branches on a phylogenetic tree determine relatedness?

No. Relatedness is determined by the branching pattern and common ancestry.

Can branches be rotated around a node without changing evolutionary relationships?

Yes.

How do you determine which organisms are most closely related on a phylogenetic tree?

Look for organisms that share the most recent common ancestor, not organisms that are simply drawn closest together.

What matters more than the visual order of branches?

The branching pattern and common ancestry.

What is a homologous structure?

A structure shared because of common ancestry, even if it has different functions.

What is an analogous structure?

A structure with similar function or form that evolved independently rather than from the same ancestral structure.

Homologous vs. analogous structures

Homologous means the same evolutionary origin; analogous means similar function or form evolved independently.

How can DNA homology reveal evolutionary relationships?

More similar DNA sequences generally indicate greater evolutionary relatedness or common ancestry.

What is a character trait in phylogenetic analysis?

A feature or characteristic used to compare organisms and determine evolutionary relationships.

What is a shared derived character or synapomorphy?

A derived trait shared by members of a particular clade and inherited from their common ancestor.

What is a shared ancestral character or plesiomorphy?

An ancestral trait shared by multiple groups.

What is a novel derived character or autapomorphy?

A derived trait unique to a particular lineage or group.

Why are shared derived traits useful for building phylogenies?

They can identify groups that share a more recent common ancestor.

What is a monophyletic group?

A group containing a common ancestor and all of its descendants.

What is a paraphyletic group?

A group containing a common ancestor but not all of its descendants.

What is a polyphyletic group?

A group whose members come from different evolutionary lineages and excludes their most recent common ancestor.

Monophyletic vs. paraphyletic vs. polyphyletic

Monophyletic contains the ancestor and all descendants; paraphyletic contains the ancestor and some descendants; polyphyletic groups organisms from separate lineages without their most recent common ancestor.