Evolutionary Biology Review

What is biological evolution?

A change in the genetic composition of a population from one generation to the next.

Do populations or individuals evolve?

Populations evolve.

What are the four evolutionary processes?

Mutation, migration/gene flow, genetic drift, and natural selection.

What is mutation?

The ultimate source of biological variation, permanent changes to DNA caused by replication or meiotic errors.

What is migration/gene flow?

The movement of genomes between populations, with introgression and admixture; this can occur between populations of different species via hybridization.

What is introgression?

The transfer of genetic material from one species/population into the gene pool of another through hybridization and repeated backcrossing.

What is admixture?

The mixing of genetic material from two populations.

What is genetic drift?

Random/stochastic transmission of alleles across generations, it acts independently of phenotype and is especially strong in small populations.

What is natural selection?

The non-random transmission of alleles due to associations between phenotype and reproductive success; phenotypes differ in fitness which causes associated alleles to increase in frequency.

What is microevolution?

Evolutionary change within populations.

When does speciation occur?

When divergence leads to reproductive isolation.

What is macroevolution?

Large-scale evolutionary patterns.

When does natural selection not occur?

If there is no heritable variation and/or traits are not associated with reproductive success.

What is fitness?

The number of copies of an individual’s genes passed to the next generation.

What is direct fitness?

Genes passed via own offspring.

What is indirect fitness?

Genes passed via relatives’ offspring.

What is inclusive fitness?

Direct + indirect fitness.

What are the components of fitness?

Survival (viability selection), reproductive output (fecundity selection), and mating success (sexual selection).

What is adaptation?

The close fit between phenotype and environment.

What does selection act on?

It acts on phenotypes, not directly on genes.

What does natural selection favor?

Traits that benefit individuals, not groups.

When do cooperative behaviors evolve?

If they increase direct or inclusive fitness.

What produces phenotype?

Genotype + environment

What produces fitness?

Phenotype + environment

What is evolution demonstrated by?

Genetic change in populations over time.

Why can evolution not be detected by looking at phenotypic change?

Phenotypes can change plastically due to the environment and genetic change can be neutral (genetic drift).

How can you identify mutation and gene flow?

Via genetic variation and population structure.

How can you infer genetic drift?

Bottlenecks, founder effects, and population genetic signals.

How can you detect natural selection?

Show genetic change, identify phenotypes associated with higher fitness, and use correlations between trait variation and reproductive success.

What is parallel evolution?

Repeated evolution of similar traits under similar selective pressures.

What is sexual selection?

Form of natural selection arising from variation in mating success.

What does sexual selection explain?

Traits that increase access to mates even if they reduce survival.

What are characteristics of male-male competition?

Direct aggression and contests, control of harems, scramble competition, and endurance rivalry.

What is sperm competition?

Occurs when females mate with multiple mates; it selects for large ejaculates, fast/long-lived sperm, prolonged copulation, mate guarding, and sperm displacement mechanisms.

What is mate choice?

Non-random mating success based on phenotypes of choosers & chosen individuals, not necessarily a conscious choice.

What are direct benefits of mate choice?

Resources, parental care, and protection.

What are indirect benefits of mate choice?

Attractive or high-quality offspring.

What is cryptic female choice?

Post-copulatory processes that bias fertilization toward certain males.

Why do sex roles differ?

• Anisogamy: eggs are more costly than sperm

• Producing eggs limits reproductive rate

• Females are often the limiting sex, while males are the competing sex

• Both sexes can be choosy & competitive

• Selection operates pre- and post-copulation

What is the ultimate source of biodiversity?

Mutation.

What do adaptations arise from?

Interactions between genes & ecological conditions.

What is the biological species concept?

Species are groups that interbreed naturally to produce fertile offspring, species cohesion is maintained by gene flow, and speciation occurs where gene flow is reduced/eliminated.

What are limitations of the BSC?

Hybridization and introgression across species boundaries, allopatric populations that never meet, cryptic species, and species flocks.

What is the morphological species concept?

It is based on physical form, but is subjective and prone to lumping/splitting.

What is the ecological species concept?

Species are defined by ecological niche.

What is the phylogenetic/molecular species concept?

It is based on genetic similarity (subjective thresholds).

What is pre-mating isolation?

Individuals fail to attract or stimulate heterospecific mates.

What is post-mating, pre-zygotic isolation?

Mating occurs but fertilization fails, includes mechanical failure and gamete incompatibility.

What is post-zygotic isolation?

Zygotes form but offspring is inviable/infertile, caused by genetic incompatibilities & negative epistatic interactions.

What is Haldane’s Rule?

If only one hybrid sex is infertile/inviable, it’s the heterogametic sex.

What is allopatric speciation?

Divergence in complete geographic isolation.

What is parapatric speciation?

Divergence with partial geographic overlap.

What is sympatric speciation?

Divergence within the same geographic area.

What does sympatric speciation require for it to occur?

Ecological isolation, often reinforced by sexual selection, and can often involve large genetic events like polyploidization.

What is an incipient species?

Populations in early stages of divergence where gene flow may still prevent full speciation.