Biology 112 - Exam 1 Concepts

What is natural selection?

Differential survival and reproduction of individuals with heritable traits that increase fitness.

Does natural selection create new traits?

No. It sorts existing variation; mutations create new variation.

What is required for natural selection?

Variation, heritability, differential reproductive success.

Example of natural selection from the exam?

Birds eating lighter beetles → darker beetles survive more.

What is stabilizing selection?

Selection that favors intermediate phenotypes and reduces variation.

What is directional selection?

Selection that shifts the average phenotype in one direction.

What is disruptive selection?

Selection that favors extreme phenotypes and increases variation.

What is convergent evolution?

Unrelated species evolve similar traits due to similar environments.

What is divergent evolution?

Related species evolve different traits due to different environments.

What is adaptive radiation?

Rapid diversification from one ancestor into many species occupying different niches.

What conditions trigger adaptive radiation?

Many empty ecological niches OR key innovations.

What is allopatric speciation?

Speciation due to geographic isolation.

What is sympatric speciation?

Speciation without geographic separation.

What is temporal isolation?

Species breed at different times.

What is behavioral isolation?

Differences in mating behaviors prevent reproduction.

What is mechanical isolation?

Reproductive structures are incompatible.

What is hybrid sterility?

Offspring survive but cannot reproduce.

What does p represent?

Frequency of the dominant allele.

What does q represent?

Frequency of the recessive allele.

If q² = 0.16, what is q?

0.4

What is the heterozygote frequency formula?

2pq

What violates Hardy–Weinberg equilibrium most strongly?

Strong natural selection.

What is genetic drift?

Random change in allele frequencies.

What is the bottleneck affect?

Sudden reduction in population size causing random allele loss.

What is a founder effect?

A new, isolated population is established by a very small number of individuals from a larger parent population

What is gene flow?

Movement of alleles between populations.

What does gene flow do to populations?

Reduces genetic differences between them.

What is evolution?

Change in allele frequencies over generations.

Does evolution occur in individuals?

No — only populations evolve.

What is a node?

A common ancestor where lineages split.

What is a tip?

A living or extinct species.

What are sister taxa?

Two species that share a recent common ancestor.

What is a monophyletic group?

An ancestor and all its descendants.

What is the least related species on a tree?

The one branching off farthest from the target species.

What was the Cambrian Explosion?

Rapid diversification of animal body plans ~541 mya.

What contributed to the Cambrian Explosion?

Increased oxygen levels.

Relationship between micro- and macroevolution?

Macroevolution is the accumulation of microevolutionary changes.