DC Biology 1407 Unit 1 Exam (Evolution & Phylogeny)

natural selection

A process in which individuals with certain inherited traits tend to survive and reproduce at higher rates than others.

effect of natural selection

Changes in phenotypic allele frequency in a population.

gene flow

Movement of alleles from one population to another population that does not migrate.

mutation

Change in a DNA sequence that affects genetic information, the ultimate source of genetic variation.

genetic drift

Random change in allele frequencies that occurs in small populations.

fitness

The reproductive success of an individual relative to the average reproductive success of the population.

bottleneck effect

A reduction in the genetic diversity of a population caused by a reduction in its size.

founder effect

Change in allele frequencies as a result of the migration of a small subgroup of a population.

vestigial structures

A structure that is present in an organism but no longer serves its original purpose.

homologous structures

Similar structures that related species have inherited from a common ancestor.

analogous structures

Similarities among unrelated species that result from convergent evolution.

Hardy-Weinberg equilibrium

Condition that occurs when the frequency of alleles in a gene pool remain constant over time.

Hardy-Weinberg equation

p2 + 2pq + q2 = 1.

directional selection

Occurs when natural selection favors one of the extreme variations of a trait.

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes.

disruptive selection

Natural selection in which a single curve splits into two; extremes have higher fitness than individuals near the middle.

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments.

divergent evolution

When two or more species sharing a common ancestor become more different over time.

artificial selection

Breeding organisms with specific traits to produce offspring with identical traits.

Archaeopteryx

An intermediate fossil that shows both dinosaur and bird characteristics.

biogeography

The study of geographic distribution of species and ecosystems.

molecular clock

Model that uses DNA comparisons to estimate the length of time that two species have been evolving independently.

evidence of evolution

Includes fossil record, embryology, homologous structures, DNA, and vestigial structures.

gradualism

The theory that evolution occurs slowly but steadily.

punctuated equilibrium

Pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change.

allopatric speciation

The formation of new species in populations that are geographically isolated.

sympatric speciation

The formation of new species in populations that live in the same geographic area.

prezygotic isolation

A barrier to successful breeding that occurs before fertilization.

ecological isolation

Species occur in the same area but occupy different habitats.

behavioral isolation

Differences in courtship rituals that prevent two populations from interbreeding.

temporal isolation

Reproductive isolation in which two populations reproduce at different times.

mechanical isolation

Morphological (physical) differences can prevent successful mating.

prevention of gamete fusion

Gametes of one species function poorly with the gametes of another species.

postzygotic isolation

Reproductive isolation occurring after hybrid offspring are produced.

hybrid sterility

Postzygotic barrier where the hybrid is infertile.

Biological Species Concept (BSC)

Defines species as groups of interbreeding populations that are reproductively isolated.

phylogenetic species concept

Defines species as the smallest group of individuals that share a common ancestor.

autopolyploidy

Chromosome duplication in a single species to form tetraploid.

allopolyploidy

Polyploidy resulting from contribution of chromosomes from two different species.

systematics

Study of the diversity of life and the evolutionary relationships between organisms.

phylogeny

Evolutionary history of a species or group of species.

derived characters

Characteristics that appear in recent parts of a lineage, but not in older members.

clade

A group of species that includes an ancestral species and all its descendants.

synapomorphies

Shared derived characters by a clade.

plesiomorphies

Ancestral character states.

symplesiomorphies

Shared ancestral states.

polyphyletic group

A taxonomic grouping consisting of several species that lack a common ancestor.

monophyletic group

Group that consists of a single ancestral species and all its descendants.

homoplasy (convergent evolution)

Independent evolution of similar features in species of different lineages.

endosymbiosis

Process in which early eukaryotic cells were formed from simpler prokaryotes.

principle of parsimony

When competing explanations fit the facts, the simplest is preferred.