DC Biology 1407 Unit 1 Exam (Evolution & Phylogeny)
natural selection
A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
Affect 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, ultimate source of genetic variation
genetic drift
random change in allele frequencies that occurs in small populations
Fitness
The reproductive success (number of descendants) of an individual organism 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 particular 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
form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve 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 in order to produce offspring with identical traits. Changes can occur rapidly
Archaeopteryx
An intermediate fossil that shows both dinosaur and bird characteristics (feathers)
Biogeography
inhabitants of oceanic islands resemble forms from nearest mainland but some differences due to habitat
molecular clock
Model that uses DNA comparisons to estimate the length of time that two species have been evolving independently
Evidence of Evolution
1) Fossil Record
2) Embryology
3) Homologous Structures
4) DNA
5) 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 from one another.
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, such as differences in mating time or behavior
ecological isolation
species occur in the same area, but they occupy different habitats and rarely encounter each other
behavioral isolation
Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding
temporal isolation
form of 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 or within the reproductive tract of another species
postzygotic isolation
reproductive isolation that occurs after members of two different species have mated and produced a hybrid offspring. Such hybrids are usually unable to reproduce
hybrid sterility
postzygotic barrier; the hybrid is infertile or do not survive to adult
Biological Species Concept (BSC)
Defines species as groups of interbreeding populations that are reproductively isolated
phylogenetic species concept
A definition of species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.
Autopolyploidy
chromosome duplication in a single species to form tetraploid, can self-fertilize or mate with other tetraploids
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 (tree) of a species or group of species.
derived characters
Characteristic that appears in recent parts of a lineage, but not in its older members, seen in cladograms between branch points
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 (more work is needed to uncover species that tie them together into a monophyletic clade).
monophyletic group
group that consists of a single ancestral species and all its descendants and excludes any organisms that are not descended from that common ancestor
Homoplasy (convergent evolution)
independent evolution of similar features in species of different lineages
Endosymbiosis
A theorized process in which early eukaryotic cells were formed from simpler prokaryotes. Origin of chloroplasts and mitochondria
principle of parsimony
when competing explanations or theories fit the facts, the simplest is preferred. Create tree based on fewest character states