Evolution Flashcards
Microevolution
Changes in one gene pool of a population over generations.
Macroevolution
Refers to speciations, the formation of an entirely new species.
Population
Group of individuals of one species living in one area that have the ability of interbreeding and interacting with each other.
Transitional fossils
Fossils that link older extinct fossil to modern species. (have two features in one showing similarity)
Hyracotherium
the ancient horse-ancestor of modern horse. Example of transition fossil.
Homologous Structures
The same internal bone structure, although the function of each varies.
ex. the wing of a bat, the lateral fin of whale, and the human arm. If organisms have homologous structures, they have a common ancestor.
Analogous Structures
Structures, such as a bath’s wing and a fly’s wing, that have the same function but no the same underlying structure. The similarity is merely superficial and reflects adaptation to a similar environment. Analogous structures are not evidence of a common origin or common ancestry.
Vestigial Structures
Structures that are remnants of an earlier active structure, such as the appendix. They are evidence that animals have evolved.
Stabilizing Selection
This type of natural selection eliminates the extremes and favors the more common intermediate forms.
Disruptive Selection
This type of natural selection increases the numbers of extreme types in a population at the expense of intermediate forms.
Directional Selection
Changing environmental conditions give rise to this type of natural selection. One phenotype replaces another in the gene pool.
Genetic Drift
Change in the gene pool due to chance. Two examples are the bottleneck effect and the founder effect.
Bottleneck Effect
Natural disasters such as fire, earthquake, and flood reduce the size of a population nonselectively, resulting in a loss of genetic variation. The resulting population is much smaller and not representative of the original one.
Founder Effect
A small population, which is not representative of the larger population, breaks away from the larger one to colonize a new area. Rare alleles may be under- or overrepresented.
Gene Flow
Movement of alleles into or out of a population.
Polyploidy
An organism with extra sets of chromosomes. Commonly occurs in plants.
Habitat Isolation
Occurs when two organisms live in the same area but encounter each other rarely. Two species of one genus of snake can be found in the same geographic area, but one inhabits the water while the other is mainly terrestrial.
Behaivor Isolation
Occurs when two animals become isolated from each other because of some change in behavior by one member or group.
ex. FireFly blinking..
Divergent Evolution
Occurs when a population becomes isolated (for any reason) from the rest of the species and becomes exposed to new selective pressures, causing it to evolve into a new species. Homologous structures are evidence of divergent evolution.
Convergent Evolution
When unrelated species occupy the same environment, they are subjected to similar selective pressures and show similar adaptations.
ex. Whale body vs. Fish body. Serves same function, but are different.
Parallel Evolution
Describes two related species that have made similar evolutionary adaptations after their divergence from a common ancestor.
Coevolution
The mutual evolutionary set of adaptations of two interacting species.
Adaptive Radiation
The emergence of numerous species from a single common ancestor introduced into an environment.
ex. Darwin’s Finches
Punctuated Equilibrium
Theory that proposes that new species appear suddenly after long periods of stasis. Replaced gradualism theory in popularity.
