Unit 8

acquired trait	A trait that an organism gains during its lifetime. It is not coded for as part of the organism’s DNA, therefore cannot be passed on.
adaptation	A trait an organism has that increases its chance to survive and/or reproduce.
adaptive radiation	Speciation in which a common ancestor rapidly divergents into many different species. (E.g. Darwin’s finches).
allele frequency	The relative abundance of an allele in a population. Expressed as decimal, a percentage, or a fraction.
analogous structures	Features of different species that are similar in function but not in structure. Based on the environment, not common ancestry.
behavioral adaptation	Something an organism does in order to survive and/or reproduce (E.g. hibernation, mating dance).
behavioral isolation	When two species that could reproduce do not based on different behaviors. For example the Western Meadowlark and Eastern Meadowlark have different mating calls therefore do not attempt to mate.
biological resistance	An evolutionary process by which, through a series of mutations, an organism is no longer killed by a chemical designed to kill that species. Bacteria can become resistant to antibiotics, weeds can become resistant to herbicides, and insects can become resistant to pesticides.
cladogram	A diagram that shows relationships between species based on observable physical characteristics.
coevolution	When two species evolve in direct relation to each other. (E.g. A hummingbird and the flower it pollinates).
comparative anatomy	Examining/comparing the internal structure of organisms that share a recent common ancestor. A type of evidence of evolution.
comparative biochemistry	Examining/comparing the protein or DNA sequences of organisms that share a recent common ancestor. A type of evidence of evolution.
comparative embryology	Examining/comparing embryonic development of organisms that share a recent common ancestor. A type of evidence of evolution.
convergent evolution	When distantly related organisms appear similar due to the environment. (E.g. The wings of a bird and the wings of an insect)
directional selection
disruptive selection
divergent evolution	When species with a common ancestor become more different overtime.
evolution	Change in the allele frequency of a population over time.
fitness	The number of offspring that an organism produces.
fossil record	The history of life. A type of evidence of evolution.
gene flow	When individuals move back and forth between two different populations. This process reduces the difference between the populations.
gene pool	All of the alleles of a population.
genetic diversity	The total number of genetic characteristics in the genetic makeup of a species. Populations with a high genetic diversity are considered to be stable.
genetic drift	A random event that drastically decreases population size. Drift often reduces genetic diversity.
geographic isolation	When one population is split into two or more due to being physically separated. If isolated long enough, this may lead to the formation of two species.
homologous structures	Features on different organisms with the same structure but different functions. (E.g. The forearms of mammals all share the same bones.)
inherited trait	A trait that an organism is born with.
mutation	A random change in an organism’s DNA.
natural selection	A mechanism of evolution. Charles Darwin’s theory. Organisms that are better adapted to their environment are more likely to survive, reproduce and pass on those traits. This process causes species to change and diverge over time.
phylogenetic tree	A branching diagram that shows relationships between species based on common ancestry.
physiological adaptation	A chemical an organism makes/produces in order to survive. (E.g. venom, web of a spider)
reproductive isolation	When two populations, that were once one species, no longer reproduce. Over time this will lead to the formation of two separate species.
speciation	The evolution of a new species.
species	A group of organisms that can and do mate and produce fertile offspring.
stabilizing selection
structural adaptation	Something an organism has in order to survive (E.g. long neck of a giraffe, sharp teeth of a predator)
temporal isolation	When two groups mate at different times, therefore they do not interbreed.
variation	Multiple versions of a phenotype within a population.
vestigial structures	A structure that is present but no longer functions. It is evidence of divergent evolution. (E.g. the human appendix)