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AP Bio Evolution

Chapter 22/23/24

TermDefinition
uniformitarianism The idea that the same geologic processes shaping the Earth today have been at work throughout Earth's history.
natural selection Mechanism by which individuals that have inherited beneficial adaptations produced more offspring on average than do other individuals
adaptations Certain variation that allows an individual to survive and reproduce better than individuals it competes against
artificial selection the intentional breeding of certain characteristics over others
homologous structures any structures that are similar due to shared ancestry
embryonic homologies comparison of early stages of animal development reveals many anatomical homologies in embryos that are not visible in adult organisms
vestigial organs anatomical structures of organisms in a species which have lost much or all of their original function due to evolution
molecular homologies shared characteristics on the molecular level.
convergent evolution where unrelated organisms evolve similar traits as a result of having to adapt to similar environments
endemic species native to or confined to a certain region; the species is found no where else in the world
microevolution is change in the allele frequencies of a population over generations. This is evolution on its smallest scale
mutations the only source of new genes and new alleles; only mutations in cell lines that produce gametes can be passed to offspring.
point mutations changes in one base in a gene. They can have significant impact on phenotype, as in sickle-cell disease
chromosomal mutations delete, disrupt, duplicate, or rearrange many loci at once. They are usually harmful
gene pool all of the alleles at all loci in all the mem ers of a population. In diploid species, each individual has 2 alleles for a particular gene, and the individual may be either heterozygous or homozygous.
population a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.
hardy-weinberg principle It states that the frequencies of alleles and genes in a population's gene pool will remain constant over the course of generations unless they are acted upon by forces other the Mendelian segregation and the recombination of alleles.
genetic drift is the unpredictable fluctuation in allele frequencies from one generation to the next. The smaller the population, the greater the chance is for genetic drift. This is a random, nonadaptive change in allele frequencies.
founder effect a few individuals become isolated from a larger population and establish a new population whose gene pool is not reflective of the source population.
bottleneck effect a sudden change in the environment (e.g. an earthquake, flood, or fire) that drastically reduces the size of a population. The few survivors that pass through the bottleneck may have a gene pool that no longer reflects that original population's gene pool
gene flow when a population gains or loses alleles by genetic additions to and/or subtractions from the population. Results from the movement of fertile individuals/gametes. reduces the genetic differences between populations,making populations more similar.
relative fitness refers to the contribution an organism makes to the gene pool of the next generation relative to the contributions of other members. Fitness does not indicate strength or size. It is measured only by reproductive success
directional selection occurs when conditions favor individuals exhibiting one extreme of a phenotypic range, thereby shifting a population's frequency curve for the phenotypic character in one direction or the other.
disruptive selection occurs when conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes
stabilizing selection Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes.
speciation An evolutionary process in which one species splits into two or more species.
reproductive isolation The existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring.
habitat isolation two species that occupy different habitats within the same area may encounter each other rarely, if at all, even though they are not isolated by obvious physical barriers such as mountain ranges. An example of prezygotic barriers.
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. An example of prezygotic barriers
temporal isolation species may breed at different times of day, different seasons, or different years, and this can prevent them from mating. An example of prezygotic barriers.
mechanical isolation species may be anatomically incompatible. An example of prezygotic barriers.
gametic isolation even if the gametes of 2 species do meet, they might be unable to fuse to form a zygote. An example of prezygotic barriers
reduced hybrid viability when a zygote is formed, genetic incompatibility may cause development to cease. An example of postzygotic barriers
reduced hybrid fertility even if the 2 species produce a viable offspring, reproductive isolation is still occurring if the offspring is sterile and can't reproduce. An example of postzygotic barriers.
hybrid breakdown sometimes 2 species mate and produce viable, fertile hybrids; however when the hybrids mate, their offspring are weak or sterile. An example of postzygotic barriers
allopatric speciation a population forms a new species because it is geographically isolated from the parent population
sympatric speciation a small part of a population becomes a new population without being geographically separated from the parent population. It can result from part of the population switching to a new habitat, food source, or other resource.
adaptive radiation are periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological niches.
gradualism proposes that species descended from a common ancestor and gradually diverge more and more in morphology as they acquire unique adaptations.
punctuated equilibrium a term used to describe periods of apparent stasis punctuated by sudden change observed in the fossil record.
oparine and haldane 1920s, hypothesized that under the conditions of early earth, organic molecules could form
Miller and Urey tested Oparin-Haldane hypothesis, proved that almost any energy source could have converted the molecules into a variety of organic materials, including amino acids
relative dating method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock
radiometric dating the process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products
endosymbiotic hypothesis a theory that proposes that mitochondria and plastids were formerly small prokaryotes living inside other host cells
hox genes one class of homeotic genes. Changes in Hox genes and in the genes that regulate them can have a profound effect on morphology, thus contributing to the potential for evolutionary change.
Created by: perkinscheyann