Ch 14: Origin of Life
biogenesis a principle which states that all living things come from other living things.
spontaneous generation the old ideal that life is generated spontaneously by their environments.
coacervate a collection of droplets that are composed as molecules of different types, like linked amino acids and sugars.
half-life the length of time it takes for one half of any size sample of an isotope to decay.
isotope an atom of the an element that contains a different number of neutrons than other atoms of the same element.
mass number in an isotope, the total number of protons and neutrons in the nucleus.
microsphere a structure that forms spontaneously in laboratories from solutions of simple organic chemicals (spherical in shape, composed of many protein molecules that comprise a membrane.
radioactive dating methods of establishing the age of materials in which the amount of a particular radioactive isotope is measures in the material and compared with its half-life.
radioactive decay the release of particles or radiant energy by an isotopes nucleus.
radioactive isotope an isotope that releases particles or radiant energy.
archaebacteria a kingdom of unicellular organisms that thrives under extremely harsh conditions.
chemosynthesis a process during which CO2 serves as a carbon source for the assembly of organic molecules (energy is obtained from the oxidation of various inorganic substances, like sulfer).
cyanobacteria a modern group of photosynthetic unicellular prokaryotes.
endosymbiosis a mutual, equally beneficial relationship between bacteria.
ozone O3 that is created by a reaction between single O atoms and O2 atoms (especially harmful to plant and animal life, but in the atmosphere ozone absorbs ultraviolet light from the sun).
ribozyme a term used by Thomas Cech to describe an RNA molecule that can act as an enzyme and promote a specific chemical reaction (hypothetically, a ribozyme could act as an enzyme and have the ability to replicate itself).
absolute age a fossils age in years (can be estimated by the amount of sediment deposited above the fossil).
biogeography the study of the geographical distribution of fossils and of living organisms.
cast a rocklike model of an organism formed by the filling of a mold with hard minerals.
extinct an adjective describing the death of an organism.
fossil a trace of a long-dead organism found in layers of sedimentary rock.
law of superposition states that successive layers of rock or soil were deposited atop each other with wind or water over time.
mass extinction brief periods during which large numbers of species disappear.
mold an imprint in a rock in the shape of an organism.
relative age a fossils age in comparison to the age of other fossils (deducible by Stenos law, comparing with older than or younger than).
sediment dust, sand, or mud that creates layers of sedimentary rock under which fossils are found.
stratum a layer of sedimentary rock.
acquired trait a trait that is not determined by genes but rather by an organisms experience throughout life.
adapt an organisms change as its proportion of genes for favorable traits increases.
fitness describes a single organisms genetic contribution to the next generation.
natural selection a process during which organisms best suited to their environment reproduce more successfully than other organisms.
population interbreeding single-species group of organisms.
uniformitarianism a principle that holds that the geological structure of Earth resulted from cycles of observable processes and that these same processes operate continuously throughout time.
adaptive radiation the evolution of many related species from a single ancestral species.
analogous features that serve identical functions and look very similar.
artificial selection the breeding of a species to purposefully attain a characteristic.
coevolution the change of two or more species in close association with each other.
conserve (when referring genes) to remain unchanged (like the hind leg genes of whales).
convergent evolution occurs when the environment selects similar phenotypes, even though the ancestral types were quite different from each other.
divergent evolution occurs when two or more related populations or species become more and more dissimilar.
homologous adjective used to describe features found in organisms and their ancestors.
vestigial apparently useless features.
allele frequency determined by dividing the number of a certain allele by the total number of alleles of all types in the population.
bell curve the statistical graph representation of lifespans (few animals live short lives, few live long lives, and most live lives of an average length).
gene pool describes total genetic information available in a given population.
Hardy-Weinberg genetic equilibrium shows that allele frequencies in a population tend to remain the same from generation to generation unless acted on by outside influences, assuming that: (1) no net mutations occur; that is, allele frequencies do not changes overall because of mutation; (2) individuals neither enter nor leave the population; (3) the population is large; (4) individuals mate randomly; (5) selection does not occur.
phenotype frequency the number of individuals with a particular phenotype divided by the number of individuals in a population.
population genetics the study of evolution from a genetic point of view.
assortative mating selection of a mate based on similarity of characteristics.
directional selection individuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the trait.
disruptive selection individuals with either extreme variation of a trait have greater fitness than individuals with the average form of the trait.
emigration the movement of individuals out of a population.
gene flow the process of genes moving from one population to another.
genetic drift phenomenon by which allele frequencies in a population change as a result of random events, or chance.
immigration the movement of individuals into a population.
sexual selection the choosing of mates based on certain traits.
stabilizing selection individuals with the average form of a trait have the highest fitness.
biological species concept proposed by Ernst Mayr, posits that a species is a population of organisms that can successfully interbreed but cannot breed with other groups.
geographic isolation the physical separation of members of a population.
morphology the internal and external structure and appearance of an organism.
postzygotic isolation reproductive isolation that occurs after fertilization.
prezygotic isolation reproductive isolation that occurs before fertilization.
punctuated equilibrium a pattern of species formation in which organisms change quickly rather than over long periods of time.
reproductive isolation results from barriers to successful breeding between population groups in the same area.
speciation the process of species formation that results in many related populations of organisms.