| A | B |
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| Evolution | The process by which modern organisms have descended from ancient organisms. |
| Theory | A well-supported testable explanation of phenomena that have occured in the natural world. |
| Fossil | Preserved remains of ancient organisms. |
| Artificial Selection | Selection by humans for breeding of useful traits from the natural variation among different organisms. |
| Struggle for Existence | Members of each species compete regularly to obtain food, living space, and other necessities of life. |
| Fitness | The ability of of an individual to survive and reproduce in its specific environment. |
| Adaption | Inherited characteristic that increases an organism's chance of survival. |
| Survival of the Fittest | Individuals that are better suited to their environment survive and reproduce successfully. |
| Natural Selection | ndividuals that are better suited to their environment survive and reproduce successfully. Also known as survival of the fittest. |
| Descent with Modification | Each living species had descended, with changes, from other species over time. |
| Common Descent | All species are derived from common ancestors. |
| Homologous Structure | Structures that have different mature forms but develop from the same clump of cells in embryos. |
| Vestigal Organ | Vestiges, or traces, of homologous organs in other species. |
| Gene Pool | A common group of genes that consists of all genes, including all the different alleles, that are present in a population. |
| Relative Frequency | The number of times that an allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur. |
| Single-gene Trait | A trait that is controlled by a single gene that has two alleles. |
| Polygenic Trait | Many traits that are controlled by two or more genes. |
| Directional Selection | When individuals at one end of the curve have higher fitness than individuals in the middle or at the other end. |
| Stabilizing Selection | When individuals near the cneter of the curve have higher fitness than individuals at either end of the curve. |
| Disruptive Selection | When individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle. |
| Genetic Drift | Random changes in allele frequency that occurs in small populations. |
| Founder Effect | A situation in which allele frequencies change as a result of the migration of a small subgroup of a population. |
| Hardy-Weinberg Principle | A principle that states that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change. |
| Genetic Equilibrium | The situation in which allele frequencies remain constant. |
| Speciation | The formation of new species. |
| Reproductive Isolation | When the members of two populations cannot interbreed and produce fertile offspring. |
| Behavioral Isolation | A type pf isolating mechanism that occurs when members of two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior. |
| Geographic Isolation | Two populations are separated by geographic barriers such as rivers, mountains, or bodies of water. |
| Temporal Isolation | Two or more species reproduce at a different times. |
| Paleontologist | Scientists who study fossils. |
| Fossil Record | Information that provides evidence about the history of life on Earth. It also shows how different groups of organisms, including species, have changed over time. |
| Extinct | The dying out of a species. |
| Relative Dating | Determining the age of a fossil by comparing its placement with that of fossils in other layers of rock. |
| Index Fossil | Fossils used to compare the relative age of fossils. |
| Half-Life | The length of time required for half of the radioactive atoms in a sample to decay. |
| Radioactive Dating | The use of half-lives to determine the age of a sample. |
| Geologic Time Scale | Scales used by paleontologists to represent evolutionary time. |
| Era | One of several subdivisions of the time between the Precambrian and the present. |
| Period | A unit of time that eras are subdivided into. |
| Proteinoid Microsphere | The tiny bubbles formed by large organic molecules under certain conditions. |
| Microfossil | Microscopic fossils. |
| Endosymbiotic Theory | Eukaryoticcells formed from a symbiosis among several different prokaryotic organisms. |
| Mass Extinction | Many types of living things become extinct at the same time. |
| Macroevolution | Large-scale evolutionary patterns and processes that occur over long periods of time. |
| Adaptive Radiation | The evolution of a single species or a small group of species through natural selection and other processes, into diverse forms that live in different ways. |
| Convergent Evolution | The process by which unrelated organisms come to resemble one another. |
| Coevolution | The process by which two species evolve in repsone to changes in each other over time. |
| Punctuated Equilibrium | Used to describe a pattern of long, stable periods interrupted by brief periods of more rapid change. |
| Taxonomy | The classifying of organisms and the assigning each organism a universally accepted name. |
| Binomial Nomenclature | A two word naming system for organisms. |
| Genus | A group of closely related species. |
| Taxon | A level in taxonomic nomenclature. |
| Family | A large category of genera that share many characteristics. |
| Order | A broad taxonomic category composed of similar families. |
| Class | A large category consisting of similar orders. |
| Phylum | A group make up of several different classes. |
| Kingdom | The largest and most inclusive of Linnaeus's taxonomic categories. |
| Phylogeny | The study of evolutionary relationships among organisms. |
| Evolutionary Classification | The strategy of grouping organisms together based on their evolutionary history. |
| Derived Character | Characteristics that appear in recent parts of a lineage but not in its older members. |
| Cladogram | A diagram that shows the evolutionary relationships among a group of organisms. |
| Molecular Clock | A model that uses DNA comparisons to estimate the length of time that two species have been evolving independently. |
| Domain | A more inclusive category that is larger than a kingdom. |
| Bacteria | Domain of unicellular prokaryotes that have cell walls containing peptidoglycan. |
| Eubacteria | Kingdom of unicellular prokaryotes whose cell walls are made up of peptidoglycan. |
| Archaea | Domain of unicellular prokaryotes that have cell walls that do not contain peptidoglycan. |
| Archaebacteria | Kingdom of unicellular prokaryotes whose cell walls do not contain peptidoglycan. |
| Eukarya | DOmain ofall organisms whose cells have nuclei, including protists, plants, fungi, and animals. |
| Protista | Kingdom composed of eukaryotes that are not classified as plants, animals, or fungi. |
| Fungi | Kingdom composed of heterotrophs; many obtain energy and nutrients from dead organic matter. |
| Plantae | Kingdom of multicellular photosynthetic autotrophs that have cell walls containing cellulose. |
| Animalia | Kingdom of multicellular eukaryotic heterotrophs whose cells do not have cell walls. |
