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structural, behavioral, and physiological traits that make an organism fit for its environment

amino acids

the organic molecules that serve as the units from which proteins are made


reaction that does not need oxygen

comparative embryology

the study of similarities and differences in the embryos of different organisms


type of prokaryote, blue-green, mostly photosynthetic


having 2 parts

directional selection

selection that tends to favor one extreme form of a trait over another

disruptive selection

a type of natural selection in which individuals with both extreme traits are favored and individuals with the average trait are not favored


groups of organisms made of one or more cells that have a membrane-bounded nucleus and membrane-bounded organelles


the change in allele frequencies in a population over time


the remains of ancient living things

gene pool

all the genes in all the members of a population

genetic drift

a change in the gene frequency of a population due to random events

genetic recombination

the movement of genes from one homologous chromosome to another via crossing-over during meiosis

genetic variation

genetic diversity in a population

homologous structures

structures that occur in different species but are similar enough to suggest that the species had a common ancestor


a regular movement of animals to a different location because of weather conditions, or of food, water, or shelter requirements


a change in a DNA molecule or in the structure of a chromosome

natural selection

the process in which the natural environment acts on individuals so that those with favorable traits survive and reproduce and those that do not have those traits are eliminated


Relating to or based on evolutionary development or history

phylogenetic tree

a diagram displaying the evolutionary relationships of types of organisms


the evolutionary history of organisms


all of the members of one species that live in a common area and whose population dynamics are different from those of other populations


organisms that usually are made of a single cell and do not have a membrane-bound nucleus or membrane-bound organelles

radiometric dating

a way of determining the absolute age in years of geologic samples using radioactive isotopes

stabilizing selection

selection that favors the average form of a trait over extreme forms


some of the oldest fossils, dome structures built by cyanobacteria


the science of naming and classifying organisms based on their natural relationships

vestigial structures

structures that appear to have no function for the organism but probably had a function in an ancestral organism

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