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structural, behavioral, and physiological traits that make an organism fit for its environment
the study of similarities and differences in the embryos of different organisms
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 movement of genes from one homologous chromosome to another via crossing-over during meiosis
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
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
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
a way of determining the absolute age in years of geologic samples using radioactive isotopes
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