Bio 110

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fossils:

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Skeletons, bones, shells, body parts, leaves, seeds, or impressions of such items that provide recognizable evidence of organisms that lived long ago.

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geographic isolation:

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Separation of populations of a species for fairly long times into different areas

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background extinction:

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Normal extinction of various species as a result of changes in local environmental conditions. Compare mass extinction

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microevolution:

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The small genetic changes a population undergoes. Compare macroevolution.

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mass extinction:

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A catastrophic, widespread, often global event in which major groups of species are wiped out over a short time compared with normal (background) extinctions. Compare background extinction.

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generalist species:

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Species with a broad ecological niche. They can live in many different places, eat a variety of foods, and tolerate a wide range of environmental conditions. Examples are flies, cockroaches, mice, rats, and human beings. Compare specialist species

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fundamental niche:

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The full potential range of the physical, chemical, and biological factors a species can use if there is no competition from other species. See ecological niche. Compare realized niche.

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biological evolution:

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Change in the genetic makeup of a population of a species in successive generations. If continued long enough, it can lead to the formation of a new species. Note that populationsÑnot individualsÑevolve. See also adaptation, differential reproduction, natural selection, theory of evolution.

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mutation:

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A random change in DNA molecules making up genes that can yield changes in anatomy, physiology, or behavior in offspring. See mutagen

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realized niche:

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Parts of the fundamental niche of a species that are actually used by that species. See ecological niche, fundamental niche.

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specialist species:

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Species with a narrow ecological niche. They may be able to (1) live in only one type of habitat, (2) tolerate only a narrow range of climatic and other environmental conditions, or (3) use only one type or a few types of food. Compare generalist species.

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gene flow:

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Movement of genes between populations, which can lead to changes in the genetic composition of local populations.

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adaptive radiation:.

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Process in which numerous new species evolve to fill vacant and new ecological niches in changed environments, usually after a mass extinction. Typically, this takes millions of years.

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extinction:

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Complete disappearance of a species from the earth. This happens when a species cannot adapt and successfully reproduce under new environmental conditions or when it evolves into one or more new species. Compare speciation. See also endangered species, threatened species.

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adaptation:

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Any genetically controlled structural, physiological, or behavioral characteristic that helps an organism survive and reproduce under a given set of environmental conditions. It usually results from a beneficial mutation. See biological evolution, differential reproduction, mutation, natural selection

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differential reproduction:

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Phenomenon in which individuals with adaptive genetic traits produce more living offspring than do individuals without such traits. See natural selection.

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macroevolution:

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Long-term, large-scale evolutionary changes among groups of species. Compare microevolution.

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reproductive isolation:

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Long-term geographic separation of members of a particular sexually reproducing species

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ecological niche:

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Total way of life or role of a species in an ecosystem. It includes all physical, chemical, and biological conditions a species needs to live and reproduce in an ecosystem. See fundamental niche, realized niche.

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coevolution:

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Evolution in which two or more species interact and exert selective pressures on each other that can lead each species to undergo various adaptations. See evolution, natural selection

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gene pool:

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The sum total of all genes found in the individuals of the population of a particular species

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allele:

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Slightly different molecular form found in a particular gene

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speciation:

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Formation of two species from one species as a result of divergent natural selection in response to changes in environmental conditions; usually takes thousands of years. Compare extinction.

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genetic drift:

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Change in the genetic composition of a population by chance. It is especially important for small populations

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theory of evolution:

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Widely accepted scientific idea that all life-forms developed from earlier life-forms. Although this theory conflicts with the creation stories of many religions, it is the way biologists explain how life has changed over the past 3.6Ð3.8 billion years and why it is so diverse today.

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natural selection:

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Process by which a particular beneficial gene (or set of genes) is reproduced in succeeding generations more than other genes. The result of natural selection is a population that contains a greater proportion of organisms better adapted to certain environmental conditions. See adaptation, biological evolution, differential reproduction, mutation.