3.9: Key Terms

Adaptive radiation – an evolutionary process where a single ancestral species rapidly diversifies into multiple new species. This occurs when organisms encounter new environmental niches, such as after colonizing an isolated island chain or surviving a mass extinction, allowing them to evolve specialized traits to exploit different resources.

Artificial selection – The identification by humans of desirable traits in plants and animals, and the subsequent steps taken to enhance and perpetuate those traits in future generations.

Binomial nomenclature – A system of classification in which a species of animal or plant receives a name consisting of two terms: the first identifies the genus to which it belongs, and the second identifies the species.

Carrying capacity – The number of living organisms, including animals, crops, and humans, that a geographic area can support without environmental degradation.

Catastrophism – The theory that the Earth’s geology has largely been shaped by sudden, short-lived, violent events, possibly worldwide in scope. Compare to uniformitarianism.

Convergent evolution – the independent evolution of similar features in unrelated or distantly related species.

Differential reproductive success – the difference in the number of surviving offspring produced by individuals within a population. Those individuals with traits best suited to their environment are more likely to survive and pass those traits (and the genes that produce them) to the next generation

Fitness – an organism's ability to survive and reproduce in a specific environment, thereby passing its genes on to the next generation. It is not a measure of physical strength or speed, but rather a gauge of reproductive success and genetic contribution.

Heredity – the process by which traits and characteristics are transmitted from parents to their offspring.

Hierarchy – an organizational structure that ranks items, people, or concepts based on relative importance, authority, or status.

Holobiont – an ecological and evolutionary unit composed of a host organism (such as an animal or plant) and all its associated microorganisms, like bacteria, viruses, and fungi.

Inheritance of acquired characteristics – theory about evolutionary change proposed by French naturalist, Jean Baptiste-Lamarck, and later disproven, that the physical traits an organism develops during its lifetime to adapt to its environment can be passed on to its offspring.

Microbiome – a dynamic, highly complex community of microorganisms—including bacteria, viruses, fungi, and parasites—that live in a particular environment.

Scala Naturae – The Scala Naturae (Latin for "ladder of nature"), also known as the Great Chain of Being, is an ancient philosophical and religious concept. It arranges all matter, life, and celestial beings into a single, hierarchical, and continuous linear ladder based on complexity.

Social Darwinism – a late 19th-century pseudoscientific theory that applies the biological concepts of natural selection and "survival of the fittest" to human societies.

Uniformitarianism – The theory that changes in the earth’s crust during geologic history have resulted from the action of continuous and uniform processes—such as wind, precipitation, evaporation, condensation, erosion, and volcanic action—that continue to act in the present.

Variation – the differences between individuals within a species.

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