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chemical evolution

evolution of organic molecules, biopolymers, and systems of chemical reactions needed to form the first cells (took place around 1 billion years ago).

biological evolution

from single cell prokaryotic bacteria to single-celled eukaryotic creatures and then to multicellular organisms.


mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items.

evolution (biological evolution)

change in a population's genetic makeup through successive generations.

theory of evolution

all species descended from earlier, ancestral species (life comes from life).


describes the small genetic changes that occur in a population's gene pool over time.


describes the long term, large-scale evolutionary changes through which new species form from ancestral species and other species are lost through extinction.

gene pool

collection of genes or genetic resources potentially available to members' offspring in the next generation.


slightly different molecular form found in a particular gene.



natural selection

occurs when some individuals of a population have genetically based traits that increase their chances of survival and their ability to produce offspring with the same traits.

differential reproduction

the trait must enable individuals with the trait to leave more offspring than other members of the population.

adaptation (adaptive trait)

is any heritable trait that enables organisms to better survive and reproduce under prevailing environmental conditions.


when populations of two different species interact over a long time, changes in the gene pool of one species can lead to changes in the gene pool of the other.

ecological niche

it is a species' way of life or functional role in a community or ecosystem and involves everything that affects its survival and reproduction.


the physical location where it lives.

fundamental niche

is the full potential range of physical, chemical, and biological conditions and resources it could theoretically use if there were no direct competition from other species.

realized niche

a species usually occupies only part of its fundamental niche in a particular community or ecosystem.

generalist species

have broad niches; they can live in many different places, eat a variety of foods, and tolerate a wide range of environmental conditions.


two species arise from one.

geographic isolation

occurs when different groups of the same population become physically isolated from one another for long periods.

reproductive isolation

occurs when mutation and natural selection operate independently in the gene pools of two geographically isolated populations.

sympatric speciation

creation of a new species when groups in a population living close together are unable to interbreed because of a mutation or subtle behavioral changes.


which an entire species ceases to exist.

background extinction

certain number of species disappear at a low rate.

mass extinction

significant rise in extinction rates above the background level. It is a catastrophic, widespread event in which large groups of existing species are wiped out.

mass depletion

extinction rates are higher than normal but not high enough to classify as a mass extinction.

adaptive radiation

numerous new species evolved to fill new or vacated ecological roles or niches in changed environments.


the planet's genetic raw material for future evolution in response to changing environmental conditions.

artificial selection

in this process, we select one or more desirable genetic traits in the population of a plant or animal.

selective breeding

end up with populations of the species containing large numbers of individuals with the desired traits.

genetic engineering (gene splicing)

is a set of techniques for isolating, modifying, multiplying, and recombining genes from different organisms.

genetically modified organisms

resulting organisms from genetic engineering.

specialist species

these species have narrow niches. They may be able to live in only one type of habitat, use only one or a few types of food, or tolerate only a narrow range of climatic and other environmental conditions.

evolutionary divergence

the evolutionary formation of a variety of species (similar to the ancestral) from an ancestral species.


measure of reproductive success.

allopatric speciation

most common mechanism of speciation (especially among animals).

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