Study Guide

Mechanisms of Evolution Terms

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Mechanisms of Evolution Terms


A characteristic or feature that is maintained by natural selection because it offers a fitness advantage.

Adaptive mutations

Mutations that positively influence an organism's survival.


Different variants of a gene, like the King of Hearts and the King of Diamonds.

Allopatric Speciation

When two species diverge because of geographic boundaries, like a mountain or a wall.

Bottleneck Effect

When a population goes through a very difficult time and not everyone makes it out Alive.


When u c 2 species evolve 2gether. Possibly due to the fact they are BFFs.

Convergent Evolution

The independent evolution of similar structures in different kinds of organisms.

Directional Selection

Selection for one end of a phenotypic spectrum.

Disruptive Selection

Selection for the two ends of a phenotypic spectrum.


A gradual change in genotype that happens over numerous generations that results in a phenotypic change.


The reproductive success of an individual or genotype.

Founder Effect

When a population is started by very few individuals, this effect describes the resulting change on allelic frequencies.

Gene Flow

The movement of genes through a population caused by interbreeding among individuals. There can also be gene flow between populations if migration occurs and is followed by interbreeding. Disruption of gene flow (via reproductive isolation) is required for speciation.

Gene Pool

All the genes, alleles of those genes, and neon-colored swim noodles in a total population.

Genetic Drift

Differences in an allele's frequency due to random events that change the members of a population.

Genetic Equilibrium

When allelic frequencies are unchanging.


Not the type of denim you prefer. Nature can't tell the difference between boot cut and skinny jeans. A genotype is the genetic composition of a living thing that influences a particular trait or phenotype.

Hardy-Weinberg Equilibrium

Assuming no evolution, this equation describes the frequency of a specific allele.


Able to be passed down to offspring.


Evolution happening on a large scale in a larger amount of time on many traits.


Evolution happening on a small scale in a small amount of time on a few traits.


When animals pick up and leave to a new zip code. This is often done regularly, like Snowbirds in Miami Beach.


A change in the DNA sequence.

Natural Selection

The evolutionary process in which individuals that are better adapted to their environment have more offspring than individuals that are not well-adapted to their environment, resulting in greater numbers of well-adapted individuals in the population over several generations.


What you see for a specific trait, which is influenced by both genotype and the environment.

Prezygotic Isolation Barrier

Mechanisms that prevent different species from mating and producing zygotes.


A trait that is influenced by many genes.


More than two sets of chromosomes (more than diploid).


This is a group of interbreeding individuals of the same species. Technically they don't have to actually interbreed; they just have to be able to at some point in their lives. So even though a grandma elephant isn't making baby elephants anymore, she is still part of the population if she lives in the same area as the rest of the herd.

Postzygotic Isolation Barrier

Mechanisms that prevent the zygotes from different species from surviving, becoming adults, and voting. If they do all these things, then they are likely sterile and unable to produce offspring themselves.

Sexual Selection

The evolutionary process in which individuals that have desirable sexual characteristics are more successful at attracting mates.


A group of similar organisms. Members of the same species are able to mate and reproduce. It might be said that Romeo and Juliet should have been two separate species, at least if their parents had anything to do with it.


The evolutionary process by which new species arise from a single evolutionary lineage.

Stabilizing Selection

Selection for the average of the trait, which reduces variety.

Sympatric Speciation

Speciation not caused by physical isolation.

Roots of Common Terms in Mechanisms of Evolution


L = Latin, G = Greek


allos = other (G)


allos = other (G) + patria = homeland (G)


evolvere = unrolling (L)


com = co/with (L) + evolvere = unrolling (L)


genos = born (G) + typos = impression (G)


makros = large (G) + evolvere = unrolling (L)


mikros = small (G)

evolvere = unrolling (L)


Mutare = change (L)


phainein = to show (G) + typos = impression (G)


polys = many (G) + genos = born (G)


polys = many (G) + oid = similar (G)


species = kind (L)


sym = same (G) + patria = homeland (G)

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