Evolution - Gradualism and Punctuated Equilibrium, Evolution Definition

Who proposed the term "punctuated equilibrium"?

Niles Eldredge and Stephen Jay Gould

When does punctuated equilibrium occur?

Rapid change occurs when a smaller population of species are isolated from the parent population

What does evolutionary fitness relate to?

Reproductive success.

What happens in a large population?

Lower evolutionary rate, more likely to appear on the fossil record

Approximately how long does it take for gradualism to occur?

Millions of years

diversity

all of the different species on Earth

genetic drift

change in allele frequencies of a population due to chance or random events rather than by natural selection

evolution

change in variation over time; process by which modern organisms have descended from ancient organisms (decent with modification)

genetic/inherited traits

characteristics of a species passed down from parent to offspring (babies)

acquired traits

characteristics that an organisms gets during their lifetime. They are not genetic and can not be passed on.

Struggle for existance

competition to survive, not all of a species will survive

stabilizing selection

form of natural selection that occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end

geographic isolation

form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water

behavioral isolation

form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding

species

group of similar organisms capable of interbreeding and producing fertile offspring

adaptation

inherited characteristic that increases an organism's chance of survival

analogous structures

is a trait or an organ that appears similar in two unrelated organisms

gene flow

is the transfer of alleles or genes from one population to another

overproduction

more will born than can survive

natural selection

natures way of selecting the best a particular environment; also called survival of the fittest

allele frequency

number of times an allele occurs in a gene pool

punctuated equilibrium

pattern of evolution in which long stable periods (stasis) are interrupted by brief periods of rapid change

divergent evolution (adaptive radiation)

process by which a single species or small group of species evolves into several different forms that live in different ways

homologous structures

structures that have different mature forms in different organisms but develop from the same embryonic tissues; evidence of common ancestry

Theory of Evolution

the best scientific explanation for both the unity and diversity of life; proposed by Charles Darwin

variation

the differences within a single species

fossil record

the geological record of organisms on earth that have been preserved in the rock in a chronological order (oldest on bottom); evidence of common ancestry

reproductive isolation

the inability of a species to breed successfully with related species due to geographical, behavioral, physiological, or genetic barriers or differences

gene pool

the sum of all the genes in an interbreeding population

single-gene trait

trait controlled by a single gene (ex: widow's peak in humans)

polygenic trait

trait controlled by two or more genes (ex: skin color of humans)

Charles Darwin

wrote the book on the theory of Natural Selection

Population

• Groups of interbreeding organisms in the same area

speciation

formation of new species

Gradualism

Change that is incremental and slow that happens over time

Evolutionary fitness

Contribution of an individual to the gene pool of the next generation based on that individual's phenotype or genotype.

What happens in a small population?

Easier for evolution, higher evolutionary rate

Punctuated Equilibrium

Evolution is slow and it is interrupted by periods of rapid change

What are the two main ways to describe the rate of evolutionary change?

Gradualism and Punctuated Equilibrium

How is evolutionary fitness determined?

How many offspring you can produce that will survive and pass on your traits. (N/2)

Approximately how long does it take for punctuated equilibrium to occur?

Hundreds of thousands of years

Subspecies

In biological classification, the term subspecies refers to a unity of populations of a species living in a subdivision of the species's global range and varies from other populations of the same species by morphological characteristics. A subspecies cannot be recognized independently. A species is either recognized as having no subspecies at all or at least two, including any that are extinct.

Natural Selection • Populations will reflect the collective group of adaptations best suited to their environment • Most traits are polygenic • 4 types of polygenic selection

Stabilizing Selection Eliminates extreme phenotypes Directional Selection • Favors one extreme over the other Disruptive Selection • Favors both extremes Sexual Selection • Based on the ability to attract a male • Sexual Dimorphism: Males and females of the same species do not look the same - Males generally have to attract their mates

artificial selection (selective breeding)

When human get to decide that characteristics will survive in a population. ex. domestic dogs

common ancestry

a group of organisms share common descent if they have a common ancestor

vestigial structure

a structure that an organism has that is no longer useful to it, but that they have this structure because a common ancestor to that organism found it useful