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