Evolution

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microevolution

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the changes in a single gene pool

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macroevolution

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refers to the appearance of a major evolutionary development or a new species

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anagenesis (phyletic evolution)

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occurs when one species replaces another

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cladogenesis (branching evolution)

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occurs when a new species branches out from a parent species

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by studying fossil records, paleontology reveals....

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the existance of species that have become extinct or have evolved into other species

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homologous structures

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have a common origin and reflect a common ancestry

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analogous structures

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have the same function, NOT because of a common ancestor

(bat's wing and a fly's wing)

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vestigial structures

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evidence that structures have evolved
-not needed for an organism to survive

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the theory of continental drift

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states that about 200 million years ago, the continents were locked together in a single supercontinent known as Pangea

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Cuvier

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studied fossils and realized that each stratum of earth is characterized by different fossils
-CATASTROPHISM
-influenced Darwin

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catastrophism

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catastrophes were responsible for the changes in the organisms on earth

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James Hutton

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-GRADUALISM

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gradualism

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earth has been molded, not by sudden, violent events, but by slow, gradual change

-effects of wind, weather, and the flow of water contribute to gradualsim

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Lyell

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-great influence on Darwin
-stated that geological change results from slow, continuous actions
-believed the earth was more than 6,000 years old

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Lamarch

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-inheritance of acquired characteristics
-use and disuse

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Darwin's theory of evolution

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1) populations tend to grow exonentionally, overpopulate, and exceed their resources
2) overpopulation results in competition and a struggle for existance
3) in any population, there is variation and an unequal ability of individuals to surviv and reproduce
4) only the best-fit individuals survive and get to pass on their traits to offspring
5) evolution occurs as advantageous traits accumulate in a population

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stabilizing selection

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eliminates the extremes and favors the more common intermediate forms

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disruptive selection

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increases the extreme types in a population at the expense of intermediate forms

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directional selection

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one phenotype replaces another in a gene pool

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sexual selection

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based on variation in secondary sexual characteristics related to competing for and attracting mates

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sexual dimorphism

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differences in appearance between males and females

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artificial selection

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when humans breed plants and animals by seeking individuals with desired traits

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_____in a population is necessary in order for a population to evolve as they environment changes

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variation

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balanced polymorphism

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the presence of 2 or more phentoypically distinct forms of a trait in a single population of a species

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north-south cline

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variation due to differences in northern and southern environments

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outbreeding

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the mating of organisms within one species that are not closely related

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sources of variation in a population

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1) geographic variation
2) sexual reproduction
-independent assortment
-crossing over
- random fertilization
4) outbreeding
5) blood type

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causes of evolution of a population

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1) genetic drift
2) gene flow
3) mutations
4) nonrandom mating
5) natural selection

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genetic drift

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change in the gene pool due to chance
-fluctuation in frequency of alleles from one generation to another
-unpredictable
-tends to LIMIT diversity

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bottleneck effect

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when natural disasters, reduce the size of a population unselectively, resulting in the loss of genetic variation

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founder effect

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when a small population breaks away from a larger one to colonize a new area.
-rare alleles may be overrepresented

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polydactyly

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having extra toes or fingers

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gene flow

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the movement of alleles into or out of a population

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nonrandom mating

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individuals choose their mates for a specific reason
-selection of a mate serves to eliminate the less-fit individuals

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natural selection

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those individuals who are better adapted in a particular environment exhibit better reproductive success

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hardy weinberg described a

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stable, nonevolving population

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according to hardy-weinberg, if the population is stable, the following must be true

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1) population must be large (in a small population, the smallest change in the gene pool will have major effects in allelic frequencies)
2) population must be isolated from other populations (no migration of organsims in or out of the gene pool becuase that could alter frequencies)
3) there must be no mutations in the population (a mutation could cause a change in allelic frequencies by introducing a new allele)
4) mating must be random (if individuals select mates, then those individuals that are better adapted will have a reproductive advantage and the population will evolve)
5) no natural selection (natural selection causes changes in relative frequencies of alleles in a gene pool)

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p stands for

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dominant allele

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q stands for

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recessive allele

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speciation

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when interbreeding between 2 populations does not take place any more because they have diverged so much

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allopatric speciation

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-caused by geographic isolation
-the formation of new species caused by geographic barriers

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polyploidy

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the condition where a cell has more than 2 complete sets of chromosomes

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habitat isolation

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2 organisms live in the same area but encounter each other rarely

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behavioral isolation

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different species have different behaviors that will not attract ofther species

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temporal selection

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reproductive isolation due to different mating seasons, times, etc

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reproductive isolation

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-difference in genitalia
-difference in flower shape

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prezygotic barriers

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things that prevent mating

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postzygotic barriers

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things that prevent the production of fertile offspring, once mating has occurred

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divergent evolution occurs when

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a population becomes isolated from the rest of a species, becomes exposed to new selective pressures, and evolves into a new species

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gradualism

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the theory that organisms descend from a common ancestor gradually over a long period of time

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punctuated equilibrium

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a theory that proposes that new species appear suddenly after long periods of stasis

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the ancient atmosphere lacked

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oxygen