Chapter 20

Front 1

Biological Species concept

Back 1

latin=kind one or more populations whose members are capable of interbreeeding in nature to produce fertile offspring and do not interbreed with members of other species

Front 2

Evolutionary species concept

Back 2

aka phylogenetic species concept. an alternative to the biological species concept in which for a population to be declared a separate species, it must have undergone evolution long enough for statistically significant differences to emerge.

Front 3

reproductive isolating mechanisms

Back 3

prevent interbreeding between two different species whose ranges( habitats) overlap. preserves the genetic integrity of each species, because gene flow between the two species is prevented.

Front 4

characteristics of reproductive isolation

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-most mechanisms occur before mating or fertilization occurs
-prezyotic barriers interfere with fertilization
-postzygotic barriers prevent gene flow when fertilization occurs
-biologist are discovering the genetic basis of isolating mechanisms

Front 5

prezygotic barriers

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are isolating mechanisms that prevent fertilization from taking place. b/c male and female gametes never come into contact an interspecific zygote- afertilized egg formed by the union of an egg from one species and a sperm from another species is never produced

Front 6

temporal isolation

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a prezygotic reproductive isolating mechanism in which genetic exchange is prevented between similar species because they reproduce at different times of the day, season, or year.

Front 7

habitat isolation

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a prezygotic reproductive isolating mechanism in which reproduction between similiar species is prevented because they live and breed in diffrent habitats

Front 8

behavioral isolation

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a prezygotic reproductive isolating mechanisms in which reproduction between similiar species is prevented because each group exhibits its own characteristic courtship behavior aka sexual isolation

Front 9

mechanical isolation

Back 9

a prezygotic reproductive isolating mechanism in which fusion of the gametes of two species is prevented by morphological or anatomical diffrences

Front 10

gametic isolation

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a prezygotic reproductive isolating mechanism in which sexual reprodcution between tow closely related species cannot occur because of chemical diffrences in gametes

Front 11

postzygotic barriers

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one of several reprodcutive isolating mechanisms that prevent gene flow between species after fertilization has taken place hybrid sterility inviablitlity and hybrid breakdown

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development

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all the progressive changes that tkae place throughout the life of an organism

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hybrid inviability

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a postzygotic reproductive isolating mechanism in which the embryonic development of an interspecific hybrid is aborted.

Front 14

hybrid sterility

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a postzygoti reproductive isolating mechanism in which an interspecific hybrid cannot reproduce successfully

Front 15

hybrid breakdown

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a postzygotic reproductive isolating mechanism in which although an interspecific hybrid is fertile and prodcues a second generation, the f2 has defects that prevent it from successfully reproducing.

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speciation

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evolution of a new species

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speciation characteristics

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-long physical isolation and diffrent selective pressures reslult in alllopatric speciation
-two populations diverge in the same physical location by sympatric speciation
-allopolyploidy is an important mechanism of sympatric spectiation in plants
-changing ecology causes sympatric speciation in animals
-reproductive isolation breaks down in hybrid zones

Front 18

allopatric speciation

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occurs when one population becomes geograhrically sperated from the rest of the species and subsequently evolves by natural selection and or geneti drift

Front 19

subspecies

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taxomic subdivion of a species

Front 20

sympatric speciation

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a new species evolves within the same geographic region as the parental species. common inn plants. it occurs in two ways change in ploidy and ecology

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ploidy

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the number of chromosme sets making up an organism's genome

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polyploidy

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the possesion of more than two sets of chrmosomes is a mjaor factor in plant evolution

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autopolyploidy

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contains multiple sets of chromosomes from a single species

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allopolyploidy

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contains multiple sets of chromosmes from two or more species.

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hybridiazation

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allopolyploidy occurs in conjunction

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`sexual selection

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charles darwin called chooosing a mate base on its color sexual selection

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endemic

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localized, native species that are not found anywhere else in the world.

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hybrid zone

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an area of overlap between two closlely related population, subspecies, or species in which interbreeding occurs

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punctuated equillibrium

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the idea that evolution proceeds with period of little or no genetic change, flowed by very active phases so that major adaptations or cluster of adaptations appear suddenly in the fossil record.

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stasis

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long long periods in the fossil record in which there is little or no evolutionary change

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gradualism

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the idea that evolution occurs by a slow, steady accumulation of genetic changes over time.

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macroevolotuon

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large scale phenotypic changes in opulation that warrant their placcement in taxonomic groups at the species level and higher

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preadaptaions

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pre-existing structures

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allometric growth

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development most organisms exhibit varied rates of growth for diffrent parts of the body.

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paedomorphosis

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juvenile characteristics were retained in the adult stage

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adaptive radiation

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evolutionary diversification of many related species from one or a few ancestral species in a relatively shor period

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adaptive zones

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new ecological opportunities that were not exploited by an ancestral organism

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background extinction

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continuous low level exctinction of species

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mass extinctions

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numerous species and highter taxonomic groups have taken place in both terrestrial and marine environments

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modern synthesis

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or synthetic theory of evolution, in which mutation provides the genetic variation on which natural selection acts