unit 4 topic 2 Flashcards
evolution
change in the genetic composition of a population during successive generation, which may result in the development of new species
microevolution
small scale variation of alle frequencies within a species or population, in which the descendant is of the same taxonomic group as the ancestor
macroevolution
major evolutionary change, between species which can lead to things like speciation
evolutionary radiation and mass extinction
evolutionary- an increase in taxonomic diversity that is caused by elevated rates of speciation
mass extinction- short period of geological time in which a high percentage of biodiversity dies out
environmental selection
pressure of environmental selection- the various factors in an environment that has influenced which species in a population are more likely to survive and reproduce
process of natural selection
1.inital genetic variation
2.enviromental pressure are placed on population- external agent from the environment which affect the ability of an organism to survive and be reproductively successful
3. conferring selective advantage
4. change in phenotype and Allee frequence
allele frequency in gene pool
allele frequency- selection pressure can work in Favour of, or against phenotypes and alleles that generate the phenotype
positive selection- selection that Favours the heritable phenotype as a consequence, the allele frequency of the phenotype is likely to increase in the population
negative selection- selection that disfavors that the heritable phenotype as a consequence
phenotypic selection
stabilizing selection - one hill , when an intermediate phenotype is favored as the expanse of both phenotypic extremes
directional selection- short small one, both phenotypic extremes are favored at the expanse of the intermediate phenotypic ranges
disruptive selection
2 bumbs, where both phenotypic extrmes at the expanse of the intermeditae pgentypci ranegs
macroevolutionary change
happens through the processes of mutation, gene flow and genetic drift
mutation- change in the genetic code in DNA can lead to a change in the protein that is coded for a produced by the segment of DNA (gene). these are the only source of new genetic variation for a species
gene flow- the movement of individual into or out of a population as a result of immigration (into) and emigration (out) decreases in an alleles
genetic drift- change in the composition of gene poll as a result of Radom or chance event
bottleneck effect- occurs when natural event reduce population size by order of magnitude
founder effect- when i a small group Bracks away form a larger population to colonies new territory
patterns of evolution
divergent evolution- two species share the same common ancestor
convergent evolution- two unrelated species evolve similar traits independently
parallel evolution- two related species, originate form a common ancestor evolve in similar ways independently after their divergence form each other
coevolution- two or more species effaced each other evolution
modes of speciation
allopatric - when a geographical barrier physical isolates two or more population
parapatric- when sub population are reproductively isolated due to speciating sub-population occupying a new adjacent niche
sympatric- the divergence of species within the same geographical location caused by the reproductive isolation of two population (post- zygotic barrier)
types of isolation
geographic isolation- a physical separation of population of organism form one another decreasing gene flow due to geopgraphical barrers including environmental disaster and habitat fragmentation
reproductive isolation- the inability of a species to breed successfully with related species due to geographical, behavior and genetic barriers overall decrease gene flow as it prevent the exchange of genetic material between population or species
prezygotic isolation- prevent species from mating
postzygotic isolation- occurs after fertilization
how do population reduce genetic diversity
1.starting difference
2.environmental pressures
3. survival advantage
4. more common traits
interpret gene flow
When high rates of gene flow occur between two popultion, the gentic variation between theme decrease thus icnreasintg their homegenity, this means taht the allele frequenceies between each respective popultion become more similar (p) in contrast, alle frequencies will progressively differ across popultion where gene flow have been interrupted. The amount of gene flow occuring can detemine which type of speciation is occuring
