Evolutionary mechanisms part 1 Flashcards
evolution
change in allele frequencies over time
evidence of evolutionary change
geology, biogeography, comparative studies of morphology, embryology, and genetics
geology
-fossil records documents continuity in morphological characteristics- evidence of ongoing change in biological lineages
biogeography
-distribution of plants and animals in relation to history of landforms, mountain ranges, and oceans is consistent with evolutionary processes
comparative emrbyology
- early embryos of related species are similar
- reflect common ancestry
- morphological differences appear as embryos develop
comparative morphology
- homologous structures
- reflects common ancestry
- similar embryonic origins, but may have different functions
- human forearm, bat wing
comparative genetics
-comparison of DNA sequences of extant and extinct organisms to address questions about evolutionary relationships
are african or asian elephants more closely related to the extinct wooly mammoth?
asian elephants
-mammoth DNA more similar to asian elephants
mutation
-production of new alleles
rearrangement of existing alleles into new combination via:
sexual reproduction
true or false: more generations= more mutations
true
deleterious mutations
- alter an individual’s structure, function, or behavior in harmful ways
- some are lethal
advantageous mutations
-confer a beneit on individuals that carry it- may increase in frequency
neutral mutations
neither harmful nor helpful
do mutations happen because an individual/ species/ population “needs” them to deal with some specific problem?
no! mutations arise randomly with respects to needs
does sexual selection generate new alleles?
no! but it generates new combos of alleles through crossing over and random fertilization
quantitative variation
traits that vary along a continuum
-height
qualitative variation
either you have the trait or you dont
hardy weinberg principle
- model that specifies conditions in which allele frequencies would NOT change and a population would be at genetic equilibrium
- it specifies the conditions in which evolution would not occur
genetic equilibrium is possible only if all of the following conditions are met in a population
- no mutations are occurring
- the population is closed to migration
- the population is infinite in size
- all genotypes survive and reproduce equally well
- individuals mate randomly with respect to genotype
- natural populations never meet all 5 requirements
relative fitness
number of surviving offspring that an individual produces compared with others in the population
examples of evolution by natural selection
- pesticide (mosquitoes and DDT)
- coat coloration in oldfield mice
gene pool
all the genes, or genetic information in any population
product
an adaptive trait is any product of natural selection that increases the relative fitness of an organism in its environment
process
adaptation is the accumulation of adaptive traits over time
adaptation s come in 2 general forms
physical and behavioral
physical adaptation
camouflage, hair, large ears, flashy plumage
behavior adaptation
group living, migration, hibernation, brood parasitism, defensive posture
directional selection
occurs when individuals near one end of phenotypic distribution are favored
-shifts mean value for the trait away from the existing mean and toward the favored extreme
stabilizing selection
occurs when individuals expressing intermediate phenotypes are favored- it eliminates phenotypic extremes
-reduces variation, but does not change the mean value of a trait
disruptive selection
favors extreme phenotypes over intermediate phenotypes
- ex. small and large beak size in black bellied seed crackers - alleles producing extreme phenotypes become more common, promoting discrete traits
why doesn’t natural selection produce perfect organisms?
- can only act on existing variation in a population
- has to work within the bounds of universal physical and chemical constraints
- any adaptations usually require compromises (tradeoffs) among different traits
natural selection acts on ____ of _____, but ______ is change in allele frequencies (______)in a _______ over time
phenotypes, individuals, evolution, genotypes, population
