evolution Flashcards
(24 cards)
what are the central ideas of evolution
all life has history
the history changed over time
diff species share common ansestor(s)
what are the three mechanisms for evolutionary change
natural selection
genetic drift
gene flow
what is natural selection
theory from darwin
not all indiv reproduce, menaing that reproductive success of indiv in pop varies.
the notion that individuals who are better adapted to their environment will have a greater chance for reproductive success
how does evolution occur
by natural selection
what is required for natural selection to occur
variation in a population
(physical, phisiological or behavioural)
diff in reprod success
heritable traits
what are adaptations
traits that are important for survoval and report to specific environ conditions
what is fitness
the ability for an indiv to contribute to the next generation of a population
what is natural selection
the differential survival and repro of individuals due to the environment acting on the inherited traits
not random!
what is evolution
the intergeneration change in allele frequences in a population
what are alleles
different versions of the same gene and are responsible for phenotypic variations
wht are phenotypes
the physical expression of an orgs genotype
observable traits
what is heritability
the ability for genes to be passed form generation to generation
measured by h^2=VG/VP or VG/(VG+VE)
perfectly heritable trait vs not heritable
perfect: when h^2= 1.0
all pheo variation is due to genetic diff
not heritable: all pheno variation is due to environmental factors
note that in most cases this is in a mix
when may mutations contribute to evolution?
when sex cells orgametes are mutated
what are mutations
random events that cause for a change in the genetic code. may provide an advantage, disadvantage or neutral effects.
what is phenotypic plasticity
variation of an organism’s form due to an environmental (only) influence
will happen rapidly and may be adaptive if the expressed genotype increases ecological performance
what is trait evolution
evolution that occurs on a shirt times scale, commonly acting on the phenotypes that currently exists in the environ
what are the three modes of natural selection
stabilizing
directional
disruptive
what is stabilizing selection
intermediate phenotypes are favored while extremes have lower reproduction rates and survival rates
extreme phenotypes are rare
what is directional selection
one extreme phenotype has a higher fittness on a pop. intermediate and the other extreme pheno have low fitness
the population will shift over time to express the extreme pheno (move is a single direction)
what is disruption selection
when the 2 extreme phenotypes have the higher fitness. intermediate phenotypes have lower reproduction and survival rates
a bimodal distribution will form in the population
how does the environment influence phenotype
during the primal development stages, some orgs require to be exposed to specific environmental factors such as a song or food type in order to adapt the trait or quality later on in life. if the factor that delivers this trait is altered or changed, it may interfere with the reproductive success (identity) of the indiv in the future.
what is genetic drift
the random change in allele frequencies in a population
what is gene flow
the movement of gene in or out of a population
