Forces of Evolution Flashcards
two major developments of understanding evolutionary synthesis
mendels theory of heredity
darwins theory of evolution
mendels theory of heredity
discrete units of information (genes) are passed unchanged from generation to generation
modern synthesis of evolution
- it is the production and redistribution of variation (inherited differences among organisms)
- natural selection acts on this variation causing inherited differences among individuals to affect their ability to successfully reproduce
current definition of evolution
a change in allele frequency from one generation to he next
allele frequencies are indicators of…
the genetic makeup of a population, the members of which share a common gene pool
allele frequences refer to the…
percentage of all the alleles at a locus accounted for by one specific allele
microevolution
small genetic changes that occur within a species, even just from one generation to the next
example of microevolution in humans
different ABO blood types
macroevolution
large scale changes that occur in populations after many generations, such as the appearance of a new species
speciation
appearance of a new species
5 factors that produce and redistribute variation, allowing for evolution
mutation gene flow genetic drift and founder effect recombination natural selection
mutation
molecular alteration in genetic material
for a mutation to have evolutionary significance it must occur in a
gamete
mutation rates for any given trait are usually
low
what is the only way to produce new genes
mutation
if mutation offers an advantage or disadvantage, when combined with natural selection evolutionary changes can occur
more and more rapidly
gene flow
the exchange of genes between populations
gene flow is a consistant feature of
human evolution
human examples of gene flow
offspring of US soldiers and vietnamese women
when individuals move temporarily and mate in a new population they dont necessarily
stay there
flow of genes is characterized by
gradual distribution
exogamous
individuals marry outside of some cultural/ genetic group
endogamous
individuals marry inside of some cultural/genetic group
exagamous relationships result in…
higher genetic diversity, more gene flow
patrilocal
males remain in birthplace, females migrate
low Y chromosome diversity
high mt DNA diversity
mt DNA is given by
mother
matrilocal
females remain in birthplace and males migrate
high Y diversity, low mt diversity
matrilocal and patrilocal populations are both examples of
sex specific gene flow
genetic drift
the effects of random chance on gene frequencies in a population- alleles can be reduced or eliminated by the loss of a few members of a group
genetic drift only has an effect on
small populations
why is genetic drift important to human evolution
for most of human history we have lived in very small populations that would be vunerable to genetic drift
founder effect is a type of
genetic drift
founder effect
occurs when a small band of founders leaves its parent group and forms a colony elsewhere, a new population is established and all members are descended from founders
a once rare allele carried by founders can eventually become common
example of genetic drift and the founder effect
native american population having lots of blood type O , no B and very little A
natural selection provides
a directional change in allele frequency relative to specific environmental factors
if the environment changes…
selection pressures also change
if there are long term environmental changes in a consistent direction, then allele frequencies should also…
shift gradually each generation
natural selection example
sickle cell and malaria
being heterozygous for sickle cell gives malarial resistance, thus in areas where malaria is present (africa) sickle cell si also more present as ut is advantageous to be heterozygous for the malarial resistance
balanced polymorphism
selection for heterozygotes of sickle cell for increased malarial resistance
non random mating is an important factor in
human breeding practices
humans mate in a ____________ way
non random
human selection for social and physical traits effect
allele frequencies
