Ecology and Evo
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which scientists argued for continuous distribution of traits
darwin, f. galton, K. pearson
dominant trait what is the genotype and phenotype ratios
organism can pass on characteristics that it acquired during its lifetime to its offspring.
sudden change from one generation to the next
mutation is good or bad
survival is the perpetual struggle for food and room
Darwin went to what school
Dr. Butler's school, strictly classical
almost took Darwin's position on the Beagle
when was the voyage of the Beagle
Dec 1831-Oct 1836
alfred russel wallace
came to same conclusions as Darwin on the origin of species
what was the problem of blending inheritance?
natural selection would not work if the extremes are eliminated...need a particular form of inheritance that does not lose extremes
who advocated the cell theory of 1839
weismann, johannsen, morgan
est. population genetics
what is population genetics
study of distribution and changes in allele frequency in a population as it is subject to selection, genetic drift, mutation and genetic recombination
what was the reconciliation between the mendelians and the biometricians
polygenics: phenotype is influenced by more than one gene
what are the assumptions of hardy-weinberg relation?
- random pairing, no assortative mating
- no selection
- no migration
why is H-W an equilibrium?
the new frequency is the same as the old frequency
what does HW ensure?
- maintenance of genetic variation
- translation between allele and genotype frequencies
- provides evidence of evolutionary action when genotype frequencies deviate
how does variation occur?
through mutation and recombination (reshuffles mutations in new configurations)
can mutation drive evolution?
too infrequent, cannot itself drive evolution
how is the fate of variation determined?
by both stochastic (genetic drift, random) and deterministic (natural selection). The latter leads to adaptation.
natural selections acts on who, what are its consequences?
acts on individuals, but consequences are populational
sources of genetic variation?
- non-disjunction (meiotic anomalies)
- mutations: DNA rep errors
- recombinations (mutations shuffled into new configurations)
how to measure genetic variation?
- mendelizing morphological or serological traits
- chromosomal variation
- protein variants
- restriction mapping
- DNA sequence
what is the paradox at heart of darwinism
mutations are bad for individuals but required for evolution
robins laying eggs is what kind of selection?
peppered moth vs. dark moths what kind of selection?
two alleles at 1 locus
what percentage of human genome encodes proteins?
what percent of human genes are in the mouse
are we more homologous to fruit fly or nematode worm?
- fruit fly (61% of homologous proteins) vs 43%
- half a billion years of evolutionary separation from humans
how to do functional tests of similarity?
- eyeless drosophila is the homolog of pax-6 in mammals
- inject rat gene for eye, drosophila grows eye
birth weight is what kind of selection?
- increase in frequency of the intermediate phenotype
synonymous evolution, which is faster?
- silent mutations
- synonymous mutation is faster than non synonymous
who performed experiments on peppered moth?
DNA doesn't change
- independent evolution of similar features in species of different lineages.
- creates analogous structures with similar form or function, but not present in last common ancestor of those groups
who did experiments with blind cavefish (astyanax mexicanus)
after the drought, what kind of beaks were the best?
bigger beaks, because the size and hardness of the seeds increased.
- can't see color
- affected 5% of population in micronesia, ping clap
rate of change of gene frequency by random drift depends on what?
size of the population
who did research on the lynx and the hare
e t seton
effective population size
- when drift has no significant effect; population has the same magnitude of genetic drift as the actual population
- in fluctuating populations, N is the harmonic mean of the population size
random walk whose transition is dependent only on its position in the previous step
in absence of selection gene frequencies vary until population is fixed (0 or 1 for an allele)
who came up with neutral theory of evolution, when?
motoo kimura 1968
what does kimura propose?
- most mutations are neutral
- immediately goes to zero frequency if the mutation is neg
- rarely positive (goes to fixation)
- so population size does not matter
what does the total extent of genetic divergence depend on?
time since isolation
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