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EvolutionGeneral Zoology, 19 January 2011
Donald Winslow
Reading: Hickman et al. 2011 Integrated Principles of Zoology,
15th ed., McGraw-HillCh. 1 pp 13-15;
Ch. 6 pp 101-109, 111-121, 123-131
“Nothing in biology makes sense except in the light of evolution.” --Theodosius Dobzhansky
Founders of evolution Lamarck—inheritance of acquired traits Lyell—uniformitarianism & gradualism Malthus—exponential growth & limitation Darwin—natural selection, speciation Wallace—independently developedtheory of evolution by natural selection& inspired Darwin to publish.
Darwin's theory of evolution
Change
Common descent
Speciation
Gradualism
Natural selection
Charles Darwin Voyage on H.M.S. Beagle, Galapagos Natural selection & adaptation
Population growth & limits to growth Competition and heritable variation Differential survival & reproduction Gradual adaptation & speciation
Reproductive barriers & speciation
Evidence for evolution Fossil record
Marine organisms on mountaintops Geological time & dating—isotope decay Evolutionary trends—horses Homology of vertebrate forelimbs (Fig 6.14) “Ontogeny recapitulates phylogeny.”
- Ernst Haeckel
Flying Great Egret (Ardea alba). Photo by Karen Bays.
Bird wings are homologous to a human’s arms.
Ontogeny & phylogeny
Pharyngeal gill slits– Present in fish, reptiles, birds, mammals
Paedomorphosis– Axolotls—salamanders that never grow up
Heterochrony– Change in the timing of development
Microevolution
Population genetics Gene pool Allele frequencies Hardy-Weinberg equilibrium
Allele frequencies
Example with allele (T) for ability to taste phenylthiocarbamide (from Hickman, et al.)
Genotype # of individuals Copies of T Copies of t
T/T 20 40 0
T/t 40 40 40
t/t 40 0 80
100 80 120
p = frequency of T = 80/200 = 0.4q = frequency of t = 120/200 = 0.6
Forces that change allele frequencies
Mutation Genetic drift Nonrandom mating—e.g. assortative mating Migration Selection (natural, artificial, sexual)
Relative fitness Stabilizing, directional, & disrupting selection
Bright plumage of male Northern Cardinal—
A result of sexual selection.
Measuring genetic variation Protein polymorphism & heterozygosity Gel electrophoresis Quantitative characters
Dark-eyed Junco (Junco hyemalis) color variants
Leucistic “Purple” Finch(Carpodacus purpureus)
Macroevolution Allopatric & sympatric speciation Hybridization, extinction Adaptive radiation (diversification) Gradualism, punctuated equilibrium Mass extinction Levels of selection
Genic, individual, kin, group, species
Eastern Meadowlark (Sturnella magna)