Evolution General Zoology, 19 January 2011 Donald Winslow Reading: Hickman et al Integrated Principles of Zoology, 15 th ed., McGraw-Hill Ch. 1 pp 13-15; Ch. 6 pp , , “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 developed theory 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 individualsCopies of TCopies of t T/TT/T20400 T/tT/t t/tt/t p = frequency of T = 80/200 = 0.4 q = 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)