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)