Introduction to Darwinian Evolution

Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition

Solomon • Berg • Martin

Chapter 17

Introduction to Introduction to Darwinian EvolutionDarwinian Evolution



CHAPTER 17 Introduction to Darwinian Evolution

• Terminology• Evolution

–Accumulation of inherited changes within populations over time

• Population–Group of individuals of one species that live in

the same geographic area at the same time

• Species–Group of organisms with similar structure,

function, and behavior capable of interbreeding




• Pre-Darwinian ideas • Aristotle (384–322 B.C.E.)

–Saw evidence of natural affinities

• Leonardo da Vinci (1452–1519)–Correctly interpreted fossil rocks

• Jean Baptiste de Lamarck (1744–1829)–First to propose that organisms undergo

change as a result of natural phenomenon–Lamarck ideas discredited when Mendel’s

theories rediscovered around 1900




Darwinand evolution




• Voyage of the H.M.S. Beagle• 1831• Basis for Darwin’s theory of evolution• Darwin observed similarities between

animals and plants–Arid Galapagos Islands–Humid South American mainland




Voyage of the H.M.S. Beagle




• Influences on Darwin• Principles of Geology by Lyell• Artificial selection

–Breeders developing many varieties of domesticated animals in a few generations

–Plant varieties, such as kale and broccoli, developed from wild cabbage

• Ideas of Thomas Malthus–Population growth not always desirable–Population increases geometrically; food

supply increases arithmetically




Artificialselection inchickens:“Big Bird”




Artificialselection inBrassicaoleracea




• Evolution occurs by natural selection• Adaptation

–Inherited variations favorable to survival persevere

–Unfavorable variations are eliminated




Genetic variation in emerald tree boas




• Theory of evolution by natural selection• Proposed by both Darwin and Wallace• Based on four observations

–Genetic variation exists among individuals–Reproductive ability of species causes its

populations to geometrically increase–Organisms compete for resources–Offspring with most favorable

characteristics is most likely to survive




• Synthetic theory of evolution• Began in 1930s and 1940s• Combines principles of Mendelian

inheritance and natural selection–Mutation provides genetic variability on

which natural selection acts–Incorporates expanding knowledge in

genetic, systematics, and other scientific fields




Wing size in female fruit flies




• Evidence for evolution from fossil records• Direct evidence of evolution comes from

fossils• Evidence shows progression from

earliest unicellular organisms to organisms of today

• Shows life has evolved through time




Exposed layersofsedimentaryrock




Fossils developin differentways




Fossilintermediatesin whale evolution




Determiningthe ageof fossils:radioisotopedecay




• Evidence for evolution from comparative anatomy• Homologous features

–Derive from same structure in common ancestor

• Homoplastic features–Similar functions in distantly related organisms

demonstrates convergent evolution

• Vestigial structures–Remnants of structures indicating adaptation




Homology in animals




Homology in plants




Homoplasy




Convergent evolution: mammals who eat ants and termites




Vestigial structures




• Biogeography• Study of past and present geographic

distribution of organisms• Continental drift has played a major role in

evolution




Continental drift




• Evidence for evolution from developmental biology• Proteins and DNA contain record of

evolutionary change• Phylogeny

–Evolutionary history of group of related species

• Phylogenetic trees–Diagrams showing lines of descent based on

molecular data




Phylogenetictree ofwhales andtheir closestliving relatives




• Evolutionary hypotheses tested experimentally• Reznick and Endler• Differences in predation correlated with

differences in guppies–Male coloration and behavior–Life history traits




Experimentalevidenceofnaturalselectionin guppies

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Introduction to Darwinian Evolution