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BIOL 1202, Section 1 Dr. Kyle Harms Course website: http://www.biology.lsu.edu/webfac/kharms/BIOL1202Fall2007.htm http://www.biology.lsu.edu/webfac/kharms/BIOL1202Fall2007.htm In BIOL 1202, good attendance pays off! Proportion of students Final exam score Chapter 22

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BIOL 1202, Section 1

Dr. Kyle Harms

Course website:

http://www.biology.lsu.edu/webfac/kharms/BIOL1202Fall2007.htm

http://www.biology.lsu.edu/webfac/kharms/BIOL1202Fall2007.htm


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In BIOL 1202, good attendance pays off!

Proportion of students

Final exam score


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Chapter 22

Descent with Modification:

A Darwinian View of Life


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Why are there so many species?


The theory of evolution by natural selection charles darwin l.jpg

The Theory of Evolutionby Natural SelectionCharles Darwin


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Hypothesis vs. Theory


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Hypothesis

Tentative explanation of

observations

Educated guess


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Theory

General explanation of important natural phenomena, developed through extensive & reproducible observations & experiments


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Western Historical Context

Species are permanent, perfect, immutable

Aristotle (384-322 B.C.) – Greek philosopher

Dominant world view for > 2000 yr

See timeline Fig. 22.2


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Western Historical Context

A.D. – Natural Theology (Creationism)

Species are permanent, perfect, immutable

See timeline Fig. 22.2


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Western Historical Context

Carolus Linnaeus (1707-1778)

Swedish physician & botanist whose passion was taxonomy

Developed a hierarchical classification scheme & binomial nomenclature

See timeline Fig. 22.2


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Western Historical Context

Carolus Linnaeus (1707-1778)

Canis = genus

lupus = specific epithet that refers to one species in the genusCanis

The binomial is always italicized or underlined, the genus name is always capitalized, and the specific epithet is always lower case

“King Philip Came Over For Gumbo Sunday”

See Fig. 25.8


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Western Historical Context

Georges Cuvier (1769-1832)

French anatomist who largely developed paleontology, the study of fossils

See timeline Fig. 22.2


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Western Historical Context

Georges Cuvier (1769-1832)

Deeper strata contain older taxa

See timeline Fig. 22.2


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Western Historical Context

Georges Cuvier (1769-1832)

Preferred hypothesis for profound geologic change = catastrophism

See timeline Fig. 22.2


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Western Historical Context

James Hutton (1726-1797)

Scottish geologist who offered an alternative to catastrophism

Preferred hypothesis for profound geologic change = gradualism

See timeline Fig. 22.2


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Western Historical Context

Charles Lyell (1797-1875)

Scottish geologist who incorporated Hutton’s gradualism into the theory of uniformitarianism

See timeline Fig. 22.2


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Western Historical Context

Charles Lyell (1797-1875)

Uniformitarianism – geological processes & rates today are those that also operated in antiquity

See timeline Fig. 22.2


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Western Historical Context

Charles Lyell (1797-1875)

Uniformitarianism – suggested that the Earth is > 6000 yr old

See timeline Fig. 22.2


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Western Historical Context

Jean Baptiste Lamarck (1744-1829)

Invertebrate Curator ofthe Natural History Museum in Paris

One of the 18th & 19thcenturies’ biologists who hypothesized that traits of species are not immutable, i.e., they can evolve

See timeline Fig. 22.2


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Western Historical Context

Jean Baptiste Lamarck (1744-1829)

Hypothesized mechanism of evolution: Use & disuse alters traits; inheritance of acquired characters results in adaptations to environmental conditions

See timeline Fig. 22.2


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Western Historical Context

Thomas Malthus (1766-1834)

English demographer

Hypothesis: Plants and animals are capable of producing far more offspring than resources can support; the “struggle for existence” (e.g., famine, war) is an inescapable consequence

See timeline Fig. 22.2


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Western Historical Context

England

EUROPE

NORTH

AMERICA

ATLANTIC

OCEAN

PACIFIC

OCEAN

Galápagos

Islands

HMS Beagle in port

AFRICA

SOUTH

AMERICA

Darwin in 1840,

after his return

AUSTRALIA

Cape of

Good Hope

Andes

Tasmania

Cape Horn

New

Zealand

Tierra del Fuego

Within this context, Charles Darwin(1809-1882)served as Ship’s Naturalist on the HMS Beagle’s circumnavigation of the globe (1831-1836)


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Galapagos Islands, Ecuador


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Galapagos Islands, Ecuador


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Galapagos Islands, Ecuador


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Galapagos Islands, Ecuador


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Darwin was a good observer of both wild and domesticated organisms (e.g., birds)


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Darwin was a good observer of both wild and domesticated organisms (e.g., birds)


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Western Historical Context

Charles Darwin (1809-1882)

English gentleman who conceived of natural selection as the principal mechanism of adaptive evolution

See timeline Fig. 22.2


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Western Historical Context

Alfred Russel Wallace (1823-1913)

English biologist who also (independently) conceived of natural selection as the principal mechanism of adaptive evolution

See timeline Fig. 22.2


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Western Historical Context

Lyell presented the independently derived hypothesis to the Linnaean Society of London on July 1, 1858


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Western Historical Context

Charles Darwin (1809-1882)

The Origin of Species

(1859)


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The Origin of SpeciesFinal paragraph:

“It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us…

There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”


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Darwinian Theory of Evolution

Descent with modification

Descent implies common ancestry

Modification to better suite the environment = adaptation

Natural selection is the principal process that drives adaptive evolution

See Fig. 22.7


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Darwinian Theory of Evolution

Organisms have enormous potential for population increase, but the potential is rarely reached

Generalized sigmoidal population growth curve


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Potential for rapid population

growth when resources

are not limiting

Resource availability generally limits population size

Competition for resources

(“struggle for existence”)

Phenotypic variability (morphology, physiology, behavior, etc.)

Natural Selection: Survival and reproduction of the “fittest” individuals

Some variabilityresults from heritable differences

Adaptive evolution: A change in the phenotypic constitution of a population owing to selection on heritable variation among phenotypes


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Lamarckism

Inheritance of

acquired

characteristics

Use

Darwinism

Genetic

inheritance from selected population

Natural

selection

Generation 2

Generation 1


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Evidence for the Theory of Evolution by Natural Selection

Darwin used artificial selection to illustrate the modifying potential of selection


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Evidence for the Theory of Evolution by Natural Selection

Darwin used artificial selection to illustrate the modifying potential of selection


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Evidence for the Theory of Evolution by Natural Selection

Darwin used artificial selection to illustrate the modifying potential of selection


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Evidence for the Theory of Evolution by Natural Selection

Rapid changes in populations under strong selection

E.g., pesticide resistance


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Human

Cat

Bat

Whale

Evidence for the Theory of Evolution by Natural Selection

Homologous traits (a.k.a. characters, attributes) = traits in different species that arose from the same ancestral trait (may or may not have similar function)

See

Fig.

22.14


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Evidence for the Theory of Evolution by Natural Selection

Even when homologies are not obvious in adults, they may be quite apparent in embryonic stages

Lemur Pig Human

Which one is the human?


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Evidence for the Theory of Evolution by Natural Selection

Analogous traits = traits in different species that have similar function, but arose from different ancestral traits


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To distinguish homologous vs. analogous traits, the relatedness of the organisms

doesn’t matter as much as the evolutionary history of the traits themselves


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Evidence for the Theory of Evolution by Natural Selection

Analogous traits = traits in different species that have similar function, but arose from different ancestral traits


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Evidence for the Theory of Evolution by Natural Selection

Vestigial organs = remnants of organs that had important functions in ancestors

These examples happen to be homologous leg and foot bones


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Evidence for the Theory of Evolution by Natural Selection

Vestigial organs = remnants of organs that had important functions in ancestors


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Evidence for the Theory of Evolution by Natural Selection

Biochemical homologies

Common use of DNA, RNA, amino acids, ribosomes, genetic code, ATP, electron carriers, electron transport system, etc.


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