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

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BIOL 1202, Section 1
Dr. Kyle Harms
Course website
http//www.biology.lsu.edu/webfac/kharms/BIOL1202F
all2007.htm
http//www.biology.lsu.edu/webfac/kharms/BIOL1202F
all2007.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?
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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

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

Species are permanent, perfect, immutable
Dominant world view for gt 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 genus
Canis 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 Huttons
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 gt
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 19th
centuries 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
Within this context, Charles Darwin (1809-1882)
served as Ships Naturalist on the HMS Beagles
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
Use
Inheritance of acquired characteristics
Darwinism
Genetic inheritance from selected population
Natural selection
Generation 1
Generation 2
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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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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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doesnt matter as much as the evolutionary
history of the traits themselves
To distinguish homologous vs. analogous traits,
the relatedness of the organisms
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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.