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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
Proportion of students
In BIOL 1202,
good
attendance
First
Exam Score
versus Attendancepays off!
16
Attended all
Missed 66% or More
14
12
10
8
6
4
2
0
20-29
30-39
40-49
50-59
60-69
70-79
Final exam score
80-89
90-99
Chapter 22
Descent with
Modification:
A Darwinian
View of Life
Why are there so
many species?
The Theory of Evolution
by Natural Selection
Charles Darwin
Hypothesis vs. Theory
Hypothesis
Tentative explanation of
observations
Educated guess
Theory
General explanation of important
natural phenomena, developed through
extensive & reproducible observations
& experiments
Western Historical Context
Aristotle (384-322 B.C.) – Greek philosopher
Species are permanent, perfect, immutable
Dominant
world view
for > 2000 yr
See timeline Fig. 22.2
Western Historical Context
A.D. – Natural Theology (Creationism)
Species are permanent, perfect, immutable
See timeline Fig. 22.2
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
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
See Fig. 25.8
“King Philip Came
Over For Gumbo
Sunday”
Western Historical Context
Georges Cuvier (1769-1832)
French anatomist who largely developed
paleontology, the study of fossils
See timeline Fig. 22.2
Western Historical Context
Georges Cuvier (1769-1832)
Deeper strata contain older taxa
See timeline Fig. 22.2
Western Historical Context
Georges Cuvier (1769-1832)
Preferred hypothesis for profound geologic
change = catastrophism
See timeline Fig. 22.2
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
Western Historical Context
Charles Lyell (1797-1875)
Scottish geologist who incorporated Hutton’s
gradualism into the theory of
uniformitarianism
See timeline Fig. 22.2
Western Historical Context
Charles Lyell (1797-1875)
Uniformitarianism – geological processes &
rates today are those that also operated in
antiquity
See timeline Fig. 22.2
Western Historical Context
Charles Lyell (1797-1875)
Uniformitarianism – suggested that the Earth
is > 6000 yr old
See timeline Fig. 22.2
Western Historical Context
Jean Baptiste Lamarck (1744-1829)
Invertebrate Curator of
the 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
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
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
Western Historical Context
Within this context, Charles Darwin (18091882) served as Ship’s Naturalist on the HMS
Beagle’s circumnavigation of the globe
(1831-1836)
England
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
PACIFIC
OCEAN
Galápagos
Islands
HMS Beagle in port
SOUTH
AMERICA
AUSTRALIA
Andes
Darwin in 1840,
after his return
AFRICA
Cape of
Good Hope
Cape Horn
Tierra del Fuego
Tasmania
New
Zealand
Galapagos Islands, Ecuador
Galapagos Islands, Ecuador
Galapagos Islands, Ecuador
Galapagos Islands, Ecuador
Darwin was a good observer of both wild and
domesticated organisms (e.g., birds)
Darwin was a good observer of both wild and
domesticated organisms (e.g., birds)
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
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
Western Historical Context
Lyell presented the independently
derived hypothesis to the
Linnaean Society of London
on July 1, 1858
Western Historical Context
Charles Darwin (1809-1882)
The Origin of Species
(1859)
The Origin of Species
Final 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.”
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
Darwinian Theory of Evolution
Organisms have enormous potential for population
increase, but the potential is rarely reached
Generalized sigmoidal population growth curve
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 variability
results from heritable
differences
Adaptive evolution: A change in the phenotypic constitution
of a population owing to selection on heritable variation
among phenotypes
Lamarckism
Use
Inheritance of
acquired
characteristics
Darwinism
Natural
selection
Generation 1
Genetic
inheritance from
selected population
Generation 2
Evidence for the Theory of Evolution by Natural Selection
Darwin used artificial selection to illustrate the
modifying potential of selection
Evidence for the Theory of Evolution by Natural Selection
Darwin used artificial selection to illustrate the
modifying potential of selection
Evidence for the Theory of Evolution by Natural Selection
Darwin used artificial selection to illustrate the
modifying potential of selection
Evidence for the Theory of Evolution by Natural Selection
Rapid changes in populations under strong selection
E.g., pesticide
resistance
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
Human
Cat
Whale
Bat
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?
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
To distinguish homologous vs. analogous traits,
the relatedness of the organisms
doesn’t matter as much as the
evolutionary history of the
traits themselves
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
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
Evidence for the Theory of Evolution by Natural Selection
Vestigial organs = remnants of organs that had important
functions in ancestors
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.