Download On the Origin of Species

Descent w/ Modification
Chapter 22
Lecture Objectives
1. Charlies Darwin – Before &
After
2. Descent w/ Modification &
Natural Selection
3. Evidence for Evolution
CHARLES DARWIN AND THE ORIGIN OF SPECIES
 Biology came of age on November 24, 1859. Charles Darwin published
On the Origin of Species by Means of Natural Selection, an assemblage of facts
about the natural world.
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Historical context of Darwin’s ideas
 Common beliefs
Who created living organisms?
Did they evolve?
What was the age of the earth?
Did the earth change?
1809
Lamarck publishes his
hypothesis of evolution.
1798
Malthus publishes
“Essay on the Principle
of Population.”
1795
Hutton proposes
his principle of
gradualism.
1812
Cuvier publishes his
extensive studies of
vertebrate fossils.
1830
Lyell publishes
Principles of Geology.
Sketch of a flying
frog by Wallace
1858
While studying species in the
Malay Archipelago, Wallace
(shown above in 1848) sends
Darwin his hypothesis of
natural selection.
1790
1870
1809
Charles Darwin
is born.
1831–1836
Darwin travels
around the world
on HMS Beagle.
Marine iguana
in the
Galápagos
Islands
Figure 22.2
1859
On the Origin of
Species is published.
1844
Darwin writes his
essay on descent
with modification.
Darwin in 1840,
after his return
from the
voyage
HMS Beagle in port
Great
Britain
NORTH
AMERICA
EUROPE
ATLANTIC
OCEAN
The
Galápagos
Islands
Genovesa
Marchena
Santiago
Fernandina
Isabela
0
20 40
AFRICA
PACIFIC
OCEAN
Pinta
SOUTH
AMERICA
Equator
Daphne
Islands
Pinzón
Santa Santa
Cruz
Fe
Florenza
Kilometers
Figure 22.5
San
Cristobal
Chile
PACIFIC
OCEAN
Equator
Brazil
Cape of
Good Hope
Argentina
Española
Cape Horn
Malay
Archipelago
PACIFIC
OCEAN
AUSTRALIA
Tasmania
New
Zealand
The Grand Canyon

(a) Charles Darwin and (b) Alfred Wallace wrote scientific papers on natural selection that were
presented together before the Linnean Society in 1858.
CHARLES DARWIN’S UNEXPECTED
PATTERNS
1. Was it possible for a species to diverge from
the original population?
2. Similarity between fossils of extinct & extant
species occurred at every location
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(a) Cactus-eater
Figure 22.6
(b) Insect-eater
(c) Seed-eater
CHARLES DARWIN’S UNEXPECTED
PATTERNS CON’T.
Glyptodont
Hairy Armadillo
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Darwin’s Two Main Points in The Origin of
Species
1. Descent with Modification  Organisms
inhabiting Earth today descended from ancestral
species.
- As organisms spread over various habitats,
they are modified or changed by
accumulating adaptations to diverse ways of
life
- AKA evolution: a change in the genetic
composition of a population over time.
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Darwin’s Two Main Points in The Origin of Species
con’t.
2. Natural Selection is the mechanism for descent with
modification
 Process in which organisms with certain inherited
characteristics are more likely to survive and reproduce
than are individuals with other characteristics.
 Populations change over generations.
 Natural selection thus leads to evolution.
 Darwinian Fitness: measure of viable offspring
compared to other members of that species
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EVIDENCE OF EVOLUTION
 Evolution leaves observable signs.
 We will examine five of the many lines of evidence in
support of evolution:
1. the fossil record,
2. biogeography,
3. comparative anatomy,
4. comparative embryology, and
5. molecular biology.
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Australia
Common
ringtail
possum
Koala
Common wombat
Red kangaroo
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Figure 22.15
Cat
Whale
Bat
Pharyngeal
arches
Post-anal
tail
Chick embryo (LM)
Figure 22.16
Human embryo
Primate
Percent of selected DNA
sequences that match a
chimpanzee’s DNA
92%
Chimpanzee
Human
Gorilla
Orangutan
Gibbon
Old World
monkey
96%
100%
Support for Natural Selection according to Darwin
1. All species tend to produce excessive offspring
2. Organisms vary  heritable.
Fig. 22.10
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Fig. 22.11
Natural Selection in Action Today
 Examples of natural selection include
 pesticide-resistant insects,
 antibiotic-resistant bacteria, and
 drug-resistant strains of HIV.
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Evolved Beliefs after On the Origin of
Species
 Organisms can change over time.
 Some organisms have gone extinct.
 Earth is ~ 4.5 billion years old
 The geology of the earth is not constant, but
always changing.
 Organisms descend from ancestral species.