Download Descent with Modification PPT part 1

Chapter 22
Descent with Modification: A
Darwinian View of Life
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A new era of biology began on November 24, 1859,
the day Charles Darwin published On the Origin of
Species by Means of Natural Selection
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Darwin made two major points in his book:
– Many current species are descendants of
ancestral species
– Natural selection is a mechanism for this
evolutionary process
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 22-2
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
Mendel (inheritance)
Wallace (evolution, natural selection)
American Revolution
U.S. Civil War
French Revolution
1850
1900
1750
1800
1795 Hutton proposes his theory of gradualism.
1798 Malthus publishes “Essay on the Principle of Population.”
1809 Lamarck publishes his theory of evolution.
1830 Lyell publishes Principles of Geology.
1831–1936 Darwin travels around the world on HMS Beagle.
1837 Darwin begins his notebooks on the origin of species.
1844 Darwin writes his essay on the origin of species.
1858 Wallace sends his theory to Darwin.
1859 The Origin of Species is published.
1865 Mendel publishes inheritance papers.
Theories of Gradualism
• Gradualism is the idea that profound change can
take place through the cumulative effect of slow
but continuous processes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Geologists Hutton and Lyell perceived that
changes in Earth’s surface can result from slow
continuous actions still operating today
• This view strongly influenced Darwin’s thinking
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Lamarck’s Theory of Evolution
• Lamarck hypothesized that species evolve
through use and disuse and the inheritance of
acquired traits
• The mechanisms he proposed are unsupported by
evidence
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 22-5
England
EUROPE
NORTH
AMERICA
PACIFIC
OCEAN
ATLANTIC
OCEAN
AFRICA
Galápagos
Islands
HMS Beagle in port
Equator
SOUTH
AMERICA
Darwin in 1840,
after his return
AUSTRALIA
Cape of
Good Hope
Tasmania
Cape Horn
Tierra del Fuego
New
Zealand
Galapagos Islands
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 22-6
Cactus eater. The long,
sharp beak of the
cactus ground finch
(Geospiza scandens)
helps it tear and eat
cactus flowers and
pulp.
Seed eater. The large
ground finch (Geospiza
magnirostris) has a large
beak adapted for cracking
seeds that fall from plants
to the ground.
Insect eater. The green warbler finch
(Certhidea olivacea) used its narrow,
pointed beak to grasp insects.
Descent with Modification
• The phrase descent with modification
summarized Darwin’s perception of the unity of life
Sirenia
Hyracoidea (Manatees
(Hyraxes) and relatives)
0
10,000
2
5.5
24
34
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Elephas Loxodonta Loxodonta
cyclotis
maximus africana
(Africa)
(Africa)
(Asia)
Natural Selection and Adaptation
• Evolutionary biologist Ernst Mayr has dissected
the logic of Darwin’s theory into three inferences
based on five observations
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Natural Selection and Adaptation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Observation #1: For any species, population
sizes would increase exponentially if all individuals
that are born reproduced successfully
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Observation #2: Populations tend to be stable in
size, except for seasonal fluctuations
• Observation #3: Resources are limited
• Inference #1: Production of more individuals than
the environment can support leads to a struggle
for existence among individuals of a population,
with only a fraction of their offspring surviving
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Observation #4: Members of a population vary
extensively in their characteristics; no two
individuals are exactly alike
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Observation #5: Much of this variation is heritable
• Inference #2: Survival depends in part on
inherited traits; individuals whose inherited traits
give them a high probability of surviving and
reproducing are likely to leave more offspring than
other individuals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Inference #3: This unequal ability of individuals to
survive and reproduce will lead to a gradual
change in a population, with favorable
characteristics accumulating over generations
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Natural Selection
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings