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Chapter 10
Principles of Evolution
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Overview: Endless Forms Most Beautiful
• A new era of biology began in 1859
when Charles Darwin published The
Origin of Species
• The Origin of Species focused
biologists’ attention on the great
diversity of organisms
• Darwin noted that current species are
descendants of ancestral species
• Evolution can be defined by Darwin’s
phrase descent with modification
• Evolution can be viewed as both a
pattern and a process
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Darwin’s Two Major Points from Origin of Species
1. Presented evidence that many species of organisms
presently inhabiting the Earth are descendents of
ancestral species (common descent)
2. Proposed a mechanism for the evolutionary process
(natural selection)
 a population’s allele frequency can change over
generations if individuals that possess certain heritable
traits leave more offspring than others
 results in evolutionary adaptation – accumulation of
inherited characteristics that enhance organisms’
ability to survive and reproduce in specific
environments
 evolution – change over time in genetic composition
of a population and could eventually lead to new
species
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-1
The Historical Context of Darwin’s Life and Ideas
Lamarck’s Hypothesis of Evolution
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Fig. 22-4
Fig. 22-5
GREAT
BRITAIN
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
The
Galápagos
Islands
AFRICA
Pinta
Genovesa
Equator
Marchena
Santiago
Fernandina
Isabela
Daphne
Islands
Pinzón
Santa
Santa
Cruz
Fe
Florenza
SOUTH
AMERICA
AUSTRALIA
PACIFIC
OCEAN
San
Cristobal
Cape of
Good Hope
Tasmania
Española
Cape Horn
Tierra del Fuego
New
Zealand
Darwin’s Focus on Adaptation
• In reassessing his observations, Darwin
perceived adaptation to the environment and the
origin of new species as closely related
processes:
– An adaptation is a genetic variation that is favored
by selection and is manifested as a trait that
provides an advantage to an organism in a
particular environment.
– Any heritable trait that increases an organism’s
reproductive capability as compared to those
without the trait.
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Galapagos Finches
The Origin of Species
• In 1844, Darwin wrote an essay on the origin of species
and natural selection but did not introduce his theory
publicly, anticipating an uproar
• In June 1858, Darwin received a manuscript from Alfred
Russell Wallace, who had developed a theory of natural
selection similar to Darwin’s
• Darwin quickly finished The Origin of Species and
published it the next year
• In his manuscript, Darwin developed two main ideas:
–
Descent with modification explains life’s unity and diversity
–
Natural selection is a cause of adaptive evolution
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-9
Terminal
bud
Lateral
buds
Cabbage
Brussels sprouts
Flower
clusters
Leaves
Kale
Cauliflower
Stem
Wild mustard
Flowers
and stems
Broccoli
Kohlrabi
Fig. 22-10
Fig. 22-11
Spore
cloud
Darwin’s Big Ideas – The Inferences
• Inference #1: Individuals whose inherited traits
give them a higher probability of surviving and
reproducing in a given environment tend to
leave more offspring than other individuals
• Inference #2: This unequal ability of
individuals to survive and reproduce will lead to
the accumulation of favorable traits in the
population over generations
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-UN1
Observations
Individuals in a population
vary in their heritable
characteristics.
Organisms produce more
offspring than the
environment can support.
Inferences
Individuals that are well suited
to their environment tend to leave
more offspring than other individuals
and
Over time, favorable traits
accumulate in the population.
Competition for Resources
• Darwin was influenced by Thomas Malthus
who noted the potential for human population
to increase faster than food supplies and other
resources
• If some heritable traits are advantageous,
these will accumulate in the population, and
this will increase the frequency of individuals
with adaptations
• This process explains the match between
organisms and their environment
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Natural Selection: A Summary
• Individuals with certain heritable characteristics
survive and reproduce at a higher rate than
other individuals
• Natural selection increases the adaptation of
organisms to their environment over time
• If an environment changes over time, natural
selection may result in adaptation to these new
conditions and may give rise to new species
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Natural Selection: A Summary
FITNESS is measured as
REPRODUCTIVE success.
Natural selection is differential
success in reproduction - it
results from the interaction
between individuals that vary in
heritable traits and their
environment.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-12
(a) A flower mantid
in Malaysia
(b) A stick mantid
in Africa
Natural Selection: A Summary
1. Overpopulation - more organisms are born than can
survive
2. Variation within a population - there will be many
variation for different traits among individuals
3. Competition within the population - individuals will
compete for survival: food, mates, shelter, etc.
4. Survival of the Fittest - those with traits best suited to
the environment will be more likely to survive
5. Reproduction - individuals that survive will pass their
traits on to the next generation
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Key Points to Remember
1. Population - group of interbreeding individuals
belonging to a particular species and sharing a
common geographic area
2. A population is the smallest unit that can
evolve
3. Natural selection occurs because of interaction
between organisms and their environments
4. Natural selection works to increase or decrease
the occurrence of heritable traits
5. Individuals are selected, but populations evolve
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Key Points to Remember
1. Theory - an accepted hypothesis that has been tested
over and over again without yet being disproved
2. Definition - Evolution is the change in the overall genetic
makeup (allele frequency) of a population over time
3. Three Basic Components
a. Individuals cannot evolve. Populations evolve.
b. Natural selection is the mechanism of evolution.
c. Evolution occurs by chance (NOT GOAL ORIENTED).
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Evolution and the Environment
• Natural selection does not create new traits,
but edits or selects for traits already present in
the population
• The local environment determines which traits
will be selected for or selected against in any
specific population
• Because environments change, they act as
selective mechanisms on populations
– Example: peppered moth
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Evolution and the Environment
Peppered Moth
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Evidence for Evolution
•
Evolution is supported by an overwhelming
amount of scientific evidence
•
New discoveries continue to fill the gaps
identified by Darwin in The Origin of Species
•
Three examples provide direct evidence for
natural selection:
1. the evolution of insecticide resistance;
2. and the evolution of drug-resistant HIV
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Evolution of Insecticide Resistance
1. By spraying crops with poisons
to kill insects, humans have
unwittingly favored the
reproductive success of insects
with inherent resistance to
poisons.
2. Resistant individuals survive
and reproduce, passing the
gene for resistance to offspring.
3. Additional applications of the
same insecticide will be less
effective, and the frequency of
resistant insects in the
population will grow.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Evolution of Drug-Resistant HIV
• The use of drugs to combat HIV selects for
viruses resistant to these drugs
• HIV uses the enzyme reverse transcriptase to
make a DNA version of its own RNA genome
• The drug 3TC is designed to interfere and
cause errors in the manufacture of DNA from
the virus
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-14
100
Patient
No. 1
Patient No. 2
75
50
Patient No. 3
25
0
0
2
4
6
Weeks
8
10
12
Evidence for Evolution
• Evidence that the diversity of life is a product of
evolution pervades every research field of biology.
– Fossil Record Evidence
– Succession of Fossil Forms
– Comparative Anatomy
– Anatomical Homologies
– Embryological Homologies
– Molecular Homologies
– Biogeography
–
Geographic Distribution of Species
–
Continental Drift
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Evidence for Evolution
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
How Rocks and Fossils Are Dated
• Sedimentary strata reveal the relative ages of
fossils:
– In relative dating, the order of rock strata is used to
determine the relative age of fossils. Older specimens
are found in deeper layers of strata.
• The absolute ages of fossils can be determined by
radiometric dating
– Radiometiric dating uses the decay of radioactive
isotopes to determine the age of the rocks or fossils.
– It is based on the rate of decay, or half-life of the
isotope (the time required for half the parent isotope to
decay).
Fig. 22-17
Homology
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Homologous structures are those found in different species that are
similar and result from common ancestry.
Bat
Fig. 22-18
Comparative Embryology
Pharyngeal
pouches
Post-anal
tail
Chick embryo (LM)
Human embryo
Vestigial Structures
The skeletons of
some snakes retain
vestiges of the
pelvis and leg bones
of walking
ancestors.
We would not
expect to see these
structures if snakes
had an origin
separate from other
vertebrate animals.
Molecular Homologies
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Convergent Evolution
• Although organisms that are closely related
share characteristics because of common
descent, distantly related organisms can
resemble one another for a different reason:
– Convergent evolution is the evolution of similar, or
analogous, features in distantly related groups.
– Analogous traits arise when groups independently
adapt to similar environments in similar ways.
– Convergent evolution does not provide information
about ancestry!
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Homologous v. Analogous Structures
• Homologous structures
are similar structures
occurring in different
species that are believed to
be derived from a common
ancestor.
• Analogous structures are
similar structures occurring
in different species that are
believed to be the result of
convergent evolution
(similar environmental
pressures).
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-20
Sugar
glider
NORTH
AMERICA
AUSTRALIA
Flying
squirrel
Biogeography
• Darwin’s observations of biogeography, the geographic
distribution of species, formed an important part of his
theory of evolution
– Islands have many endemic species that are often
closely related to species on the nearest mainland or
island
– Earth’s continents were formerly united in a single
large continent called Pangaea, but have since
separated by continental drift
– An understanding of continent movement and modern
distribution of species allows us to predict when and
where different groups evolved
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The Geographic Distribution of Species
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Continental Drift
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Endemic Species
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Populations of Organisms Continue to Evolve
•
Scientific evidence supports the idea that evolution has
occurred in all species.
•
Scientific evidence supports the idea that evolution
continues to occur:
–
Chemical Resistance: mutations for resistance to
antibiotics, pesticides, herbicides or chemotherapy
drugs occur in the absence of the chemical.
–
Emergent Diseases: mutations that allow diseases to
expand their host range.
–
Observed Directional Phenotypic Changes: Grant’s
observations of Darwin’s finches in the Galapagos.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Summary of Darwin’s Theory
http://bcs.whfreeman.com/thelifewire/content/chp23/2302003.html
1.
Individual organisms in nature differ from one another and some of
this variation is inherited
2.
Organisms in nature produce more offspring than can survive – and
many that survive do not reproduce
3.
Members of each species must compete for resources
4.
Individuals best suited to their environment survive and reproduce
most successfully – they pass their traits onto their offspring
5.
Species change over time – this is caused by natural selection – new
species arise and other species disappear
6.
Species alive today have descended with modifications from species
that lived in the past
7.
All organisms on Earth are united into a single tree of life by common
descent
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings