Chapter 22 Part 3 Descent with Modification

Report
Concept 22.3: 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
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Direct Observations of
Evolutionary Change
• Two examples provide evidence for
natural selection: the effect of
differential predation on guppy
populations and the evolution of
drug-resistant HIV
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Direct Observations
•
•
•
•
Color patterns in guppies
Drug resistant HIV
Beak size in Birds
Others
Predation and Coloration in Guppies
: Scientific Inquiry
• John Endler has studied the effects of
predators on wild guppy populations
• Brightly colored males are more
attractive to females
• However, brightly colored males are more
vulnerable to predation
• Guppy populations in pools with fewer
predators had more brightly colored
males
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Color Pattern in Guppies
• Field Experiment (see text for full
details)
• Changed the selection pressure on
male guppies
• Result – color pattern change in 15
generations (22 months).
• Endler transferred brightly colored guppies (with
few predators) to a pool with many predators
• As predicted, over time the population became less
brightly colored
• Endler also transferred drab colored guppies (with
many predators) to a pool with few predators
• As predicted, over time the population became
more brightly colored
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HIV Drug Resistance
• Drug resistance strains selected
for by treatments
• Result – resistant strains became
100% dominant in 4-5 weeks.
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
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
• Some individual HIV viruses have a variation that
allows them to produce DNA without errors
• These viruses have a greater reproductive success
and increase in number relative to the susceptible
viruses
• The population of HIV viruses has therefore
developed resistance to 3TC
• The ability of bacteria and viruses to evolve rapidly
poses a challenge to our society
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Beak Size
• Field Study – measured the beak size of
all birds in a population over several
years.
• Result – drought and food competition
changed beak size.
Fossils
• Relics or impressions of organisms from
the past.
• Problem:
– Show changes over time from simple to
complex.
– Many fossils don't have descendants.
Evolution Viewpoint
• Life has
changed over
time.
• Many species
failed to
survive and
became
extinct.
Comments
1. Fossilization is a rare event.
2. Only hard parts fossilize well.
3. Problem in finding fossils.
4. Interpretation.
5. Missing Links.
• 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
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The Fossil Record
• The fossil record provides evidence of the
extinction of species, the origin of new groups, and
changes within groups over time
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Fossil Record
• The fossil record provides evidence of the
extinction of species, the origin of new groups, and
changes within groups over time
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 22-15
0
2
4
4
6
4 Bristolia insolens
8
3 Bristolia bristolensis
10
12
3
14
2 Bristolia harringtoni
16
18 1 Bristolia mohavensis
3
2
1
Latham Shale dig site, San
Bernardino County, California
• The Darwinian view of life predicts that
evolutionary transitions should leave signs in the
fossil record
• Paleontologists have discovered fossils of many
such transitional forms
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Fig. 22-16
(a) Pakicetus (terrestrial)
(b) Rhodocetus (predominantly aquatic)
Pelvis and
hind limb
(c) Dorudon (fully aquatic)
Pelvis and
hind limb
(d) Balaena
(recent whale ancestor)
Homology
• Homology is similarity resulting from common
ancestry
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Homology
Homologous
Structures Common
"building plan”
with divergent
functions.
Mammal forelimbs
Fig. 22-17
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
Anatomical and Molecular Homologies
• Homologous structures are anatomical
resemblances that represent variations on a
structural theme present in a common ancestor
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Vestigial Organs
Whale Legs
Rudimentary
structures
of marginal,
if any, use.
Human Example
Human Example
Evolution Viewpoint
• Remodeling of ancestral structures
as their functions or adaptations
changed.
Homology in Embryos
• Closely related organisms go
through similar stages in their
embryonic development.
• Ex: Gill pouches in vertebrates
• Comparative embryology reveals anatomical
homologies not visible in adult organisms
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• Vestigial structures are remnants of features that
served important functions in the organism’s
ancestors
• Examples of homologies at the molecular level are
genes shared among organisms inherited from a
common ancestor
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Homologies and “Tree Thinking”
• The Darwinian concept of an evolutionary tree of
life can explain homologies
• Evolutionary trees are hypotheses about the
relationships among different groups
• Evolutionary trees can be made using different
types of data, for example, anatomical and DNA
sequence data
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Convergent Evolution
• 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
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Convergent Evolution
• Unrelated organisms show similar
adaptations.
• Cause – lived in a similar environment
with similar selection pressures.
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
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• 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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Evolution Viewpoint
• Biogeographical patterns reflect
descent from the ancestors that
colonized that area.
Molecular Biology
• Study of Evolution at the DNA or
protein levels.
• Related species have similar DNA
sequences.
Evolution Viewpoint
• Related species share a common
ancestrial DNA. The closer the
relationship, the more similar the DNA
sequences should be.
What Is Theoretical About Darwin’s
View of Life?
• In science, a theory accounts for many observations
and data and attempts to explain and integrate a
great variety of phenomena
• Darwin’s theory of evolution by natural selection
integrates diverse areas of biological study and
stimulates many new research questions
• Ongoing research adds to our understanding of
evolution
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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.
Fig. 22-UN2
Fig. 22-UN3
You should now be able to:
1. Describe the contributions to evolutionary theory
made by Linnaeus, Cuvier, Lyell, Lamarck, Malthus,
and Wallace
2. Describe Lamarck’s theories, and explain why they
have been rejected
3. Explain what Darwin meant by “descent with
modification”
4. List and explain Darwin’s four observations and
two inferences
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
5. Explain why an individual organism cannot evolve
6. Describe at least four lines of evidence for
evolution by natural selection
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Summary
• Darwin's ideas now a "Theory”.
• Predictions of a Theory are tested
by experiments and observations.
• Be familiar with the pre-Darwin
views of evolution.
Summary
• Know Darwin’s “observations” and
“inferences”.
• Be able to discuss the various
evidences of Darwinian evolution.

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