Download Ch 9 evolution

Evolution:
Change in population characteristics over
generations
OUTLINE
Evolution and common descent
History of evolutionary thought
Evidence for evolution
Evaluating models
Evolutionary novelty
Goals: Be able to…
Central tenets of evolution
Explain the central tenets of evolution.
Explain how natural selection leads to evolution.
Describe how Darwin came up with the theory of
common descent.
1. Populations have changed over time into the
different species we see today
2. Theory of Common Descent: These populations
changed from a common ancestor
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Natural selection is a mechanism of evolution
Mixed lice
Resistant lice
survive
Resistant
lice
Apply
permethrin
Microevolution: Change over short periods
Fig 9.2
Fig 9.1
OUTLINE
Evolution and common descent
Speciation:
formation of new
species
History of evolutionary thought
Evidence for evolution
Evaluating models
Natural selection
Evolutionary novelty
Fig 9.2
Historical ideas about evolution:
Separate (“special”) creation:
Species are fixed on a
scale of complexity with
humans on top.
The world is perfect.
-- Plato, Aristotle …
Fig 9.7
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Theory of Common Descent
Lamarck:
1. Views of Lamarck
(evolutionist)
Organisms change
over generations
2. Views of Lyell (geologist)
3. Fossil evidence
4. Travels to Galapagos
Fossils of dinosaurs: some species don’t make it
Lyell
Due to the Biblical flood?
Result: The world is not
perfect
Or, due to gradual changes
over very long time periods?
Result: Earth is much > 10,000 yo
5 year expedition around the world
Galapagos giant tortoises
Fig 9.4
Different kinds of giant tortoises on different
islands
Result: Giant tortoises must be related, but
diverged over time
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Darwin published “On the Origin of Species by
Means of Natural Selection” in 1859
Giant
Alfred Russell Wallace
Darwin
Fig 9.2
True/False: Fossils of species that don’t exist
today, in combination with a lack of fossils of
modern species, support the idea that
organisms have NOT evolved over time.
1. True
2. False
OUTLINE
Evolution and common descent
History of evolutionary thought
Evidence for evolution
Evaluating models
Evolutionary novelty
Goals: Be able to…
Describe how classification, homology,
biogeography, and fossils all provide evidence
for the theory of common descent.
Differentiate between analogy and homology.
Apply your knowledge of radiometric dating to
problems.
Do you agree or disagree with the statement:
“Human beings, as we know them, developed
from earlier species of animals.”
1. Agree
2. Disagree
3. Don’t know
Discuss evidence refuting various alternative
hypotheses of evolution.
Describe 3 ways in which evolutionary novelty
can be generated by small changes.
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Agree
Disagree
“Human beings, as we
know them, developed
from earlier species of
animals.”
Hypothesis 1: Static model
Fig 9.7
Hypothesis 2: Transformation
Hypothesis 3: Separate types
Independent
origins
Fig 9.7
Fig 9.7
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Hypothesis 4: Common descent
Scientists investigate evolution, because
1. It is the only acceptable scientific explanation
for the observed patterns of change in
organisms over time.
2. They are not spiritual or religious people.
3. They want to disprove the existence of (a)
Creator(s).
4. All of the above.
Common origin
of life
Fig 9.7
Classification
suggests
relatedness
Evidence for Evolution
1. Biological classification
2. Homology of features
Why are we able to put organisms into groups?
3. Biogeography
4. Fossils!
Fig 9.9
Evidence for Evolution
1. Biological classification
2. Homology of features
3. Biogeography
Ancestry
represented
using trees
4. Fossils!
More closely
related = more recent
common ancestor
Fig 9.11
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Homology: Similarity of features due to common
ancestry
Homology
Vestigial structures: evolutionary baggage
Fig 9.12
Vestigial structures
Fig 9.13
Similar genetic sequences
Fig 9.17
True/False: A fish fin and a whale flipper are
homologous structures.
1. True
2. False
Evidence for Evolution
1. Biological classification
2. Homology of features
3. Biogeography: Geographic distributions
4. Fossils!
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Marsupials: Young
develop in pouches
Placentals
Marsupials
Analogy: similarity due to common function
Porpoise:
mammal
Evidence for Evolution
1. Biological classification
2. Homology of features
3. Biogeography
4. Fossils!
Icthyosaur:
reptile
Convergent evolution: similar features arise due
to common environmental pressure, not ancestry.
Transitions in the fossil record
Transitions in the fossil record
Archaeopteryx: transitional bird-lizard
Fig 9.28
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Fossilization: minerals replace organic matter
Age of the Earth
Radioactive elements “decay” at a
predictable rate.
Decay causes parent elements to
turn into daughter elements
Uranium Æ Lead
How do we know how old fossils are?
Half-life is the time it takes for ½ of
the parts to decay
Fig 9.21
Age of the Earth
Age of the Earth
100%
left
50%
left
25% 12.5%
left
left
1 half-life = 1
million yr
200 years ago
150 years ago
100 years ago
50 years ago
19% left = 2.5
half-lives
What is the half-life of this element?
Fig 9.24
Age of the Earth
Materials
dated
Shells,
Limestone,
organics
Method
Half-lives
Carbon/
Nitrogen
5,730 yrs
Potassium/
Argon
1.3 billion yrs
Volcanic rock
Rubidium/
Strontium
47 billion yrs
Micas
Uranium/Lead
4.5 billion yrs
Zircon
If an element has a half-life of 20 million years,
and there is 25% of it remaining in a rock, how
old is the rock?
1.
2.
3.
4.
5 million years
10 million years
20 million years
40 million years
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Group Problem: M&Mite decay
M&Mite spontaneously decays into the daughter
product “beanus” over time
OUTLINE
Evolution and common descent
1. Using your samples (baggies), graph # of
M&Mite molecules vs. Number of half-lives.
History of evolutionary thought
Evidence for evolution
Evaluating models
2. If your oldest sample is 1000 years old, what
is the half-life of M&Mite?
Evolutionary novelty
Hypothesis 1: Static model
Hypothesis 2: Transformation
What evidence refutes this theory?
What evidence refutes this theory?
Fig 9.7
Fig 9.7
Hypothesis 3: Separate types
Hypothesis 4: Common descent
What evidence refutes this theory?
Independent
origins
Fig 9.7
Common origin
of life
Fig 9.7
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We can reject the static hypothesis, because
1. We usually do not find fossils record that are
exactly the same as living organisms.
2. Example
Fossil evidence
indicates that many organisms
short
answer:
have gone
extinct.
3. List
Many
diverse
a basic
structure
2 pieces
of features
evidenceshare
that refute
the
static
(bat wing &For
whale
flipper
hypothesis.
each
piece,bones).
state which aspect
4. ofWe
findhypothesis
fossils transitional
between
thecan
status
is refuted.
different organisms that are currently alive.
5. All of the above.
OUTLINE
Evolution and common descent
History of evolutionary thought
Evidence for evolution
Evaluating models
Evolutionary novelty
Exaptations: Features originally performed a
different function than they currently do.
Generation of evolutionary novelty
• Exaptation
• Developmental mutations
• Intermediate forms
Mutations in developmental genes…
Intermediate forms
Pigment cells
Pinhole eye
Complex camera
eye
Eyecup
Primitive
lens
Amphistoma larva
Have widespread effects
Axolotl adult
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True/False: Both bird feathers and the human
eye are irreducibly complex
1. True
2. False
Group Problem: Birds on Islands
A = Red feathers, blue
beaks
A
B
C
C = Yellow feathers, blue
beaks
Example short answer:
In 1-2 sentences, describe how feathers on
birds may have evolved.
B = Red feathers, black
beaks
1. Draw 2 possible phylogenetic trees for these 3
species.
2. What specific evidence would help you choose
between these 2 hypotheses?
Goals: Be able to…
Primates
Describe features that 1) we share with other
primates, 2) differentiate apes from other
primates, and 3) differentiate us from apes.
• Grasping hands
Describe the environment in which primate
features evolved.
• Large brains
Explain why Lucy was such an important find.
• Forward-facing eyes
Why? Adaptation for forest life
Discuss hypotheses about the origins of
bipedalism and big brains.
Tell me when modern humans arose, and about
their Homo ancestors.
Prosimians: Lemurs and tarsiers
Monkeys and apes
Earliest diverging
Opposable
thumb!
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Apes
• No tail
• Long forelimbs
• Larger brains
Orangutans
Gorillas
Fig 9.11
Chimpanzees
Bonobos
What human features were probably
adaptations for forest life?
1. Fingernails
Example
short answer:
2.
Forward-facing
eyes
List 2 human features
that were originally
3. Opposable
adaptations
for thumbs
forest life.
4. Lack of hair
-OR5. 2 and 3
Give
2 ways
which apes are distinct from
6. All
of thein
above
other primates.
What does it mean to be human?
1) Large brain
2) Bipedalism
3) Short jaw
4) Reduced sexual differences 5) Monogamy
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Hominins: Most closely related to us.
Comparing humans
vs. chimps
Diverged from chimpanzee
line: 5-7 mya?
Fig 9.22
Fig 9.25
What features separate humans from other apes?
Enlarging brain
Example
short answer:
1. Forward-facing
eyes
2. Opposable
thumbs
What
are the most
critical 2 ways in which
human
anatomy
3. Long
arms differs from other apes?
4. Largest brain
Fig 9.27
Dry savanna provides more complexity?
Looking for 2 major features:
• Bipedal posture
• Enlarged brain
How did they evolve?
Early ideas:
+
Bipedal
posture
Brain size
+
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Along came Lucy…
Problem: Bipedal with small brain
Fig 9.23
Australopithecus afarensis
Fig 9.23
~ 3.5 mya: Australopithecus afarensis
Homo sapiens
Why bipedalism?
Early theories:
+
Environmental change Æ dry savannas
Bipedal
posture
Brain size
Why might bipedalism be favorable in a
savanna (as opposed to forest) environment?
+
Bipedal posture is the key!!!
Why bipedalism?
Environmental change Æ dry savannas
Not using hands for tree
climbing?
Bipedalism paved the way for large brain?
Babies born smaller due to pelvis…
Longer care of infants Æ more culture?
Easier to see far away?
Easier to carry things?
Hands free to create tools…?
Prevent overheating?
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True/False: Looking at human evolution, we
can see that bipedalism developed before large
brain size.
Genus: Homo
1. True
2. False
Example short answer:
What did the fossil Lucy demonstrate about the
order of evolution of bipedalism and big brains?
Fig 9.25
Homo habilis: “handy-man”
Homo erectus
First tool-maker
Specialized tools
Brain size: 47%
of ours
Brain size: 71%
Neanderthals: 500,000 – 30,000 years ago?
Homo sapiens neanderthalensis
Homo erectus colonized Asia and Europe
Brain size:
12% larger
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Homo sapiens sapiens: 100,000 years ago.
Origins of agriculture begin 9500 BC
Cultural evolution…
Homo floresiensus: The Hobbit
Alive 13,000 years ago
Example short answer:
What scientific support is there that humans
share a common ancestor with chimpanzees?
What do you think about the statement:
“God created man pretty much in his present
form at one time within the last 10,000 years.”
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