Transcript Chapters 2 and 3

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Fitness
◦ Survival and reproduction
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Adaptation
◦ A relative increase in fitness
What it is
and
What is NOT
A.
B.
True
False
A.
B.
True
False
A.
B.
True
False
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Increase in complexity, organization or
specialization may occur
No specific end goal in mind, however
There is no trend toward more advanced
forms, could just as easily go in reverse
(oscillating selection).
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The following claim is often made:
“Of course individuals with favorable
variations are the ones that survive and
reproduce because the theory defines
favorable as the ability to survive and
reproduce.”
What is wrong with this argument?
A.
B.
True
False
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Where does variation come from?
How are traits inherited from parents?
Mayr article discussion
•Studied biodiversity and origin of new taxa
•Macroevlolution
•Properties in individuals are objects of
selection
•Speciation is a gradual accumulation of
changes
A.
B.
Geneticists
Naturalists
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Genetics
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Based on small changes within populations
Microevolution
Gene is the object of selection
Mutations lead to saltational speciation
Naturalists
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Studied biodiversity and origin of new taxa
Macroevlolution
Properties in individuals are objects of selection
Speciation is a gradual accumulation of changes
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First what was well accepted?
◦ Change in organisms occurs over time
◦ The branching theory implying common descent
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What had difficulty being accepted?
◦ That evolution was a gradual process
◦ That species multiplied (increase in diversity)
◦ That natural selection was the means
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Scientists worked in isolation in different
countries. Beliefs in each country were
dictated by the most powerful scientists.
Scientists in different branches of biology had
different prevailing ideas
Each group thought that the other group had
no flexibility in their beliefs.
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Geneticists
◦ Worked in labs and studied the processes in single
populations
◦ Only examined changes within a populationmicroevolution
◦ Believed each mutation led to a new species
◦ Believed speciation was saltational
◦ Gene is the object of selection
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Developed mutation theory
Any new variation caused by mutation was
actually a new species
Emphasized random genetic variation (no
guidance by selection)
Speciation abrupt and spontaneous
◦ Studied biodiversity and the origin of new species
and higher taxa - macroevolution
◦ Changes occur gradually as Darwin said
◦ Individual is object of selection not the gene
◦ New species are formed by geographic isolation
A.
B.
Naturalist
Geneticist
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Geneticists also called mutationists
◦ William Bateson and Hugo DeVries
◦ Other geneticists who also believed evolution was
gradual were not as well known to naturalists.
 Edward East and Sergei Chetverikov.
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Moritz Wagner
Karl Jordan
Edward Poulton
Sergei Chetverikov
Erwin Stresemann
Ernst Mayr and
Julian Huxley
A.
B.
C.
D.
E.
Thomas Hunt Morgan
Theodosius Dobzhansky
Ledyard Stebbins
Ernst Mayr
R. A. Fisher
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Thomas Hunt Morgan – his research was a key
factor in the synthesis
◦ He showed (working with Drosophila) that
 mutations occurred in every generation and
 that the resulting populations were reproductively
isolated and were not new species.
 Mutations simply increased the variability of a
population.
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Theodosius Dobzhansky – was a naturalist in
Russia, came to US and worked in Morgan’s lab
◦ He saw how they were complimentary to each other.
 Mutations provide the new alleles that increases variation
in populations.
◦ Geographically separated populations can then
respond to different environments
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gradually, become separate species.
Over more time new higher taxa can emerge.
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Selection acts on individuals but has its
effects in populations.
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Population genetics and microevolution.
◦ R.A. Fisher – mathematician showed variability in
populations could be explained using Mendel’s laws
 Genetical Theory of Natural Selection
 Believed selection was favored in large populations because
variability remains high due to mutation and genetic
recombination
 Selection acts uniformly and slowly
◦ J.B.S. Haldane
 Same basic understanding as Fisher but he emphasized the
use of practical examples for his models ( e.g industrial
melanism and moths)
Sewall Wright
 Mathematical techniques to show that evolution could
proceed in isolated groups
 Developed the ideas of genetic drift. (based on the work of
William Castle)
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John Maynard Smith
◦ Extended the Darwinian theory to explanation of animal
behavior
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Ledyard Stebbins –
◦ did for plant evolution what Dobzhansky with his fruit
flies had done for animal evolution
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George Gaylord Simpson
◦ Reinterpreted the fossil record
◦ Major responsibility for paleontologists embracing
Darwin's ideas.
Showing the same trend only in opposite
direction
1. Direct Observation of
Change Through Time
Anatomical
2. Evidence
from vestigial
structures
Embryonic or developmental
Embryonic Vestigial
structures
Vestigial Genes
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Gene for CMAH enzyme (processes a sugar found
on surface of chimp cells)
◦ DNA sequence for the gene is found in both humans and
chimps
◦ However the gene is disabled in humans by a deletion
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Causes a different biochemical signature on the
surfaces of human and chimp cells.
Gene in humans is leftover from a common
ancestor that humans share with chimps
Evidence against a separate origin for humans.
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A test for interpretation of vestigial molecular
traits
Can anyone relate this story on page 43?
Heavy plating in marine
Light plating in fresh water
Cresko and colleagues identified that most of
the control for this trait was due to 2
Mendelian-inherited genes
Predicted rapid evolution from marine to
fresh water form
This was later demonstrated by the
experiments of Michael Bell
Extinct Species
1. Extinct
species
The fossil
record
provides
many
examples of
species that
once lived on
the earth but
are now
extinct.
Irish Elk
Law of Succession
2. The Law of Succession
Wombat
Armadillo
Glyptodont
Connection made by
Charles Darwin
Diptotodon
Connection made by
Richard Owen
Transitional sequences
3. Transitional Fossils
Discovered about
1860
Discovered about
1997
More feathered dinosaurs discovered in the late 1990s
Another of Darwin’s premises
Ring Species
1. Ring Species
Pg. 53
Siberian Greenish Warbler
Homology
2. Homology from 3 areas
Structural Homology
Developmental Homology
1.
2.
3.
Genetic Code is identical in essentially all
species
Shared flaws in genetic makeup
Psuedogenes (CMAH in humans)
Shared genetic flaws found in Chimps and Bonobos but not ion Gorillas and
Orangutans also
Flaw
leads to mistakes
Page 57
Pseudogenes (Pg 58) shared among species
Age of pseudogenes is determined by the number
of mutations they contain.
Relationships among species
Relationships
among
species
Discussed on Page 60
1.
2.
Principle of Uniformitarianism
Geologic time scale\
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2.
3.
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5.
3.
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Younger rocks on top of older ones
Originally in horizontal position
Rocks that intrude into seams are younger
Boulders, cobbles are older than the host rock
Earlier fossil life forms are simpler, more recent
are most similar to extant forms.
Radiometric dating
Dating the earth’s actual age from its molten
state.