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Fitness◦ Survival and reproduction
Adaptation◦ A relative increase in fitness
What it isand
What is NOT
A. TrueB. False
A. TrueB. False
A. TrueB. False
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).
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. TrueB. False
Where does variation come from? How are traits inherited from parents?
Mayr article discussion
A. GeneticistsB. Naturalists
•Studied biodiversity and origin of new taxa•Macroevlolution•Properties in individuals are objects of selection•Speciation is a gradual accumulation of changes
Genetics◦ Based on small changes within populations◦ Microevolution◦ Gene is the object of selection◦ Mutations lead to saltational speciation
Naturalists◦ Studied biodiversity and origin of new taxa◦ Macroevlolution◦ Properties in individuals are objects of selection◦ Speciation is a gradual accumulation of changes
First what was well accepted? ◦ Change in organisms occurs over time◦ The branching theory implying common descent
What had difficulty being accepted?◦ That evolution was a gradual process◦ That species multiplied (increase in diversity)◦ That natural selection was the means
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.
Geneticists◦ Worked in labs and studied the processes in single
populations◦ Only examined changes within a population-
microevolution ◦ Believed each mutation led to a new species◦ Believed speciation was saltational◦ Gene is the object of selection
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. NaturalistB. Geneticist
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.
◦ Moritz Wagner ◦ Karl Jordan◦ Edward Poulton◦ Sergei Chetverikov◦ Erwin Stresemann◦ Ernst Mayr and ◦ Julian Huxley
A. Thomas Hunt MorganB. Theodosius DobzhanskyC. Ledyard StebbinsD. Ernst MayrE. R. A. Fisher
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. 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
gradually, become separate species. Over more time new higher taxa can emerge.
Selection acts on individuals but has its effects in populations.
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)
John Maynard Smith◦ Extended the Darwinian theory to explanation of animal
behavior Ledyard Stebbins –
◦ did for plant evolution what Dobzhansky with his fruit flies had done for animal evolution
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
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
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.
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
1. Extinct species
The fossil record provides many examples of species that once lived on the earth but are now extinct.
Irish Elk
2. The Law of Succession
Armadillo
Wombat
Glyptodont
Diptotodon
Connection made by Richard Owen
Connection made by Charles Darwin
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
Siberian Greenish Warbler
Pg. 53
Homology
2. Homology from 3 areas
Structural Homology
Developmental Homology
1. Genetic Code is identical in essentially all species
2. Shared flaws in genetic makeup 3. Psuedogenes (CMAH in humans)
Page 57
Shared genetic flaws found in Chimps and Bonobos but not ion Gorillas and Orangutans also
Flaw leads to mistakes
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. Principle of Uniformitarianism2. Geologic time scale\
1. Younger rocks on top of older ones2. Originally in horizontal position3. Rocks that intrude into seams are younger4. Boulders, cobbles are older than the host rock5. Earlier fossil life forms are simpler, more recent
are most similar to extant forms. 3. Radiometric dating4. Dating the earth’s actual age from its
molten state.
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