Download Evolution is the phenomenon of modification with descent (it is not

Big questions in evolution
Evolution is the phenomenon
of modification with descent
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Why do species change?
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How do new species arise?
(it is not natural selection)
Hawaiian Drosophila
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A (very brief) history of evolutionary thought
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Hyracotherium (50MY)
Why do species go extinct?
Darwin and the Beagle: 1831-36
Aristotle and Plato
– Archetypes (i.e. no evolution, variation is meaningless)
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Buffon, Cuvier, Smith
– Importance of fossils. Earth may be old.
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Hutton, Lyell
– Current geological processes can explain earth, but only on a long time-scale
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Lamarck and Erasmus Darwin
– Transmutationism
– Inheritance of acquired characeteristics or ‘use and disuse’
– Universal common ancestor
<<insert picture p432 Campbell>>
Equus
What Darwin said
Darwin’s finches
Geospiza
Organisms produce too many offspring
Heritable differences exist in traits influencing the
adaptation of an organism to its environment
Organisms that are better adapted have a higher chance of
survival
Also Alfred Russell Wallace – letters to Darwin prompted publication of ‘On the Origin of Species’
The Huxley – Wilberforce debate
Arguments against Darwin
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Biblical
– Earth is only about 4000 years old
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Tautological
– Which are the fitter organisms? Those which survive.
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Paley’s blind watchmaker
– How can complex structures arise by a ‘blind’ process?
I asserted - and I repeat - that a man has no reason to be ashamed of having an ape for
his grandfather. If there were an ancestor whom I should feel shame in recalling it would
rather be a man-a man of restless and versatile intellect-who, not content with an
equivocal success in his own sphere of activity, plunges into scientific questions with
which he has no real acquaintance, only to obscure them by an aimless rhetoric, and
distract the attention of his hearers from the real point at issue by eloquent digressions
and skilled appeals to religious prejudice.
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The problem of heredity
– How can natural selection work?
Gradualist steps in the origin of the molluscan eye
What is the evidence for evolution?
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The fossil record
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Origin of diversity
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Continuity of form
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Simultaneous shifts in climate and fossil fauna
Darwin and heredity
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Darwin viewed heredity as a blending process
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BUT blending inheritance removes variation which is essential for natural
selection
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Francis Galton’s law of heredity attempted to provide a mathematical basis for
Darwin’s views (later reinterpreted by Karl Pearson)
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Major controversy in the early 1900s arose between those who supported
Darwin’s view and those (led by Galton) who rejected them
The fossil record – different forms of life
Ediacara
Burgess Shale
Direct observation
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Industrial melanism
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Drug resistance
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Experimental
Species complexes
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Hybrid zones
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Ring species
Dickensonia
~ 550 MY
Marella
~ 500 MY
Homology
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Similarity through common descent
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From anatomy to molecular biology
Burgess shale
Fossils –
continuity of
form
How are fossils formed?
Homo erectus
1.8 MY
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unaltered preservation
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permineralization=petrification
– like insects or plant parts trapped in amber, a hardened form of tree sap
Homo sapiens (early form)
0.18 MY
– in which rock-like minerals seep in slowly and replace the original organic
tissues with silica, calcite or pyrite, forming a rock-like fossil - can preserve
hard and soft parts - most bone and wood fossils are permineralized
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replacement
– An organism's hard parts dissolve and are replaced by other minerals, like
calcite, silica, pyrite, or iron
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carbonization=coalification
– in which only the carbon remains in the specimen - other elements, like
hydrogen, oxygen, and nitrogen are removed
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recrystalization
– hard parts either revert to more stable minerals or small crystals turn into
larger crystals
Homo sapiens (modern)
0.01 MY
Evolution in action I – Industrial melanism
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authigenic preservation
– molds and casts of organisms that have been destroyed or dissolved
Evolution in action II – Drug resistance in HIV
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RT inhibitors
– Block reverse transcription
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Nucleotide RT inhibitors
– Chain terminating nucleotide analogs
– Some escape mutations avoid incorporating altered bases
– Others can excise them if incorporated
– In absence of drug modifications are deleterious
Frequency of melanic form in England
(1959-1995)
Melanic and wild-type Biston betularia
– Compensatory mutations can occur which reduce/remove deleterious effect
Ring species
Homology – inference of shared ancestry
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Continuously interbreeding forms between two or more separate species
– e.g. Ensatina salamanders in California
Structures similar by descent
– wings of birds and bats homologous to arms of humans and flippers of
dolphins
– subunit alpha- and beta-globin in haemoglobin similar through descent
3D alignment of protein structures
http://www.elcomsoft.com/3dpaln.html
Is species change inevitable?
Further controversies in the evolution debate I
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Gradualist v punctuated?
– Fossil record shows abrupt changes of form separated by long periods of
stasis
– ‘Punctuated Equilibrium’ – Gould and Eldridge
Coelocanth
– BUT fast in fossil record is millions of years
– Fossil record very patchy
– Gradualist evolution can occur fast (e.g. Homo sapiens)
Dicksonia
tree fern
Tuatara
Further controversies in the evolution debate II
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The influence of physical properties
– Is the course of evolution an emergent property of the nature of complex
systems governed by simple laws?
– Emergent properties/self-assembly