1:Evolution Prof Rod Page

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1EvolutionProf Rod Page Dr Ruedi Nager

• Lectures 1-2 Evidence for Evolution
• Lectures 3-4 The process of selection
• Lectures 5-6 Origins of species

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Lecture Notes Online
Taxonomy.zoology.gla.ac.uk/rdmp1c/teaching/L1/Evo
lution
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3 Definition
'Evolution' is a description of AND an
explanation of the history of species - their
origins, how they change, survive, become
extinct. So evolution concerns BOTH a
historical account of life on earth AND an
attempt to explain how observed changes have
happened.
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4 Overview of Lectures 1 2

• Evidence that evolution has occurred
• Comparative anatomy
• Taxonomy
• Geology and fossils
• Biogeography

• How does evolution occur?
• Malthus and natural selection
• How does perfection arise?
• How does novelty arise?

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5A changing world view (200-300 years ago)
Earth is young In the 17th century Archbishop
James Ussher used the Bible to date the origin of
the earth as 4004 B.C. (Vice-chancellor of
Cambridge refined this to the morning of Sunday,
October 23rd, 4004 B.C.) Fixity of
species Species are permanent, natural kinds.
They do not change. A fixed plan of
creation. Design Living things seem designed
for a purpose, and a design implies a designer
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6 A changing world view
Earth is ancient Approximately 4,500,000,000
years old (radioactive isotopes) Species
evolve Living things are constantly changing,
new species arise and others go extinct The
history of life is contingent Adaptation Fit
between organisms and their environment is due to
natural selection (blind watchmaker) Organisms
are often imperfectly created
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7 Darwins place in science
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Unity of Nature
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9 Life is constructed on a similar plan
Human and chimpanzee facial expressions
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10 Life is constructed on a similar plan
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11 Vestigial organs
The eye bulbs of blind, cave-dwelling creatures,
such as the grotto salamander (Typhlotriton
spelaeus).
The anthers and pollen of asexual dandelions.
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12 Vestigial organs in humans
Appendix
Nictating membrane in eye
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13 Hind limbs in whales
Whale embryo
Fossil whale
Modern whale
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14 Human embryo at 5 weeks
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Ontogeny
http//www.pbs.org/wgbh/nova/odyssey/clips/
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16 Comparative anatomy and embryology

• A group of organisms is similarly constructed no
  matter how they live (homologous structures)
• Organisms show traces of previous stages in their
  development (ontogeny)
• Vestigial structures - reduced structures with no
  apparent function

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Taxonomy
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18 Scala Naturae(scale of nature)
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19 Linnean classification of the domestic
cat(Felis silvestris) and common buttercup
(Ranunculus acris)
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20 Linnean Hierarchy is Tree-like
Carnivores
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Geology
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21 Three views of geology
Gradualism (Hutton) Profound changes can be the
result of small changes over long periods of
time.
Catastrophism (Cuvier) Recurrent catastrophic
events causing widespread extinction and
resulting in sharp boundaries between fossil
layers.
Uniformitarism (Lyell) The same processes we see
today also acted in the past
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22 Age of the Earth
The depth of the sedimentary column implies that
the Earth is old (it would take a long time to
accumulate these layers gradually)
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23 Lord Kelvin and the Age of the Earth

• Leading physicist of 19th Century
• (absolute temperature scale named after him)
• Argued from rate of cooling of the Earth that it
  was about 98 Myrs old
• Similar result from estimating the age of the sun
• Darwin estimated the Sussex Weald cliffs had
  taken 300 Myr to form

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23a Resolution(what Kelvin didnt know)

• The source of the Suns energy is nuclear fusion
• The earth has a molten core due to radioactive
  decay

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Fossils

• (the other evidence from geology)

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Whale evolution(terrestrial to aquatic in 8
Myr)
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25Pakicetus (50 Myr ago in Pakistan)
50 Myr old fossils of Pakicetus (large animal)
and Ichthyolestes (small animal) from Pakistan
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26Rodhocetus (47 Myr ago in Pakistan)
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27Transitions in the fossil record Foraminifera
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Biogeography
When on board H.M.S. Beagle, as naturalist, I
was much struck with certain facts in the
distribution of organic beings inhabiting South
America, and in the geological relations of the
present to the past inhabitants of that
continent.
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29 Biogeography
Organisms in different areas are different, even
if they occupy the same "niche"
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30 Similar environment, different species
Northern Hemisphere
Puffins and auks
Southern Hemisphere
Penguins and petrels
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Summary

• Comparative anatomy - living things are
  constructed along the same lines
• Taxonomy - life is hierarchical (tree of life)
• Geology - Earth is ancient, fossils record
  evolution, small changes can have big effects
• Biogeography - same environment yields different
  organisms