Darwin

1
Darwins Big Breakthrough Darwin and the Concept
of Natural Selection
2
Galapagos Tortoise
(saddlebacked)
(domed)
Notes that tortoises on different islands have
differently shaped shells (perhaps from common
ancestor but diverged in form due to geographic
isolation
3
Darwins Iguanas
Marine Iguana
Land Iguana
-The marine iguana is grey-coloured and eats
seaweed whereas the land iguana is
brownish-coloured and eats land plants. Both
presumably arose from a common ancestor, but
adapted to different environments
4
Darwins Finches
seed crushers
biters
probers
Again, all of these are related and must have
come from common ancestor, but adapted to
different conditions/needs.
5
Mechanism for Evolutionary Change ?
Seed of an idea planted by Thomas Malthus An
Essay on the Principle of Population (concept of
struggle for existence) Populations must be
kept in check by famine, war, disease otherwise
they grow too large to be supported. (there are
winners and losers)
6
Charles Lyell Principles of Geology (uniformitar
ianism, deep time) Tiny changes over a long
period of time amount to large changes
7
Thomas Henry Huxley (Darwins Bulldog)
-British anatomist and physical anthopologist was
one of Darwins most fervent supporters -promoted
the concept of natural selection in his book as
to Man's Place in Nature (1863)
8

• Abstract on Natural Selection in 1842
• Marries Emma Wedgewood
• Receives essay by Alfred Russel Wallace on
  studies in Brazil
• (similar conclusions as Darwins)
• Joint presentation by Darwin and Wallace
• before Linnean Society
• On the Origin of Species published 1859
• Rebuttal before British Association for the
• Advancement of Science in 1860
• (Oxford Bishop Samuel Wilburforce opposes
  Darwin)
• - Huxley supports Darwin
• The Descent of Man and Selection in Relation to
  Sex
• published in1967
• Darwin dies in 1882

9
Principles of Natural Selection 1. All living
things vary 2. All living things tend to produce
many offspring 3. Numbers of species tend to
remain constant
Deductions 1. There is a struggle for
existence 2. In this struggle, only the fittest
survive
Herbert Spencer (reporter) -- survival of the
fittest
10
End of Lecture