Evolution

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Evolution

• Lesson 1
• An Introduction to Charles Darwin and the Nature
  of Science

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• A scientist, however, gifted, can be compared
  with a fly crawling on the inside wall of a
  cathedral if it could draw what it sees, the
  flys picture of the cathedral would be as crude
  as early maps of the world if it could voice its
  speculations about the size, appearance, and
  purpose of the cathedral, the flys opinions
  would be received even more guardedly.
• -- Frederick Aicken, The Nature of Science ,
  pp.29-30

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Evolution As An Idea If I were to give an
award for the single best idea anyone has ever
had, Id give it to Darwin, ahead of Newton and
Einstein and everyone else. In a single stroke,
the idea of evolution by natural selection
unifies the realm of life, meaning and purpose
with the realm of space and time, cause and
effect, mechanism, and physical law. But it is
not just a wonderful idea. It is a dangerous
idea. Daniel Dennet
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Evolution as an Idea

• Evolution is one of the most powerful ideas ever
  to emerge from science. It is the very foundation
  of biology and the key to understanding our own
  human origins. The mechanism of evolution helps
  determine who lives, who dies, and who gets the
  opportunity to pass on traits to the next
  generation. At the same time, evolution ranks as
  one of the most widely misunderstood scientific
  principles in America today.
• Richard Hutton, Executive Producer, Evolution
  WGBH
• Jody Patton, Executive in Charge, Clear Blue Sky
  productions

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Darwins Voyage of Discovery
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Galapagos Islands
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Galapagos Islands
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Figure 22.6 Galápagos finches
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Darwin and the Galapagos

• Consider the following
• How did the Galapagos Islands get there?
• How did the first plants get there?
• How did the first animals get there?
• What is ecological succession?

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Ecological Succession

• process in which communities of plants and animal
  species in a particular area are replaced over
  time by a series of different and often more
  complex communities.
• Two stages
• Primary succession
• Secondary succession

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Primary Succession

• succession in a bare area (no mature soil) that
  has never been occupied before

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Secondary Succession

• succession in an area in which natural vegetation
  has been removed or destroyed but the soil remains

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Ecological Succession
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Darwins Theory of Natural Selection

1. Variations exist
2. These variations are heritable
3. Some variations are advantageous and some are
   disadvantageous
4. Organisms compete for limited resources
5. Organisms with advantageous variations survive
   and reproduce most successfully, leafing more
   organisms like them in the next generation
6. Over time, the population changes to become more
   like the organisms with advantageous variations
7. Todays species have descended from past species
8. All organisms are related and are members of a
   single tree of life

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Examples of Natural Selection

• English Peppered Moth

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Darwin's Finches
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Darwins Theory of Natural Selection

• Individual organisms differ variation is
  heritable
• Organisms produce more offspring than can
  survive they compete for limited resources
• Some variations are advantageous individuals
  best suited to their environment survive and
  reproduce successfully
• Species alive today descended with modification
  from ancestral species that lived in the past

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Darwins Tree of Life
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Evolutionary Classification Using Cladograms

• Cladogram diagram used to show the evolutionary
  relationship between organisms
• Cladograms are constructed using derived
  characteristics
• Derived characteristics - characteristics that
  appear in recent parts of the lineage but not in
  older members new characteristics that evolve
  over time
• Each branch or junction shows the appearance of a
  new trait
• Cladograms demonstrate when characteristics first
  appeared

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Cladogram of vertebrates
http//www.emc.maricopa.edu/faculty/farabee/biobk/
cladogram_1.gif
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http//biology.unm.edu/ccouncil/Biology_203/Summar
ies/Phylogeny.htm