Microevolution

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Microevolution

• Evolution Genetic change in a line of descent
  through successive generations.

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Early Beliefs

• Ancient Greeks gods determined human fate
• School of Hippocrates first attempts to find
  natural explanations for observable events.
• In nature, all things are alike in this, in
  that they can be traced to preceding causes.
• Aristotle originally believed that each org was
  distinct from rest later, saw nature as a
  continuum of organization. -- Chain of Being

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New Discoveries

• World is MUCH bigger than originally thought, so
  discovery of orgs was overwhelming when tried to
  place all in Chain.
• Biogeography emerged study of world
  distribution of orgs (raised many more questions)
• Comparative morphology raises questions about
  similarities and differences in body plans of
  major groups embryological similarity (bat
  wing, human arm, whale flipper) and vestigial
  parts (pelvic girdle in snakes)
• Geologists began mapping layers of rocks and
  found similar layers around the world also found
  fossils that raised many more questions about
  sequences and similarities to existing species.

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New Theories

• Georges Cuvier anatomist saw abrupt changes in
  fossil record as corresponding to sedimentary
  discontinuities evidence of changing
  populations?
• These ideas led to his theory catastrophism.
  Was one time of creation that populated the world
  with all species. Global catastrophes destroyed
  many of these orgs. What survived, repopulated.
• Jean Lamarck Inheritance of acquired
  characteristics environmental pressures and
  internal needs bring about permanent changes in
  body form and functioning and offspring inherit
  these changes. (page 376) Ex. Giraffe neck
  increases in length due to need to feed.

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Georges Cuvier
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Jean Baptiste Lamarck
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Figure 22.18 Charles Darwin in 1859, the year
The Origin of Species was published
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Charles Darwin

• Loved outdoors, poor student, studied medicine
  then theology. HATED schoolwork, but fan of
  natural history.
• One of his professors at Cambridge, John Henslow,
  recommended Darwin for position as naturalist
  aboard the H.M.S. Beagle 5 year voyage.
  (1831-1836)

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• On trip, read Charles Lyells Principles of
  Geology -- subtle processes of change were more
  important than catastrophies. Idea of gradual,
  uniformly repetitive change became Theory of
  Uniformity. This challenged thoughts on age of
  earth instead of 6000 yrs, would have taken
  millions of years.
• Darwin began to focus on not only the time
  factor, but more importantly on HOW did species
  evolve in diverse ways.

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Figure 22.x3 Charles Lyell
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Figure 22.5 The Voyage of HMS Beagle
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Darwins voyage and writings

• Spent very little time in the Galapagos Islands,
  but was intrigued by the diversity in such a
  small area.
• Collected thousands of specimens, noted where and
  how collected, and started comparisons aboard
  ship (while suffered from seasickness).
• When returned to England in 1836, talked with
  other naturalists about evidence that life
  evolves.

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• Essay by Thomas Malthus
• a clergyman and economist
• correlated population size with famine,
  disease, and war. Humans run out of resources
  because reproduce too much and must compete for
  their needs.
• Populations grow, and struggle for survival
  ensues war, famine, starvation, sickness.
• ultimate result COMPETITION.

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• Combining all of this with his own notes, came up
  with a set of premises (see page 386 in textbook)
• Nervous about publishing his controversial
  theory, kept reviewing his ideas and searching
  for flaws.
• Not willing to publish until received letter from
  Alfred Wallace who had reached same conclusions.
  Thus, pressured to publish his findings first,
  Darwin relented.
• On the Origin of Species, 1859, detailed
  Darwins evidence in support of evolution.

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Figure 22.x5 Alfred Wallace
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Figure 22.6 Galápagos finches
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Descent with modification
Descent with modification
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Figure 22.1 The historical context of Darwins
life and ideas
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Darwin challenged

• Biggest issues against Darwin were lack of
  missing links transitional forms (Ex.
  Archaeopteryx) and specific explanation of
  gradual evolution by natural selection.
• Darwin did not have a concrete explanation for
  HOW changes could be passed on to offspring
  this took Gregor Mendels work with genetics and
  the garden pea, and then the ideas had to be tied
  together.

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(Paleon.) A fossil bird, of the Jurassic period,
remarkable for having a long tapering tail of
many vertebrae with feathers along each side,
and jaws armed with teeth, with other reptilian
characteristics. 1913 Webster
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