Darwins Theory of Evolution

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Chapter 15

• Darwins Theory of Evolution

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15-1 The Puzzle of Lifes Diversity

• Evolution- Change over time
• Theory- Well supported testable explanation of
  phenomena that have occurred in the natural
  world.
• Voyage of the Beagle
• Charles Darwin contributed the most to our
  understanding of evolution.
• 1831 set sail on he H.M.S. Beagle- around the
  world.
• Collected different specimen

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Darwins Observation

• Patterns of Diversity
• Plants animals well suited for wherever they
  lived.
• Many ways organisms survived reproduced.
• Where different species lived and did not live.
• Living Organisms Fossils
• Collected preserved remains of ancient
  organisms-fossils
• Some looked familiar, others did not.
• The Galapagos Islands
• Islands that were close together had different
  climates.
• Studied land tortoises, marine iguanas, and
  finches.

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The Journey Home

• Characteristics of many animals and plants varied
  noticeably among different islands of the
  Galapagos
• Once back in England, wondered if animals living
  on different islands had once been members of the
  same species.

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15-2 Ideas That Shaped Darwins Thinking

• Early Beliefs were that the earth its living
  species had not changed since the creation of
  earth
• Fossil records helped to challenge this
  traditional view of life.

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An Ancient, Changing Earth

• James Hutton
• Proposed that Earth is shaped by geological
  forces that took place over extremely long
  periods of time.
• Estimated Earth to be millions of years old.

• Charles Lyell
• Explained how geological features could be built
  up or torn down over long periods of time.

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• Lamarcks Theory of Evolution
• Through selective use or disuse of organs,
  organism acquired or lost certain traits during
  their lifetime.
• Traits could be passed on to their offspring.
• Over time, it lead to change in a species.

• Population Growth
• Thomas Malthus
• If the human population continued to grow
  unchecked, eventually there would be insufficient
  living space food for everyone.
• Forces against growth
• War
• Famine
• Disease

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15-3 Darwin Presents His Case

• Published On the Origin of Species
• Natural Variation- different among individuals of
  a species
• Artificial Selection- man selects certain
  favorable traits and then breeds animals with
  those traits.

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Evolution by Natural Selection

• Struggle for Existence- members of a species
  compete for food, living space, other
  necessities
• Survival of the Fittest- Individuals who are best
  suited to their environment survive reproduce
  most successfully
• Descent With Modification- Each living species
  has descended, with changes, from other species
  over time.

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Evidence of Evolution

• Fossil Record
• Geographic Distribution of Living Species
• Finches he collected were slightly different.
• Homologous structures
• Structure w/ different mature forms, but develop
  from the same embryonic tissues
• Vestigial organ
• Similarities in Early Development
• Many embryos look similar during the early stages
  of development.

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Summary of Darwins Theory

• Individual organisms in nature differ from each
  other.
• Organisms in nature produce more offspring's than
  will survive.
• Members of species must compete for resources.
• Each organism is unique.
• Those best suited to their environment survive
  reproduce most successfully.
• Species Change over time.
• Species today have descended w/ modification from
  those in the past.
• All organisms on Earth are united into a single
  tree of life by common descent.