Darwin

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Darwins Theory of Evolution
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16.1 Darwins Voyages of Discovery

• Definition of Evolution
• Change in a kind of organism over time.
• Process by which modern organisms have descended
  from ancient organisms.
• In biology, the noun evolution means the process
  by which organisms have changed over time.
• The verb evolve means to change over time.

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Darwins Epic Journey

• Individual who contributed the most to our
  understanding of evolution.
• In 1831, he set sail from England for a voyage
  around the world.
• He developed a scientific theory of biological
  evolution that explains how modern organisms
  evolved over long periods of time through descent
  from common ancestors.

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• Darwin was a naturalist aboard an exploration
  ship called the HMS Beagle.
• Collected and catalogued biological specimens for
  return to England.

Charles Darwins BookThe Origin of Species /
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 Darwins Voyage
Section 15-1
On a 5 year voyage on the H.M.S.Beagle, Darwin
visited several continents and many remote
islands. Watch Video2 PBS
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Observations Aboard the Beagle
What 3 patterns of biodiversity did Darwin
Note? 1. Species vary globally. 2. Species vary
locally. 3. Species vary over time. Refer to
Figures 16-1, 16-2, 16,3
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Species Vary Globally
Read Page 451
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Species Vary Locally
Read Page 452
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Species Vary Over Time
Read Page 452-453
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16-2 Ideas That Shaped Darwins Thinking

• Hutton and Lyell Refer to Fig. 16-4 and 16-5
  Read Pages 454 - 455
• Jean Baptise Lamark Refer to Fig 16-6
• Read page 456
• Thomas Maltus Refer to Fig 16-7
• Read page 457

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Lamarcks Theory of Evolution

• Jean-Baptise Lamarck was among the first
  scientists to recognize that living things have
  changed over time and that all species were
  descended from other species.
• He proposed that by selective use or disuse of
  organs, organisms acquired or lost certain traits
  during their lifetime.
• These traits could then be passed on to their
  offspring. This process led to change in a
  species.

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Lamarcks Theory of Evolution
Section 15-2
Refer to Page 459 Discuss Artificial Selection
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Lamarck vs. Darwin
Lamark vs DarwinVideo
What is the Theory of Evolution
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16-3 Darwin Presents His Case

• Evolution by Natural Selection
• Struggle for existence - members of each species
  compete regularly to obtain food, living space,
  and other necessities of life.
• Variation and Adaptation - any heritable
  characteristic that increases an organisms to
  survive and reproduce in its environment is
  called an adaptation. Fig 16-9
• Survival of the Fittest - process by which
  individuals that are better suited to their
  environment survive and reproduce most
  successfully also called natural selection.
• Natural Selection Occurs in any situation in
  which more individuals are born that can survive
  (struggle for existence), there is natural
  heritable variation (variation and adaptation),
  and there is a variable fitness among individuals
  (survival of the fittest)

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The Struggle for Existence Organisms produce
more offspring than can survive. Grasshoppers can
lay over 200 eggs at a time. Only a small
fraction of these offspring survive to reproduce.
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Variation and Adaptation There is variation in
nature, and certain heritable variationscalled
adaptationsincrease an individuals chance of
surviving and reproducing. In this population of
grasshoppers, heritable variation includes
yellow and green body color. Green coloration is
an adaptation Green grasshoppers blend into
their environment and so are less visible to
predators.
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3 Survival of the Fittest Because their green
color serves to camouflage them from predators,
green grasshoppers have a higher fitness than
yellow grasshoppers. This means that green
grasshoppers survive and reproduce more often
than do yellow grasshoppers in this environment.
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Peppered Moth Simulation
Natural Selection Green grasshoppers become more
common than yellow grasshoppers in this
population over time because (1) more
grasshoppers are born than can survive, (2)
individuals vary in color and color is a
heritable trait, and (3) green individuals have a
higher fitness in their current environment.
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Common Descent
Descent with modification refers to the passing
on of traits from parent organisms to their
offspring. This passing on of traits is known as
heredity, and the basic unit of heredity is the
gene. Genes hold information about every
conceivable aspect of an organism its growth,
development, behavior, appearance, physiology,
reproduction.
Natural Selection Video
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16-4 Evidence of Evolution

• Biogeography study of where organisms live now
  and where they and their ancestors lived in the
  past.
• Closely related but different
• Distantly related but similar

Fossilized Dinosaur Heart
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The Age of Earth and Fossils

• The Age of Earth
• Recent Fossil Finds Refer to Fig 16-13

Fossilized Dinosaur Heart
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Comparing Anatomy and Embryology

• Homologous Structures Fig 16-14
• Analogous Structures
• Vestigial Structures Fig 16-15
• Embryology

Fossilized Dinosaur Heart
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Homologous Structures

• Refers to the fact that organisms' structures are
  formed from similar anatomy.
• Example the wing of a bird, arm of a man, wing of
  a bat, and flipper of a whale, all appear to be
  formed from a common set of bones.
• Implies that these organisms evolved from some
  common ancestor

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Homologous Limb Bones
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Analogous Structures
Common structure, not common function
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Vestigial Structures

• Refers to the fact that organisms have structures
  which are disused
• These structures, however, are remnants of
  structures the organisms used earlier in their
  evolutionary history.
• Examples
• Hip bones in whales
• Tail in humans
• Appendix in humans
• Legs/hips in snakes

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Vestigial Structures
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Similarities in Embryological Development

• In early embryological development, it appears
  that embryos "play out" their evolutionary
  history.
• Implies that genetically, we have not "forgotten"
  our evolutionary history, only built upon it.
• Interactive Activity Guess the Embryo

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How do we know evolution happens?

• See how different lines of evidence contribute to
  our picture of evolution. Learn about the fossil
  evidence for whales' land-dwelling ancestors.
• Video 3 PBS
• Evidence for Evolution Video