Descent with Modification

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Descent with Modification

• Natural Selection A population can change over
  time if individuals have heritable traits that
  leave more offspring than others
• Natural selection results
  in evolutionary adaptation
  enhancing an organisms
  survival and reproduction
• Evolution is biological
  change over time

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The Historical Context for Evolutional Theory

• Charles Darwins book, The Origins of Species,
  rocked the world!
• It challenged prevailing scientific views
• It challenged a worldwide view that had been
  taught for centuries, such as
• The Earth is only a few thousand years old
• The Earth is populated by unchanging forms of
  life that has been individually made during the
  single week in which the Creator formed the
  entire universe.

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Theories of Geologic Gradualism

• Study of fossils in sedimentary rock, fossil
  species that are deeper in the stratum are more
  dissimilar from modern species
• Gradualism profound change in the cumulative
  product of slow but continuous processes.
• Darwin concluded Earth must be very old
• Several slow and subtle processes can add up to
  substantial change

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Early Theories of Evolution

• Jean Baptiste Lamarck
• Theory of use and disuse body parts that were
  used more grew bigger and stronger those that
  were not would deteriorate. Ex. giraffes neck
  and fiddler crabs claw

• Inheritance of acquired characteristics
  modifications and organism acquired during its
  life could be passed down to its offspring. Ex.
  with much use, the giraffes neck grows longer
  and this long neck is passed down to its offspring

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Scientists who influenced Darwin

• Lyell
• Principles of Geology
• Plant and animal species emerged, developed
  variations and then became extinct

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Scientists who influenced Darwin

• Malthus- populations outgrew their food supplies
  causing competition

Essay on the Principle of Population (1798)
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The Darwinian Revolution

• Charles Darwin (1809 1882)
• At age 16 Darwin went to medical school, but
  found it boring and distasteful
• In 1831, Darwin set sail around the world on the
  HMS Beagle as the ships naturalist

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The Darwinian Revolution

• Darwin noted that animals living on the Galapagos
  Islands live nowhere else in the world although
  they resemble those on South Americans mainland.
• Origin of new species and adaptation to
  environment are closely related

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The Darwinian Revolution

• By the 1840s, Darwin had already established his
  theories of natural selection
• In 1859, he published The Origin of Species
• He did not use the word evolution ? instead he
  used descent with modification
• Evolution is an explanation for lifes unity and
  diversity
• Natural selection is the cause of adaptive
  evolution
• 99 of all species that ever lived are extinct

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The Darwinian Revolution

• Darwins Main Ideas
• Natural selection is differential success in
  reproduction
• Tendency towards overproduction
• Not all offspring survive (struggle for survival)
• Variations exist and are inherited
• Those best suited to their environment will live
  longer and leave more offspring
• Favored traits disproportionately represented in
  the next generation thus the population changes
  as a whole
• Artificial selection supports these claims

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Some Subtleties of Natural Selection

• Populations evolve, not individuals
• Heritable variations are amplified or diminished
  (must be a heritable variation)
• Situational some adaptations may be
  advantageous in one environment and detrimental
  in another

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More Examples of Natural Selection

• Evolution of insecticide resistance in hundreds
  of insect species
• Evolution of antibacterial resistance in bacteria
  species

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Evidence for Evolution

• 1. Fossils
• 2. Comparative anatomy
• 3. Comparative embryology
• 4. Biochemistry
• 5. Genetic evidence
• 6. Direct evidence

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Fossils

• FOSSILS
• mold or cast of organism left in rock, fossilized
  bone and teeth
• life becomes more complex over time
• record is incomplete

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Evidence for Evolution

• RELATIVE DATING
• layers in rock bed used to date organisms

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Evidence for Evolution

• PHYLOGENY- description of
  the lines of descent of organisms as they
  lived through history.

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Other Evidence of Evolution

• HOMOLOGY similarity in characteristics
  resulting from common ancestry
• Anatomical
• Homologous structures have the same structure,
  but different functions
• Vestigial organs structures of marginal, if
  any, importance to the organism
• Embryological
• All animals have similar embryonic stages
• Molecular
• Comparing DNA and RNA to determine how related
  species are to another

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Comparative AnatomyHomologous structures
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Vestigial Organs
Vestigial Remains of a Pelvic Girdle in a Whale
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Comparative Embryology

• the study of developing plants and animals
• Below is the pictures of embryos for a CHICKEN,
  FISH, HUMAN, RABBIT, and TORTOISE . Can you guess
  which one is each type of organism?
• 1 2 3
  4 5

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Comparative EmbryologyComparative Embryology-
The complete picture
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Evidence for Evolution

• Genetic Evidence
• Mutations- mistakes in the genetic code
• Causes changes in populations over time
• Population genetics- researchers use mathematical
  descriptions of genetic make ups to help them
  trace evolutionary trends within populations
• Selective Breeding- humans choose plants/animals
  with most desirable traits and breed them to
  pass those traits to offspring

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Evidence for Evolution

• Direct Evidence
• Rapid Evolution
• Strains of bacteria becoming resistant to
  antibiotics
• Weeds and herbicides
• Insects and insecticides

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Biogeography

• The geographic distribution of a species
• Species tend to be more closely related to other
  species from the same area than to other species
  with the same way of life but living in different
  areas

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Final words

• Absence of evidence is not evidence of absence.
  Charles Darwin