Evidence of Evolution

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Evidence of Evolution
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Evidence of Evolution

• Darwin argued that living things have been
  evolving on Earth for millions of years.
• Evidence supporting his theory could be found
• 1. Fossil record
• Geographical distribution of living species
• Anatomy
• 4. Similarity in early development (embryology)

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1. The Fossil Record

• Darwin saw fossils as a record of the history of
  life on Earth.
• Darwin proposed
• Earth was millions, rather than thousands, of
  years old
• Countless species had come into being, lived for
  a time, and then vanished.

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2. Geographic distribution of Living Species

• Species now living on different continents had
  each descended from different ancestors.
• Some animals on each continent were living under
  similar ecological conditions so they were
  exposed to similar pressures of natural selection.

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Similar, But Unrelated Species
As a result, Darwin concluded that because of
these similar selection pressures, different
animals ended up evolving certain features in
common!
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3. Anatomy

• Darwin noticed similarities among the body parts
  of various animal and plants.
• There are three different types of structures to
  help support Darwin's Theory of Evolution.
• Homologous Structures
• Analogous Structures
• Vestigial Structures

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Homologous Structures

• Homologous Structures
• Structures that are similar and have originated
  from a common ancestor.
• May look different on the outside, but have
  similar structure inside.
• Indicates that organisms may have shared a recent
  common ancestor.

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Homologous Structures contd.

• The limbs of different organisms serve different
  functions, but have the same bone structure
  inside.

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Analogous Structures

• Analogous Structures
• Structures that serve identical functions, but
  have different internal anatomy.
• Ex wings of birds and insects
• Both allow organisms to fly, but have different
  development and structure.
• Shows a more distant relationship than homologous
  structures.

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(No Transcript)
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Identify the following structures as analogy or
homologous. Be able to defend your answer!
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Vestigial Structures

• Vestigial structures that were useful in
  ancestors but are no longer used by modern
  organisms
• Shows relationship between organisms with
  vestigial structure and those with a working
  version.
• Ex humans have tailbones homologous to tails of
  other animals

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Vestigial Structures contd.

• Some organisms have genes that are conserved.
• Genes that have remained unchanged, but may be
  turned off.
• Ex whales have genes for hind legs
• Can give clues about early development of a
  species.
• Ex whales may have descended from an ancestor
  who lived on land

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4. Embryology

• Embryology study of early development
• Many organisms share similarities within the
  early stages of development.
• The same groups of embryonic cells develop in the
  same order and in similar patterns to produce the
  tissues and organs of all vertebrates.
• These common cells and tissues, growing in
  similar ways to produce the homologous
  structures!
• Can indicate a common ancestry among different
  species.

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Embryology contd.
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Similarities in Macromolecules

• Similarities within DNA, RNA and proteins of
  different species
• Genetic code is universal all living things
  share the same code
• Closely related species have very similar gene
  sequences and protein sequences.
• Ex hemoglobin in humans and gorillas differs by
  only 1 amino acid
• Can confirm ideas suggested by anatomy and
  embryology.