EVIDENCE OF EVOLUTION

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EVIDENCE OF EVOLUTION
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Key Concepts

• What evidence supports the theory of evolution?
• How do scientists infer evolutionary
  relationships among organisms?
• How do new species form?

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Key Terms

• Homologous Structures
• Body parts that are structurally similar in
  related species.

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Key Terms

• Branching tree
• A diagram that shows how scientists think
  different groups of organisms are related.

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Identifying SupportingEvidence

• Identifying supporting evidence helps us
  understand the relationship between the facts and
  the hypothesis.
• Evidence consists of facts that can be confirmed
  by testing or observation.

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Supporting Darwins Theory

• Fossils show that organisms that lived in the
  past were very different from organisms alive
  today.
• Patterns of early development show that some
  different organisms look similar during their
  early stages.
• Similar body structures in different species show
  that the organisms shared a common ancestor.

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Interpreting the Evidence

• FOSSILS
• EARLY DEVELOPMENT
• BODY STRUCTURE

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FOSSILS

• The preserved remains or traces of an organism
  that lived in the past.
• Fossils show that organisms that lived in the
  past were very different than organisms alive
  today.
• Scientists use fossils to infer the structures of
  ancient organisms.

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EARLY DEVELOPMENT(embryology)

• Scientists compare the early development of
  different organisms to make inferences about
  evolutionary relationships.
• Similarities in early development among different
  organisms suggests that they are related and
  share a common ancestor.

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BODY STRUCTURE(homologous structures)

• Darwin compared body structures of living species
  when observing the species on the Galapagos
  Islands.
• Body structure is an organisms body plan, how
  its bones are arranged.
• Similarities in body structure provide evidence
  that organisms evolved from a common ancestor.

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Species Relationships

• Fossils, early development patterns, and body
  structure provide evidence that evolution has
  occurred.
• Scientists also have used these kinds of evidence
  to infer how organisms are related to one
  another.

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New Evidence

• DNA
• Protein Structure

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Similarities in DNA

• Scientists compare the genes of different species
  to determine how closely related the species are.
• The more similar the sequence of bases in the
  DNA, the more closely related the species are.
• The more similar the order of amino acids (codes
  for proteins) in the DNA, the more closely
  related the species are.

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Combining Evidence

• The use of DNA and protein structure has
  confirmed conclusions that scientists had already
  based on fossils, embryos, and body structure.
• The use of DNA and protein structure has also
  caused scientists to revise the branching trees
  of some species.

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Branching Trees

• Branching trees show common ancestry (phylogeny).
• Evolution is about gradualism and phylogeny.

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How Do New Species Form?(speciation)

• A new species can form when a group of
  individuals remains isolated from the rest of its
  species long enough to evolve different traits.
• Isolation/Separation
• River
• Volcano
• Mountain range

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Convergent Evolution

• The process whereby organisms not closely
  related, independently evolve similar traits as a
  result of having to adapt to similar environments
  or ecological niches.

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Divergent Evolution(adaptive radiation)

• The process by which related species evolve
  different traits.

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Gradualism

• Evolution occurs
• slowly but steadily.