Evidence for Evolution

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Chapter 19

• Evidence for Evolution

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Evolutionary Tree of Life

• Phylogenies
• Diagrams of lineage or evolutionary relationships
  among species
• Diagram of how ancestral species became diverse
  and branched into different species over time
• How did scientists develop tree of life?
• Cladistics
• Study of evidence to create phylogeny

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Phylogenies
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What is the most common evidence of past life?

• Fossils
• What is the study of (fossil) evidence of past
  life called?
• Paleontology
• Researchers also study anatomy, physiology,
  behavior and DNA to develop theories of change

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Fossils
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Fossil Dating

• 2 methods
• Relative Dating age relative to other fossils
  in strata
• Based on principle of superposition older
  fossils lower in rock strata
• Radiometric Dating using natural radioactivity

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Radiometric Dating

• Uses isotopes
• Different numbers of neutrons
• Certain isotopes are unstable so emit radiation
• Thus change to different isotope or element
• Half-life time it takes for ½ of the isotopes
  to decay to the other form
• If know half-life and amounts of before and after
  forms in sample, then can deduce age

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Comparing anatomy and biochemistry in modern
species

• 1. Comparative Anatomy
• Homologous structures similar structures in
  different types of organisms
• Example forelimbs vertebrates
• Analogous structures similar function but no
  similar structure
• Example Wings of bats vs. insects
• Vestigial structures having no obvious function
• Example Appendix of humans
• Comparative embryology
• Example Similarities in vertebrate embryos

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Analogous Structures
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Eye sockets in blind salamanders
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Comparing anatomy and biochemistry in modern
species

• 2. Molecular Evolution
• What is the assumption?
• Greater the molecular similarities closer the
  evolutionary relationship
• Highly conserved protein or nucleic acid
  sequence that is very similar in different species

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How do we measure species relatedness at
chromosomal level?

• Number of chromosomes
• Chromosome banding patterns
• Gene order- to identify regions of synteny
  identical sequences of genes along chromosomes

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Chromosome banding
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And Relatedness at the Gene Level?

• A. Protein Sequences
• Many organisms use the same proteins
• Examples Cytochrome C part of electron
  transport chain of cell respiration
• All eukaryotes have 20 of the 104 AAs in
  identical positions
• The more alike 2 species, the more alike the AA
  sequence in cytochrome C

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B. DNA Sequences

• Pieces of are DNA sequenced and used to
• Estimate a genes importance
• Determine the protein produced
• Determine animal model to medical research
• DNA hybridization
• Estimating the similarity of the genomes of two
  species
• The faster DNA from 2 species forms a double
  helix together, the more similar they are
• Humans differ in 1.8 of base pairs from chimps,
  2.3 from gorillas and 3.7 from orangutan

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DNA Sequencing

• ATT TGC TTC TGA CAC AAC TGT GTT CAC TAG CAA CCT
  CAA ACA GAC ACC ATG GTG CAC CTG ACT CCT GAG GAG
  AAG TCT GCC GTT ACT GCC CTG TGG GGC AAG GTG AAC
  GTG GAT GAA GTT GGT GGT GAG GCC CTG GGC AGG CTG
  CTG GTG GTC TAC CCT TGG ACC CAG AGG TTC TTT GAG
  TCC TTT GGG GAT CTG TCC ACT CCT GAT GCT GTT ATG
  GGC AAC CCT AAG GTG AAG GCT

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Molecular tree diagrams

• Phylogenies depictions of evolutionary
  relationships
• Based on molecular evidence
• DNA sequences
• Protein sequences
• DNA hybridization

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