Chapter 19: Change in Species

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Chapter 19 Change in Species

• What evidence exists to support evolution?

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Scientific Fields that Support Evolution

• Paleontology study of fossils
• Anatomy physiology study of body systems and
  structures
• Genetics study of DNA/genes
• Developmental biology study of embryos
  development
• Physical anthropology study changes in humans

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19.1 Fossil Evidence

• Fossils physical remains of ancient organisms
• Fossils largest piece of evidence for evolution

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19.1 Fossil Evidence

• Paleontology the study of fossils
• How do fossils offer information about change?

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19.1 Fossil Evidence

• How do fossils offer information about change?
• They are a record of organisms that are extinct.
• Ancestral relationships can be based on where
  they are found in relation to another fossil.

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19.1 Fossil Evidence

• How do fossils offer information about change?
• They can show us the rate of evolutionary change.
• They are a clue to the physical structure of
  living things (clues to behavior).

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19.2 Ecology Homologies

• Homologous structures similarities between
  species that suggest common ancestry
• Homologies help biologists understand the history
  of evolutionary changes

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Example Forelimbs of vertebrates
Shows evidence that these organisms have an
ancestor in common.
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Example Mouse/Fruit fly eyes
Gene homologies Scientists put the gene coding
for eyes in mice into an eyeless fruit fly
chromosome the fly grew eyes
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Other Evidence for Evolution

• Vestigial Structures
• Structures that are no longer useful in an
  organism (ex appendix, goosebumps, body hair,
  etc. in humans)
• Shows changes in organisms over time our
  distant relatives needed them for something but
  over time they no longer are needed

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19.3 Genetic Molecular Evidence

• Darwins problem explaining how variations are
  inherited
• Study of genetics has provided more support for
  the theory of evolution

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19.3 Genetic Molecular Evidence

• Sources of genetic variation
• Mutation
• Recombination of alleles happens in sexually
  reproducing organisms includes crossing over
  fertilization to produce new combinations of genes

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19.3 Genetic Molecular Evidence

• Genetic variation is the RAW MATERIAL OF
  EVOLUTION!!
• We use molecular data (DNA information) to see
  the degree of relatedness between species more
  DNA in common, more closely related.

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Other Evidence for Evolution

• Embryos
• Early in embryonic development, it is very
  difficult to tell different organisms apart. The
  fact that we start off so similarly is evidence
  we all came from a common ancestor.

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Other Evidence Embryos
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Other Evidence for Evolution

• Skulls
• Used often in human evolution changes in skull
  shape/size show changes in humans over time

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19.4 Process of Speciation

• Speciation the appearance of a new species
• Examples that have been observed primarily in
  bacteria (because they reproduce and so, evolve
  so quickly) new species of grain crossed
  wheat and rye

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19.4 Process of Speciation

• POPULATIONS EVOLVE, NOT INDIVIDUAL ORGANISMS
  WITHIN A POPULATION!!
• Speciation occurs when 2 populations become so
  different in their genetic makeup, they can no
  longer interbreed.

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19.4 Process of Speciation

• Usually occurs as a result of isolation a small
  population that gets isolated from the rest of
  the population develops into its own species.

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19.4 Process of Speciation

• 3 Types of Isolation
• 1. Geographic Isolation most common organisms
  cannot come into contact with one another so they
  cant interbreed (get separated by body of water,
  mountain range, canyon, etc.)

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19.4 Process of Speciation

• 3 types of isolation
• 2. Ecological isolation When two different
  populations adapt to different niches in a habitat

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19.4 Process of Speciation

• 3 types of isolation
• 3. Reproductive isolation (also behavioral) the
  mating patterns of a small group of organisms
  becomes so different from the main group that
  they become reproductively isolated

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19.5 Patterns in Evolution

• Two ideas on Progress of Evolution
• 1. Gradualism Speciation evolutionary change
  occurred through the accumulation of many gradual
  constant changes

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19.5 Patterns in Evolution

• Two ideas on Progress of Evolution
• 2. Punctuated Equilibrium Short period of
  rapid change just after a population becomes
  isolated and forms a new species, after which the
  process slows and approaches stasis

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