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Evolution. Key Points. Heritable characteristics increase or decrease an organisms chance of survival Evolution is the change of the genetic makeup of a population over time More closely related organisms have more closely related DNA and proteins

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key points
Key Points
  • Heritable characteristics increase or decrease an organisms chance of survival
  • Evolution is the change of the genetic makeup of a population over time
  • More closely related organisms have more closely related DNA and proteins
  • Many organisms have similar structures, and many organisms develop similarly
key points1
Key Points
  • Mutations that lead to evolution occur randomly
  • All species on earth are related by a common ancestor
  • The fossil record shows organisms that are no longer alive
  • Environmental pressures, genetic drift, mutation and competition for resources lead to evolution
how did life on earth begin
How did life on earth begin?
  • There are many theories
  • Information about early earth comes from rocks
  • The earth is ~4.6 billion years old
  • The oldest clues about life on earth are ~3.5 billion years old
  • Fossils are preserved evidence of organisms
  • 99.9% of all organisms are extinct
  • Very few organisms become fossilized
  • Many fossils are casts
    • Minerals fill in the areas where the organism was
dating methods
Dating Methods

Relative Dating

  • A technique where items (rocks or fossils) are dated by comparing the soil layers
  • The Law of Superposition
    • Sedimentary rock is deposited in layers
    • Older layers are deeper
    • Newer layers are on top
  • Explain the picture?
dating methods1
Dating Methods

Radiometric Dating

  • Uses radioactive isotopes to date rocks or organic material
    • Uses the half life of the isotope
  • Carbon-14
    • Decays to Nitrogen-14
    • Half life is 5730 years
    • Can date organisms up to 50,000 years
  • Potassium-40
    • Used to date older items
    • Can only be used to date rocks
    • Half life is 1.3 Billion years
geologic time
Geologic Time
  • Represents major geologic events
spontaneous generation a hypothesis
Spontaneous Generation-A Hypothesis
  • Spontaneous generation- life arises from no life
    • Francisco Redi’s experiment
    • Redi’s experiment opposes the hypothesis
biogenesis a theory
Biogenesis- a theory
  • Biogenesis- life arises from life
  • Louis Pasteur – biogenesis is true for microorganisms
origins of life
Origins of Life
  • Simple organic molecule formation
  • Organic molecules could be synthesized by simple reactions
  • UV light from the Sun and lightning may have been the primary energy source
miller and urey
Miller and Urey
  • Simple organic molecules are made from inorganic molecules
  • Conditions were like that of early earth

Prokaryotes evolved first

    • Archea most closely resemble earth’s first life
    • They are autotrophs, energy does not come from the sun, they do not need oxygen
  • Photosynthesizing prokaryotes evolved next
    • Oxygen was just a byproduct
  • Eukaryotes evolved by prokaryotes developing symbiotic relationships
darwin natural selection
Darwin & Natural Selection
  • Darwin was a naturalist on the HMS Beagle
    • He was also a companion to the captain
    • He collected biological samples
  • Darwin collected many birds, mockingbirds and finches on the Galapagos Islands
    • Each island had similar birds, but they were slightly different
artificial selection and natural selection
Artificial Selection and Natural Selection
  • Humans could changes species such as dogs by artificial selection
  • Darwin’s Hypothesis
    • New species could appear gradually through small changes in ancestral species
natural selection
Natural Selection
  • Individuals in a population show variation
  • Variations are inherited
  • Organisms have more offspring than can survive on the available resources
  • Variations that increase reproductive success will have a greater chance of being passed on
support for evolution
Support for Evolution
  • Fossils
    • Fossils show species that lived long ago
    • Ancient species share similarities with living species



support for evolution1
Support for Evolution
  • Derived traits: newly evolved features that do not appear in common ancestors
    • Feathers
  • Ancestral traits
    • More primitive features that do appear in ancestral forms
homologous structures
Homologous Structures
  • Anatomically similar structures inherited from a common ancestor
    • Structures are used for different purposes
vestigial structures
Vestigial Structures
  • Structures that are reduced in form
    • They are useful in related organisms
  • Features of ancestors that are no longer useful will become smaller or lost over time
analogous structures
Analogous Structures
  • Structures used for the same purpose but are not from a common ancestor
comparative embryology
Comparative Embryology
  • Vertebrate embryos look very similar as embryos
  • Develop differently as they get older
comparative biochemistry
Comparative Biochemistry
  • Common ancestry can be seen in metabolic molecules
    • DNA
    • Amino acid sequences
  • More closely related organisms have similar sequences
genetic drift
Genetic Drift
  • Change in allele frequency
    • Caused by chance
    • Seen in small populations
Founder Effect

Population Bottleneck

The population almost goes extinct

A few surviving members survive and reproduce

  • A small sample of a population emigrate to a new area
  • Alleles that were uncommon in the parent population become popular
gene flow
Gene Flow



  • Immigration and emigration
  • Increases variation within a population
  • Promotes inbreeding
  • Can cause alleles frequency to change
  • Female is usually choosey
  • Male usually displays traits
types of selection
Types of Selection
  • The best suited individuals survive
  • Derive a situation that could cause each graph.
human evolution
Human Evolution
  • What is a primate (Ape)
    • Manual dexterity
    • Flexible bodies
    • Limber shoulders and hips
    • Large Brain
    • Can solve problems
    • Social
    • Newborns dependent on mother
    • Have fewer offspring
  • Are you an ape?
  • Bipedalism- changing environment
  • Large Brain- evolved after bipedalism