Darwin and the development of the theory

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The Theory of Evolution
Charles Darwin and the Theory of Evolution

• Darwin and the development of the theory

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What is a SPECIES?

• Group of similar organisms
• Structurally
• biochemically
• Can interbreed successfully in nature
• Offspring are healthy
• Offspring are fertile (can reproduce)

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These organisms are not new speciesWhy?

• Mule

• Liger

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Variation

• Variation differences between individual
  members of a population
• Members of a species are very similar, but
  differences can be observed, or not, make each
  individual unique.
• May be caused by mutations

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Mutations

• Changes in DNA base sequences
• Most are either neutral or harmful
• Those that allow the organism to survive better
  in a particular environment are good and are more
  likely to be passed on to future generations.

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Most variations are not caused by mutations

• Sexual reproduction combines genes from different
  parents
• Crossing over during meiosis can produce
  variations

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Adaptation

• An inherited trait that increases the
  populations chances of survival and reproduction
  in a particular environment.
• Allows organisms to fit best into a particular
  niche (habitat and role)

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Biodiversity

• The variety and abundance of species that makes
  up a biological community.
• Pine Barrens forests have little biodiversity a
  limited number of species can survive there.
• Tropical rain forests have great biodiversity
  many species in a concentrated area.

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Organisms have changed over time to produce so
many different forms of life
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Theories accepted before Darwin

• 1769 Bonnet theorized that fossils were from
  animals/plants that lived before catastrophes
  that made them extinct.

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Jean Baptiste Lamarck

• Use and disuse
• Inheritance of acquired characteristics

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Darwin and his theory

• Charles Darwin lived
• in early-mid 1800s.
• Went on voyage around the world as the ships
  naturalist collected specimens of plants and
  animals during the 5year-journey.

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Darwins Voyage
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Galapagos Islands
Darwins route
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Darwin Returned Home to Think!

• These influenced his development of the theory
• Evidence that the 13 different species of finches
  found in the Galapagos Islands were the
  descendents of one species.
• HERE ARE JUST A
• FEW BEAK TYPES

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• Artificial selection farm animals and
  plants

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• Population control population limited by
  resources and nature controls it by killing off
  some members during natural disasters, illness
  (epidemics), blights in plants, etc.
• Geologic evidence
• of slow changes

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Darwins Theory of Evolution by Natural Selection

• There is variation within a population
• Some variations are good (helpful)
• Not all young produced in a generation can
  survive
• This leads to a struggle for existence.
• Survival of the fittest.
• Those that survive and reproduce are those with
  the good variations.

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Evidence supporting Evolution

• Fossils remains of plants or animals that lived
  before can show structures

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Homologous Structures similar in structure, but
have different functions
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Vestigial Structures

• Inherited
• But, reduced in size and often not used.
• Examples
• Snake legs (theyre so reduced in size that they
  are not apparent).
• Human appendix no function, except can cause
  problems.
• Human coccyx tail bone.

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Analogous Structures

• Similar in function, but very different in
  structure indicate organisms are not closely
  related

Insect wings Bat wing Bird wing
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Embryological Evidence

• If organisms have similar embryos, they are more
  closely related than those with less similar
  embryos

Sea lamprEy pond turtle chicken
cat human
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Origin of Species

• Speciation evolution of one or more species
  from a single ancestor species. can be from
• isolation usually because of a geographic
  barrier such as a canyon, mountain, or island

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Divergent Evolution

• Isolated populations of a species evolve
  independently of each other.
• Ex polar bears and brown bears

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Convergent Evolution

• Natural Selection produces analagous (similar)
  adaptations in different organisms in response to
  similar environments
• African Serval cat south american maned wolf
• See text p 242
• These animals have similar ears, legs, acute
  hearing, habitat, and Occupy similar niches

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Coevolution

• Species that interact closely often adapt to one
  another

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Adaptive Radiation

• Many different species evolve from one ancestral
  species each new species has a different niche

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Evolution Observed Peppered Moths
Less pollution
More pollution
Light moths
Dark moths
Light tree

• Dark tree

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The End