Darwin and Evolution

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Evolutionand Darwin
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Evolution

• The processes that have transformed life on earth
  from its earliest forms to the vast diversity
  that characterizes it today.
• A change in the genes!!!!!!!!

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• The one scientist who is most well known for
  evolution is Charles Darwin
• He did not reach this conclusion on his own

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Ideas that helped shape Darwins thinking

• James Hutton Theory of geological change.
• He proposed that the earth is shaped by
  geological forces that took place over extremely
  long periods of time. He estimated the earth to
  be millions of years old, not thousands (as
  previously thought).

• This idea led Darwin to realize that if the earth
  was millions of years old (not thousands), it
  would mean there was enough time for organisms to
  evolve.

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Ideas that helped shape Darwins thinking

• Charles Lyell published Principles of Geology.

• Explained that the processes occurring now have
  shaped earths geological features over long
  periods of time. These processes are still
• changing earth today.
• This idea led Darwin to
• realize that if the earth
• could change then so
• could life

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Ideas that helped shape Darwins thinking

• Jean Baptiste Lamarck (early 1800s) proposed
• The inheritance of acquired characteristics

• He proposed that by using or not using its body
  parts, an individual tends to develop certain
  characteristics, which it passes on to its
  offspring.

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Ideas that helped shape Darwins thinking

• First scientist to propose a mechanism for how
  organism change.
• HE WAS WRONG!!!

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Ideas that helped shape Darwins thinking

• Thomas Malthus Predicted that the human
  population will grow faster than the space and
  food supplies needed to sustain it.
• This same prediction applies to organisms in
  nature as well and leads to competition among them

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Charles Darwin

• With this information in his mind Darwin set sail
  on the H.M.S. Beagle (1831-1836) to survey the
  south seas to collect plants and animals.
• On the Galapagos Islands, Darwin observed species
  that lived nowhere else in the world.

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Charles Darwin

• Even though the islands are fairly close together
  they have different environments. Varying from
  lush jungle to bare volcanic land.

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Charles Darwin

• In these different environments Darwin found
  different types of animals
• Finches were very different on each island
• Tortoises had very different necks on each island

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Charles Darwin

• Charles Darwin is credited with the theory of
  evolution, but scientists knew that organisms
  change over time before Darwin..what Darwin
  really came up with is the mechanism for change
  (HOW organisms changed over time)

Darwins observations on the Galapagos and his
knowledge that things change over time led him to
write a book.
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Charles Darwin

• Wrote in 1859 On the Origin of Species by Means
  of Natural Selection
• Two main points
• 1. Species were not created in their present
  form, but evolved from ancestral species.
• 2. Proposed a mechanism for evolution NATURAL
  SELECTION

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Natural Selection

• Individuals with favorable traits are more likely
  to leave more offspring better suited for their
  environment.

• Example Peppered moth
• Has both dark and light types

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Natural Selection

• Overtime, natural selection results in changes in
  the inherited characteristics of a population.
• These changes increase a species fitness
  (survival rate)

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Natural Selection

• Natural selection is also sometimes called
  survival of the fittest". In this case,
  fittest does not necessarily mean fastest,
  strongest, etc Fittest simply means the
  organism has a trait that helps it survive and
  reproduce (called an adaptation)

• If you are a turtle fittest might mean
  strongest shell
• If you are a chameleon fittest might mean best
  camouflage

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Artificial Selection

• The selective breeding of domesticated plants and
  animals by man.
• nature provides variation, humans select
  variations that are useful.
• Example - a farmer breeds only his best livestock

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Evidence of Evolution

• 1. Fossil Record
• Fossils, and the order in which they appear in
  layers of sedimentary rock, show the history of
  life on earth and how different groups of
  organisms have changed over time

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Evidence of Evolution

• 2. Biogeography Geographical distribution of
  species. Similar animals in different locations
  were the product of different lines of descent

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Evidence of Evolution

• 3. Homologous Structures Structures that are
  similar because of common ancestry.
• e.g. Wing of bat,
• human arm, leg of
• turtle
• Provides strong evidence that all four-limbed
  animals have descended, with modifications, from
  a common ancestor

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Evidence of Evolution

• 3. Homologous Structures.
• Not all homologous structures serve important
  functions. The organs of many animals are so
  reduced in size that they are just vestiges, or
  traces, of homologous organs in other species.
  These vestigial organs are organs that serve no
  useful purpose in an organism
• e.g. pelvic bones in whales, appendix, wisdom
  teeth and coccyx in humans

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Evidence of Evolution

• 4. Comparative embryology
• In their early stages of development, chickens,
  turtles and rats look similar, providing evidence
  that they shared a common ancestry.

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Evidence of Evolution
Evolution can be observed all around us..