CHAPTER 15 NOTES EVOLUTION

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CHAPTER 15 NOTES EVOLUTION
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EVOLUTION change over time
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CHARLES DARWIN

• Contributed more to our understanding of
  evolution than anyone

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• Journeyed around the world on the HMS Beagle and
  made observations and collected evidence
• Collected fossils (preserved remains of ancient
  organisms)
• The islands that influenced Darwin the most were
  the Galapagos Islands (a group of islands with
  very different climates)

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Darwin on HMS Beagle A 5 year trip
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Darwins Observations

• Darwin was intrigued by the fact that so many
  plants and animals seemed remarkably well suited
  to whatever environment they inhabited.
• He was also puzzled by where different species
  lived and did not live.
• He soon realized that living animals represented
  just part of the puzzle posed by the natural
  world.

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The Galapagos Archipelago
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The Galapagos Iguanas
Land Iguana
Marine Iguana
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The Galapagos Tortoises
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• Darwin learned that the giant tortoises varied in
  predictable ways from one island to another.
• The shape of a tortoise's shell could be used to
  identify which island a particular tortoise
  inhabited.
• Darwin later admitted in his notes that he did
  not for some time pay sufficient attention to
  this statement.

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The Galapagos Tortoises
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• One tortoise from an island with sparse
  vegetation has a long neck and shell that is
  curved to reach.
• Another tortoise has a dome-shaped shell and a
  shorter neck because vegetation on this island is
  more abundant and easier to reach.
• Another tortoise has a shell that is intermediate
  between these two forms.

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The Galapagos Finches
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The Galapagos Finches
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Darwin Gathers More Evidence

• English animal breeders were selectively breeding
  birds to get large, colorful feathers for ladies
  hats.
• This was a type of artificial selection because
  the breeders were controlling which traits were
  crossed.
• Darwin wondered if some force in nature also
  selected which organisms would survive.

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Results of Artificial Selection
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Other Scientists that influenced Darwin

• 1. Hutton Lyell studied geological change to
  show that the Earth changes over long periods of
  time

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• 2. Malthus reasoned that if the human population
  continued to grow unchecked, sooner or later
  there would be insufficient living space and food
  for everyone (war, famine and disease help keep
  this growth in check)

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• 3. Lamarck was the first scientist to recognize
  that living things change over time

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Lamarcks ideas

• 1. Organisms constantly strive to improve
  themselves (tendency toward perfection)
• 2. Most-used body structures develop, but unused
  ones waste away (use and disuse)

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• 3. Once a structure is modified by use or disuse,
  the modification is inherited by the organisms
  offspring (inheritance of acquired
  characteristics)
• A giraffes neck gets long because he reaches.
  His offspring inherit the long necks.
• ALL OF THESE WERE PROVEN WRONG, but Lamarck paved
  the way for the work of later biologists.

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Darwins Grand Idea

• Darwin spent over 20 years gathering facts that
  might have some bearing on how species
  originated.
• Putting all of his amassed data together, Darwin
  developed his grand idea.
• Darwin didnt go public with his ideas because
  the dominant philosophy of his day placed the
  most value on gathering facts, not on
  hypothesizing.

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Darwins Dilemma

• On June 18, 1858, Darwin received a letter from a
  fellow scientist, Alfred Russell Wallace.
• In the letter was an abstract of a theory of
  evolution that Wallace was about to publish.
• He was asking Darwin for a peer review of his
  theory before submitting it for publication.

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Alfred Russell Wallace (1823-1913)
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Darwin Wallace

• Wallaces theory was exactly the same as
  Darwins!
• Darwin was ready to concede, but mutual friends
  encouraged Darwin Wallace to allow their theory
  to be jointly presented.
• Thus, on July 1, 1858, their theory was jointly
  presented to the Linnaean Society of London.

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Charles Robert Darwin in 1859
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Darwin Gets Credit

• Darwin is given primary credit for the theory of
  evolution by natural selection because (1) he
  had collected more evidence than Wallace and (2)
  he had written, but not published, a general
  outline and an essay on evolution at an earlier
  date (1844).
• Although controversial, many prominent scientists
  supported Darwin Wallace.

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Darwins Book

• The following year, 1859, Darwin published his
  full theory with evidence.
• The title was On The Origin of Species by Means
  of Natural Selection. All 1,250 copies of the
  first printing were sold on the first day!

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Survival of the Fittest

• In 1866, the English philosopher Herbert Spencer,
  in an attempt to explain what Darwin meant by the
  struggle of organisms in nature, coined the
  phrase survival of the fittest.
• The phrase is often attributed to Darwin but it
  does not appear in any of his writings.

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• Definitions
• Variation differences between individual
  members of a population (ex. Color of fur, shape
  of teeth)
• Adaptation an inherited characteristic that
  increases an organisms chance of survival

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Darwins Theory of Natural Selection

• 1. There is variation within a population.

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• 2.  Some variations are favorable.

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• 3.  Not all young produced in each generation can
  survive. (struggle for existence)

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• 4.  Individuals that survive and reproduce are
  those with favorable variations (survival of the
  fittest)

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• 5. All species have common ancestors. (Descent
  with modification)

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EVIDENCE OF EVOLUTION

• According to evolutionary theory, all life
  originated from a common ancestor.
• Common descent the theory that all species were
  derived from common ancestors

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WAYS TO DETERMINE HOW RELATED ORGANISMS ARE
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1. Fossils

• The fossil record reveals changes in populations
  over time and supports the theory of evolution.
• Scientists can calculate a fossils age by using
  radioactive dating or relative dating (we will
  discuss this later)

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• The fossil record is incomplete, but it still
  shows us relationships between species and how
  their structures have changed over time.
• Fossils are mostly found in sedimentary rock.

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2. Homologous Structures

• Homologous structures structures that have
  different mature forms, but develop from the same
  tissues
• Ex. Arms, wings, and flippers are all
  constructed from the same basic bones

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Homologous Structures
Flying
Swimming
Running
Grasping
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• 3. Vestigial structures structures reduced in
  size and often unused
• Ex. Leg/hip bones in pythons and whales or
  appendix in humans

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 4.Embryology Biochemistry

• Embryology compare how embryos of different
  species look during certain stages of development

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• Biochemistry compares the biochemicals that
  make up our body (amino acid)

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The Fact of Evolution

• Darwinism is not just a theory as many believe.
  
• Darwins conclusion that species change over time
  is a scientific, proven fact.
• The mechanism suggested by Darwin for that
  change, natural selection, is a theory.

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