Evolution

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Evolution Ecology
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DO NOW Wednesday November 11, 2009

• Describe where you are on the spectrum of beliefs
  and explain why.

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• Origin of Life
• Introduction ?
• Prior to the seventeenth century, scientists
  believed in a process called spontaneous
  generation, or the idea that living organisms
  could spontaneously arise from nonliving things.
• Why?
• Maggots appeared on rotting meat
  
• Fish lived in ponds that were dry the year before

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• Origin of Life
• In an attempt to learn more about spontaneous
  generation, scientists designed controlled
  experiments.
• BUTthese experiments actually disproved
  spontaneous generation and proved a theory called
  biogenesis, or the idea that all living things
  arise from other living things.

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• Origin of Life
• Experiments Supporting Biogenesis ?
• 1. Redis Experiment
• 2. Spallanzanis Experiment
• 3. Pasteurs Experiment

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• Origin of Life
• Soall living things must come from other living
  things. But, where did the first living things
  come from?
• 1. The Miller-Urey
  
  Experiment ?

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• Earths History
• A. Introduction ?
• Scientists estimate that the Earth is more than
  4 billion old. How did they arrive at this
  number?
• B. Relative Dating ? Observing layers of rock
  in order to determine relative age
  (stratification).

Ex Which rock layer is the oldest?
If fossils are found in these layers, the
approximate age can be determined.
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• Earths History
• C. Absolute Dating ? Determining an exact age
  through Radioactive Dating.
• 1. Certain moleculesthrough collisions in the
  atmospherecan become unstable, or
  radioactive.
• 2. Lets look at carbon, for example
• Carbon-12 (normal, 6 protons/6
  neutrons)
• Carbon-14 (radioactive, 6 protons/8
  neutrons)
• (These two molecules are considered isotopes, or
  molecules with the same number of protons but a
  different number of neutrons)

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1. Through photosynthesis, plants take in carbon (a
   constant ratio of C-12 to C-14). So, anything
   that eats plants also consumes carbon.

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1. When an organism dies, no more carbon is
   consumed.
2. Over time, the amount of C-12 stays constant.
   C-14 begins to decay.

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• By comparing the ratio of C-12 to C-14, the
  approximate age of a fossil can be determined.
• Half-life ? the amount of time required for half
  of a material to decay. The half-life of carbon
  is 5,730 years.
• Example Assume, for simplicitys sake, that
  C-12 and C-14 are found in a 11 ratio (instead
  of 11,000,000,000,000). A paleontologist finds a
  fossil containing 80g of C-12 and 40g of C-14.
  Since there were originally equal amounts of C-12
  and C-14
• What percent of the C-14 sample has decayed?
• So, what is the age of the sample?

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• III. The Fossil Record
• Fossils ?
• What?

The remains or traces of a once-living organism.
Formed by hard body parts like shell, bone,
teeth, stems.
Most often found in sedimentary rock (sometimes
metamorphic).
2. Where?
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• III. The Fossil Record
• Fossils ?
• 3. How?

Mold ? An imprint in rock in the shape of an
organism.
(Ex the mold made for
braces) Cast ? A mold is filled with minerals
leaving a rock-like model.
(Ex pouring plaster
into a footprint) Others ? Preservation (ice,
amber, tar) Hard minerals replace soft
tissue (petrified wood) Living Fossils ? The
coelocanth, a deep water fish with fin-like
legs The fossil record shows that the complexity
of life has increased over time