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					Chapter 6

Adaptations Over Time
Ch 6.1 - Evolution

 A. Evolution – changes in inherited
   characteristics of a species over time

  1. A species is a group of organisms that
  share similar characteristics and can
  produce fertile offspring
B. Early Models of Evolution

 1. Acquired characteristics – proposed by
 Jean Baptiste de Lamarck

 2. Suggested that traits developed during
 an organisms life time could be inherited
 by future offspring

 3. This theory was not supported by
C. Darwin’s Model of Evolution

1. Charles Darwin observed that species of
  finches on the Galapagos Islands looked
  similar to mainland finch species
2. Darwin hypothesized that plants and
  animals on the Galapagos Islands off the
  coast of South America originally came
  from Central and South America
3. He reasoned that members of a
population best able to survive and
reproduce will pass their traits to the next

4. Over time these differences result in
new species
5. Darwin’s hypothesis became known as
  the theory of evolution by natural

    “ Organisms with traits best suited to
 their environment will more likely survive
 and reproduce.”
D. Variation – an inherited trait that makes
 an individual different from other
 members of its species

 1. An adaptation is a variation that makes
 an individual better suited to its
2. Many environmental factors can cause
  changes in the sources of genes

 3. Geographic isolation can make 2
 populations so different that they can
 become different species
E. Speed of Evolution

 1. Gradualism – describes evolution as a
 slow, ongoing process

 2. Punctuated Equilibrium – model says
 gene mutation can result in a new
 species in a relatively short time
Ch 6.2 – Clues About Evolution

 A. Direct Evidence of Evolution

   1. Fossils – found in sedimentary rock
   show that living things evolved

   2. Bacteria – development of antibiotic
   resistance in bacteria
B. Fossils age can be determined by 2

  1. Relative Dating – looks at fossil
     location in particular layer of rock;
     older rock layers are under newer
     rock layers
2. Radiometric & Carbon Dating –
  compares the amount of radioactive
  element or carbon with the amount that
  does not contain these
C. Fossil records have gaps

 1. Incomplete rock record b/c most
 organisms do not become fossils

 2. Enough fossils have been discovered
 for scientists to conclude that complex
 organisms appeared after simpler ones

 3. Most organisms that have ever existed
 are now extinct
D. Indirect Evidence of Evolution

 1. Embryology – the study of embryos
 and their development shows similarities
 among all vertebrate species
2. Homologous body parts – can indicate
  that 2 or more species share a common
3. Vestigial Structures – structures that do
  not seem to have a function but might
  have once functioned in an ancestor
4. DNA – can provide evidence about how
  closely related organisms are
Ch 6.3 – Evolution of Primates
A. Primates – group of mammals with
  opposable thumbs, binocular vision and
  flexible shoulders
Lemurs, Tarsiers, Monkeys, Apes & Humans
1. Hominids - appeared about 4-6 million
  years ago and had larger brains than
2. Fossils such as Australopithicus point to
  Africa as the origin of hominids
3. Homo habilis and Homo erectus – are
  thought to be early human ancestors
B. Homo sapiens – “Wise Human” began
  evolving about 400,000 years ago

 1. Neanderthals – had short, heavy
 bodies with thick bones, small chins and
 heavy brow ridges

 a) Disappeared about 30,000 years ago

 b) Not thought to be a direct ancestor to
 modern day humans
2. Cro-Magnon humans – fossils date from
  around 10,000-40,000 years ago

 a) Are thought to be a direct ancestor to
 early Homo sapiens

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