Docstoc

evolution

Document Sample
evolution Powered By Docstoc
					Evolution Notes
  Biology 102A
    Fall 2008
• Darwin explained the
  theory of evolution by
  Natural Selection.
• “Survival of the Fittest”
  means organisms that
  adapt to their
  environment survive,
  while organisms that do
  not adapt disappear.
• Natural selection leads
  to adaptations within a
  population.
                 Types of Evolution
•   Microevolution- the change of allele frequencies
    within a population

•   Macroevolution- large-scale evolutionary changes
    : 5 patterns
    l. Mass extinctions
    2. Adaptive Radiation
    3. Convergent Evolution
    4. Coevolution
    5. Punctuated Equilibrium
             Mass extinctions
• More than 99% of all species that ever
  lived are now extinct
• Mass extinctions wiped out food webs
  & ecosystems
• Example: Dinosaurs- asteroid but
  could have been many factors
  (volcanoes & continents drifting)
         Adaptive Radiation
• A species or group of species evolves into
  many new species
              Convergent Evolution
• Unrelated organisms come to resemble one another



      bird




       fish




          mammal
                  Coevolution
• 2 species evolve in response to changes in each
  other over time
                       Central American Swollen-Thorn Acacias

                   Acacia ants and acacia trees
                       Acacias are small, Central American trees in the
                       Leguminosae. They have large, hollow thorns. The
                       acacia ants live in the thorns. On the tips of its
                       leaflets, the plant makes a substance used by the ants
                       as food. The ants defend the tree from herbivores by
                       attacking/stinging any animal that even accidentally
                       brushes up against the plant. The ants also prune off
                       seedlings of any other plants that sprout under
                       “their” tree
          Punctuated Equilibrium
• Rapid evolution after long periods of equilibrium
  (balance)
• Why? Migration, mass extinctions, isolation
          Evidence for Evolution
The fossil record gave
  us:


1. Descent with
   modification

2. Homologous
   Structures

3. Transitional
   Fossils
        Descent with Modification
• All living organisms are related to one another-
  common descent
• Speciation-new species can arise
       Homologous Structures
• structures in different species that may
  perform different functions but are similar
  in structure because of their common
  ancestry
• Examples: bat wing,
whale flipper, cat claw,
Human hand
Vestigial Organs

– structures of no
  apparent function to
  an organism; leftover
  from ancestry
– Examples: snakes
  have leg & pelvis
  bones; whale rear
  limbs
         Examples of Evolution
• Antibiotic Resistance: natural
  selection has occurred within
  populations of bacteria
• Mutations cause bacteria to change
  their structure…antibiotics cannot
  bind to cell surface
• Acquiring new genes…bacteria
  have new enzymes that can
  deactivate or destroy antibiotic
• Ex:Tuberculosis bacteria
         Examples of Evolution
• Darwin’s Finches: Natural selection has
  occurred in beak size
          Examples of Evolution
• Speciation: begins as a population adapts to its
  environment.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:10
posted:1/22/2012
language:English
pages:15