Transcript Natural Selection Examples

Natural Selection
Your Definition
• How would you describe the
mechanism of natural selection?
Natural Selection...
• is the primary mechanism of
evolutionary change
• changes the genetic make-up of a
population
• is the “survival of the fittest”
• Why is “reproduction of the
fittest” a better description than
“survival of the fittest?”
– Fitness = leave the most descendants
Necessary conditions for
natural selection
1. Genetic variation in a population
2. More offspring produced than can be supported
by environment
3. Organisms compete and resources limited
4. Differential reproduction - individuals most suited
to environment reproduce
– “reproduction of the fittest”
5. Over time, beneficial gene becomes more
common and population changes
Acquired Characteristics vs.
Natural Selection
• Variations are
purposeful
• Variations are
random
• Variations are the
result of an
organism striving to
be better
• Variations due to
genetic mutation
Natural Selection Examples
Using the variation in snail shells (as seen in the
picture), make up a scenario in which natural
selection might occur in this snail population.
Biogeography
•
http://www.ucmp.berkeley.edu/education/e
xplorations/tours/stories/middle/G8.html
Biogeography
• Write down one observation you
can make about how the yellow
line moves.
• What is the explanation (inference)
for why the same type of tree is
found in many parts of the world?
Common Ancestor
Geographic Isolation
A Variety of Beaks
Reproductive Isolation
Divergent Evolution
Explain the following
statement...
• Speciation occurs through
divergent evolution.
Extinction
• Extinction is the ultimate fate of all
species
• 99.9% of all the species that have ever
existed are now extinct
Factors affecting speciation
and extinction
• large-scale movement of the continents
• gradual climate changes
• rapid climate changes
Speciation - Extinction =
Biodiversity
Variations in Guppies
Selecting a Variety of
Peppered Moths