Transcript Natural selection is not intentional!

Natural Selection
How Changes in Organisms Can Be Explained
What did
Darwin see?
What did Darwin see?
• The earth has been changing over time
• Living things have been changing over
time
• Traits of organisms differed between
islands
• Organisms had traits to fit environment
What did Darwin see?
Finches in the Galapagos
•Finch species existed on
mainland of South America
•Some relocated to Galapagos
Islands 900 km away and
became their own population
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•Birds living in these new
environments changed over time
to create noticeable differences
•Colors
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•Diets
•Body structures (beaks)
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What did Darwin see?
Darwin’s Conclusions
• 1836 – 1858 (22 years)
– Darwin studies observations
– Writes a manuscript and puts in on a shelf.
• 1858 – Alfred Russel Wallace
– Naturalist in studying in Malaysia
– Reached same conclusion (evolution) as
Darwin
• 1859 - Darwin finally published his ideas,
The Origin of the Species
Darwin’s Conclusions
• Descent with Modification
– Organisms split off from common ancestor and
undergo changes (modifications) to fit their
environmental conditions
• Natural Selection
– The mechanism by which living things change
– Individuals with traits that make them better
able to survive in their environments will leave
more offspring than others
What is Evolution?
• Process by which
today’s organisms
have descended
from ancient
organisms
• Change over time
What is Natural Selection?
1. Individuals within a species vary.
2. These variations are inherited by their offspring.
3. Organisms produce more offspring than can possibly
survive.
4. Offspring with the most favorable variations will
survive and reproduce. They are naturally selected.
5. Over time, offspring with the most favorable variation
make up most of the population and may look entirely
different from their ancestors.
Results of Natural Selection
Organisms with highest “fitness” will survive,
reproduce, and pass on genes
• (remember Kerosene Karl)
– Fitness is an organism’s ability to survive and
reproduce in its environment
Variation in fitness and reproduction of organisms leads
to genetic and physical changes in populations
Fit and Stinky!!!
Results of Natural Selection
• Evolution by natural selection happens
over millions of years
• Natural selection is not intentional!
How Many Species
of Dogs Exist?
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Artificial Selection
Dog Breeding:
• Humans have been selecting for
desired traits
• We hundreds of varieties of dogs!
• Only been happening for a few
hundred years
Natural Selection
has been happening for billions of years!
Think of all the changes that have accumulated…