Download Theories of evolution notes

What is variation?
Agenda for Wednesday May 18th
1. Variation lab
Test tomorrow
How do we get variation?
Agenda for Thursday May 26th
1. Theories notes
Variation
• What is variation? Examples.
• How do we get variation?
• Can everybody have the same
types of variation? Explain.
• Gene pool – set of genes
available in a population
Jean Baptiste de
Lamarck
• Use and Disuse
• Inheritance of Acquired Characteristics
– Organisms acquire traits and pass these traits to
offspring
Lamarck’s Influence
Incorrect
• Not all traits acquired get passed on
Important
• Introduced change over time
• Realized organisms are changing
Charles Darwin
• Naturalist
• Traveled on the HMS Beagle (1831-1836)
• South America, Galapagos Islands, Australia
• Wrote The Origin of Species
Galapagos Islands
• small group of volcanic islands
• no land mammals or amphibians
The Journey Home
• Characteristics of many plants and animals
vary greatly among the islands
• Hypothesis: Separate species may have
arose from an original ancestor
Finches
• All had differentiated into 14
species
• different beaks specialized for
a particular food source
• Conclusion
– ancestral group of finches
colonized islands
– Absence of competitors
allowed finches to gradually
become specialized
People influenced Darwin
• Charles Lyell
• Malthus
– populations can grow exponentially
– the are limited by war, disease, or resources
• This led to Darwin’s idea that there’s a struggle
for existence
Darwin’s Theory
• Humans can breed for certain traits
– Dogs
– Domestic plants
• Could also happen in nature
– Over time this could produce new species
Darwin’s Theory
• Natural selection – organisms best suited for
the environment reproduce more successfully
– Survival of the fittest
• Over several generations organisms with
favorable traits increase
1. Variation within a population
2. Variations are passed on
3. More offspring are produced than can survive
4. Organisms that survive have favorable variations
(adaptations)
Modification by Natural Selection
• Fitness – genetic contribution to next generation
• Environment “selects” traits
– Favorable traits depend on demands of env’t
Reproduce
more
Greater
fitness
Better
adapted
Summary of Darwin
• Natural Selection – organisms best adapted to
the environment survive and reproduce
• the population is the unit of evolution
– individuals do not evolve during their lifetimes
What is natural selection?
Agenda for Friday May 27th
1. Finish notes
2. Breeding bunnies lab
3. Theories coloring
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• Cheetahs are able to run faster than 60 miles
per hour when chasing prey. How would a
biologist explain how the ability to run fast
evolved in cheetahs, assuming their ancestors
could run only 20 mph?
• A long time ago, some cheetahs were faster than the
others
• The cheetahs that could run faster were able to catch
their prey and were better able to survive
• The slow cheetahs died off, or weren’t able to
reproduce as successfully
• The cheetahs that survived were the ones that could
run faster
How does gene pool relate to
variation?
Agenda for Wednesday May 21st
1. Finish theories notes
How did the heavy coat in polar bears evolve
if their ancestors had thinner coats?
1. A long time ago, some polar bears had
thicker fur than others
2. The thicker coat was favorable
3. The polar bears with thin coats died off.
4. The ones with thicker coats survived and
reproduced.
Peppered Moths
Theory of Evolution
• Evolution – change in the inherited traits of a
population of organisms over time
– NOT new species arising from pre-existing species