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How can fossils show us what happened in the past?
Agenda for Thursday May 15th 1. Fossil lab
Timeline due tomorrow
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
• Back in England he looked at his findings– Tortoises and Finches
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
Modification by Natural Selection• Fitness – genetic contribution to next generation• Environment “selects” traits
– Favorable traits depend on demands of env’t
Greater fitness
Better adapted
Reproduce more
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
Theory of Evolution• Evolution – change in the inherited traits of a
population of organisms over time– NOT new species arising from pre-existing species
• Part but not all of evolution
What is natural selection?
Agenda for Thursday Feb 19th 1. Peppered moth lab2. Finish theories coloring
• 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
I can describe why the majority of the variation in a population is
seen as a bell-shaped curve.
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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 favorable3. The polar bears with thin coats died off.4. The ones with thicker coats survived and
reproduced.
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