How can fossils show us what happened in the past?

Agenda for Thursday May 15th 1. Fossil lab

Timeline due tomorrow

What is variation?

Agenda for Friday Feb 13th 1. Variation lab

How do we get variation?

Agenda for Wednesday Feb 18th 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

• Back in England he looked at his findings– Tortoises and Finches

Animals

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

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

How does gene pool relate to variation?

Agenda for Wednesday May 21st 1. Finish theories notes

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.

Peppered Moths