The Theory of Evolution

Jean Baptiste Lamarck ~ 1809 Recognized that species were not constant. Believed species changed over time.

1. The Law of Use and Disuse- States that the more something is used by an organism, the stronger it becomes. & vice versa

2. Inheritance of Acquired Characteristics- Assumes that characteristics acquired through use and disuse could be passed on to offspring.

August Weismann

Disproved Lamarck Cut the tails of 100’s of mice Bred the tailless mice All of the offspring had tails

Charles Darwin ~1800’s

1. Begins a 5 year journey on the HMS Beagle to catalog plant and animal species around the world.

2. Collects evidence for evolution based on:a. Fossil evidence b. Observations of subtle changes in:

• Plants• Insects• Birds (i.e Darwin’s Finches @ Galapagos)

3. 1859 ~ Published landmark book On The Origin of Species.

6 Main Points of Darwin’s Theory

1. Overproduction

2. Competition

3. Variation

4. Adaptation

5. Natural Selection

6. Speciation

Darwin’s Finches An example of speciation from the Galapagos

1. Each species gives birth to more babies than the environment can support

2. Individuals compete for limited resources

3. Phenotypes vary in each population

4. Some variations in the population have advantages over others.

5. Nature causes the weak to die before they reproduce.

6. The changes can be so great to cause new species to arise.

Saddleback Tortoise: Smaller Found on “lower” more

arid islands Food is less available Notch in the shell to

allow better reaching for food

Dome Shelled Tortoise: Larger Found on mountains More rain = more

vegetation Easier habitat for

foraging. No “notch” in shell.

Galapagos Tortoises There are 14 “races!”