1. 15.2 – Ideas That Shaped Darwin’s Thinking

2. Interest Grabber My, How You’ve Changed!
Section 15-2
My, How You’ve Changed!
Prior to the 1800s, life scientists knew that living things changed over generations. They just didn’t know how these changes were brought about.
1. Divide a sheet of paper into two columns and title the first one Inherited Characteristics. Title the second column Acquired Characteristics. In the first column, list the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair.
2. In the second column, list your acquired characteristics. For example, you may have learned how to play a musical instrument.
3. Which of the items in your lists do you think you might pass on to your children? Explain your answer.

3. Darwin’s Ideas
Darwin greatly changed the thinking of many scientists, but also many did not believe him
Most Europeans at the time believed Earth was only created a few thousands of years before present time
They believed everything was created the way it was and never changed
By the time Darwin set sail there was a rich fossil record challenging this idea

4. Lamarck’s Theory of Evolution
One of first scientists to recognize things have changed over time
He also recognized organisms were adapted to their environment
He proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime
And then be inherited

5. Lamarck’s Examples

6. Lamarck’s Theory of Evolution
Section 15-2
Fiddler Crab example
2. Use and disuse
Waving to attract mates
Tendency towards perfection
Changing to live more successfully
3. Inheritance of acquired characteristics

7. Objective: Summarize Lamarck’s theory of evolution through inheritance of acquired characteristics
Jean Baptiste Lamarck ( )
Assumed that body parts used more frequently become stronger and more developed
Assumed acquired characteristics were inheritable
Predictions based on a hypothesis can be stated in an if then format
If dog ears cropped, then offspring will be cropped.
Not supported
If parents weight lift, then children will have well-developed muscles.

8. Lamarck’s Theory His theory is incorrect in several ways
He didn’t know how traits are inherited
He did not know that an organism’s behavior has no effect on its inheritable characteristics
He was one of the first to develop the Theory of Evolution and realize animals adapt to their environment

9. Population Growth
In 1798, Thomas Malthus saw babies were being born faster then people were dying
He reasoned if that continues to happen the time might come when there is insufficient land and food on Earth to support the population size
Does this apply to all living organisms?
Darwin realized this reasoning applied even more strongly to plants and animals than it did to humans.
Humans produce far fewer offspring
The overwhelming majority of a species’ offspring die