1. LaMarck vs. Darwin

2. What is a Theory?
Theory – the most probable explanation for a large set of data based on the best available evidence
Theories are used to make predictions about new data

3. Jean Baptiste LaMarck’s Theory
Believed change occurs over time within a single generation
Inheritance of Acquired Characteristics
acquired changes were passed to offspring
Law of Use and Disuse
If a body part were used, it got stronger
If a body part was not used, it got smaller

5. LaMarck’s Theory of Evolution
Traits acquired during one’s lifetime would be passed to offspring.
Clipped ears of dogs could be passed to offspring!

6. LaMarck’s Mistake
Reminder from genetics – Traits are passed through genes.
Lamarck did not know how traits were inherited.
Genes are not changed by activities in life
Genes are changed through DNA mutations that are passed onto offspring

7. Voyage of the Beagle Charles Darwin
HMS Beagle, 1831 for 5 year voyage around world
Avid collector of flora & fauna
Astounded by variety of life

8. Voyage of the Beagle
During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time

9. Darwin’s Belief’s Survival of the Fittest OR Natural Selection
Food and resources are limited
There are too many organisms, so they will compete to survive.
Not all offspring will survive; only those best suited to environment survive.

10. Darwin’s Giraffes Giraffes with a variety of neck lengths existed.
The giraffes had to compete for food.
Short necks could not reach upper branches, limiting their food supply and causing them to die
Long neck giraffes survived because they were able to reach the food
Long neck giraffes reproduce and pass on genes.

12. So What is a Good Definition of Evolution?
Evolution is the slow, gradual change in a population of organisms over many generations of time
The change of a genetic population through successive generations
The change of a species over time.

13. Natural Selection Selective pressure can occur from several factors:
Resource limitation
Predation
Industry (Environment)
Social influence (Society)

14. Classic Example
Peppered moths