1. Aim: What are the most important theories on how organisms evolved?
Important Evolutionary Theories!
Aim: What are the most important theories on how organisms evolved?

2. Time Frame for Evolution
Evolution does not progress in any set direction!
Punctuated Equilibrium:
Gradualism:
- periods of stability
interrupted by brief
periods of change
- slow, continuous
change over time

3. CLADOGRAM: An evolutionary tree of life enabling us to compare relatedness through ancestry
EXTINCT:
Ends abruptly B
Which 2 are most closely related? Why?
Which letter represents the common ancestor of Birds and Amphibians? C D

4. Inherited Characteristics Acquired Charactersitics
Make a list of your…
Inherited Characteristics
Acquired Charactersitics
blue eyes
Light skin
tall
Good public speaker
Play the violin
Funny
Dancing skills

5. Lamarck’s Theory of Evolution
Individual organisms develop new structures over the course of their lifetime because they need them in their environment
Ex. Giraffes developed longer necks because they had to stretch to reach the trees
Offspring will inherit this ACQUIRED characteristic
Ex. Baby Giraffes are born
with long necks b/c parents grew longer muscles

6. Weismann (disproved Lamarck)
Experiment:
cut off tails from mice
bred the tail-less mice
offspring had tails!
• Conclusion: acquired traits are NOT inherited by the offspring, thereby proving Lamarck WRONG!

7. That would be as if… You work out… Become very muscular…
And have a built baby!

8. Theory of Natural Selection (Charles Darwin)
Introduced the idea that the environment / nature selects an organisms traits
“Survival of the fittest”
Organisms with adaptations better suited (favorable) for their environment will survive to reproduce more successfully than those without