1. Darwin’s Theory of Evolution
Organisms Change OverTime

2. Common Descent with Modification
Darwin proposed that organisms descended from common ancestors
Idea that organisms change with time, diverging from a common form
Caused evolution of new species

3. Natural Selection Driving force for evolution
During the struggle for resources, strongest survive & reproduce
Idea that at least some of the differences between individuals, which impact their survival and fertility, are inheritable .

4. Darwin Presents His Case
Origin of Species
Darwin Presents His Case

5. Publication of “On The Origin of Species”
Upon His Return To England, Darwin Developed His Observations Into The Theory of Evolution
But He Did Not Publish For 25 Years –
Why?

6. Publication of “On The Origin of Species”
Darwin Knew That His Theory Would Be Extremely Controversial And Would Be Attacked
His Theory Challenged Established Religious & Scientific Beliefs, Particularly About The Creation Of Man

7. Publication of “On The Origin of Species”
He Refused To Publish Until He Received An Essay From Alfred Wallace
Fellow Naturalist
Independently Developed The Same Theory
After 25 Years, Someone Else Had Come To The Same Conclusions From Their Observations Of Nature

8. Wallace’s Contribution
Alfred Russel Wallace Independently came to same Conclusion as Darwin that species changed over time because of their struggle for existence
When Darwin read Wallace’s essay, he knew he had to publish his findings

9. Natural Variation and Artificial Selection
Abandoned The Idea That Species Were Perfect & Unchanging
Observed Significant Variation in All Species Observed
Observed Farmers Use Variation To Improve Crops & Livestock
Called Selective Breeding

10. Natural Variation and Artificial Selection
Differences Among Individuals Of A Species
Artificial Selection
Selective Breeding To Enhance Desired Traits Among Stock or Crops

11. Natural Variation and Artificial Selection
Key Concept:
In Artificial Selection, Nature Provided The Variation Among Different Organisms, And Humans Selected Those Variations That They Found Useful

13. Concepts and Controversy
Origin of Species
Concepts and Controversy

14. Evolution By Natural Selection Concepts
The Struggle for Existence (compete for food, mates, space, water, etc.)
Survival of the Fittest (strongest able to survive and reproduce)
Descent with Modification (new species arise from common ancestor replacing less fit species)

15. Survival of the Fittest
Fitness
Ability of an Individual To Survive & Reproduce
Adaptation
Inherited Characteristic That Increases an Organisms Chance for Survival

16. Survival of the Fittest
Adaptations Can Be:
Physical
Speed, Camouflage, Claws, Quills, etc.
Behavioral
Solitary, Herds, Packs, Activity, etc.

17. Survival of the Fittest
Fitness Is Central To The Process Of Evolution
Individuals With Low Fitness
Die
Produce Few Offspring
Survival of the Fittest
AKA Natural Selection

18. Survival of the Fittest
Key Concept
Over Time, Natural Selection Results In Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment

19. Natural Selection Cannot Be Seen Directly
It Can Only Be Observed As Changes In A Population Over Many Successive Generations
Radiation
Fossil Record

20. Descent With Modification
Takes Place Over Long Periods of Time
Natural Selection Can Be Observed As Changes In
Body Structures
Ecological Niches
Habitats

21. Descent With Modification
Species Today Look Different From Their Ancestors
Each Living Species Has
Descended
With Changes
From Other Species
Over Time

22. Descent With Modification

23. Descent With Modification
Implies
All Living Organisms Are Related
Single Tree of Life
DNA, Body Structures, Energy Sources
Common Descent
All Species, Living & Extinct, Were Derived From Common Ancestors

24. Major Problem in Darwin’s Theory
No mechanism to explain natural selection
How could favorable variations be transmitted to later generations?
With the rediscovery of Mendel’s work in the first half of the 20th century, the missing link in evolutionary theory was found .

25. Opposition to Evolution
The upheaval surrounding evolution began with Darwin’s publication of On the Origin of Species By Means of Natural Selection
The debate continues nearly 150 years later