1. Evolution

2. Populations evolve, Individuals DO NOT evolve!
Evolution is . . .
A change in a kind of organism over time
A process by which modern organisms have descended from ancient organisms
Populations evolve, Individuals DO NOT evolve!

3. Charles Darwin
Born on February 12, 1809 in England
Proposed that evolution occurs via natural selection.

4. Voyage of the Beagle (1831-1836)
Darwin sailed around the world
Made many observations and collected lots of evidence about how life is changing

5. Galapagos Islands

6. Galapagos Islands
Darwin's finches share similar size, coloration, and habits.
One difference among finches was beak size
Key Observation: organisms are remarkably suited to their environment

7. Examples of some of the Finch Species

8. Common Thought in Darwin’s Time
Earth is only a few thousand years old
Neither planet nor living things have changed

9. Hutton & Lyell (Discoveries ~1785 - 1833)
Earth is much older than only a few thousand years
Cited formation of rock layers as evidence
Rattlesnake Canyon in Colorado

10. Malthus (1798)
Reasoned that if the human population continues to grow unchecked, sooner or later there would be insufficient living space and food for everyone
Forces working against growth = war + famine + disease

12. Lamarck (1809) Tendency towards perfection Use & disuse
Inheritance of acquired traits

13. Darwin Publishes His Work (1858)
“It was evident that such facts as these Could be explained on the supposition that species gradually became modified, and the subject haunted me.”

14. Artificial Selection
Members of each species vary from one another
Variable traits are passed from parent to offspring
Humans select organisms with variations that they find to be most useful

16. The Struggle for Existence
Organisms produce many offspring, few survive
Members of each species compete regularly for food, living space, and other necessities

17. Natural Selection / Survival of the Fittest
Fitness = the ability of an individual to survive and reproduce in its specific environment

18. Fitness results from adaptations
Adaptation = any inherited characteristic that increases an organisms chance for survival

19. Natural Selection / Survival of the Fittest
Individuals with low fitness (those not well suited for environment) either die or leave few offspring

20. Evidence of Evolution - - The Fossil Record
Countless species have come into being, lived for a long time, and then vanished
Fossils document stages in evolution of modern species from organisms that are now extinct

21. Archaeopteryx – thought to be first bird, wings are very primitive.

22. Homologous Body Structures
Structures that have different mature forms in different organisms but develop from the same embryonic tissue

23. Alligator
Mammal
Turtle
Bird

24. Why do vestigial organs remain?
Organ that serves no useful function in an organism
Ex: tailbone in humans, legs in skinks
Why do vestigial organs remain?

25. Similarities in Embryology
The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates

27. Summary of Darwin’s Theory
Species alive today are descended with modification from ancestral species that lived in the distant past. This process, by which diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life.