1. Evolution and Natural Selection

2. Theory of Evolution Evolution = Change in a population over time
Theories = explanation of a natural phenomenon
Theories can be either supported or disproved but never proven
What phenomenon does evolution explain?
Every organism is different (diversity)
All organisms have things in common (Genetic code)

3. Theory of Evolution 2 Views of evolution:
Microevolution = Small changes over short periods of time
Supports improvements in existing species
Macroevolution = small changes accumulating over long periods of time resulting in major changes
Supports the formation of new species

4. Three Types of Evolution
Divergent – similar Organisms become increasingly different because of different types of environments (ex. Darwin’s Finches)

6. Three Types of Evolution
Convergent – different organisms become increasingly similar because of similar types of environments (ex. Sharks and dolphins)

8. Three Types of Evolution
Coevolution (Parallel) - two non-related species change because of their close interactions (ex. Predator/prey or plant/pollinator)

9. Cladogram
Cladogram = tree showing evolutionary relationships based on similar characteristics
Shows divergent evolution
What trait separates rodents from birds?
Which two species are more related, crocodiles and birds or crocodiles and rabbits?

10. Natural Selection
Natural Selection = organisms adapt to their environment (“survival of the fittest”)

11. History of Natural Selection Theory
Jean-Baptiste Lamarck (1700s) = first person to state organisms change over time and new organisms are modified from descendants of older organisms
Theory of Acquired Traits

12. History of Natural Selection Theory
Charles Darwin (1800s) – sailed on the H.M.S. Beagle and gathered data from organisms (fossils, finches, etc.)

13. Charles Darwin
From his data, Darwin hypothesized that all species descended from one or few original types of life
He concluded that the way species/organisms change over time was by natural selection

14. Process of Natural Selection
Must have a variation in traits of a population (different genes)
Must have environmental pressures that favor one variation of that trait over the other
Organisms with better traits survive better and longer, reproduce, and pass those good traits to offspring
Result = population better suited for environment

15. What causes evolution to happen?
Natural Selection
Geographic Isolation
Organisms become isolated by geographic barrier
If they are no longer able to reproduce, they may become two separate species (speciation)
Artificial Selection
Humans choose which traits to select for (ex. Dog breeding, genetic engineering, etc.)