1. Theories and Patterns of Evolution
Chapter 15

2. Theories of Evolution
Biological Evolution: the change of populations of organisms over time
New life forms are really modified versions of older ones in same geographic area
2 Explanations:
Lamarck’s
Darwin’s

3. Jean Baptiste Lamarck
Thought acquired traits (learned, not inherited) could be passed to offspring
Not True!!

4. Charles Darwin
Spent 5 years aboard H.M.S. Beagle traveling world & recording observations
Animal adaptations and geographic changes required VERY LONG periods of time to occur

5. Modern Evolutionary Thought
Natural Selection: organisms best suited to their environments will reproduce more successfully
Over time, # organisms with favorable traits increases within a population
Artificial Selection: Breeding organisms with specific traits to produce desired offspring

6. Modification by Natural Selection
The Process:
1) Organisms better equipped to survive environment will produce more offspring
2) Eventually, popltn made up of only successful members
3) Over time, an entirely new species may form!!

7. Descent with Modification
“Newer forms appearing in fossil record are actually modified descendants of older species”
Implies that ALL species descended from only a few ancient organisms

8. Adaptation Populations adapt as their # of favorable traits increases
The types of traits that are favorable depends on the environment
Examples:
Mimicry: a harmless species resembles a dangerous one; both are avoided by predators
Penicillin-resistant bacteria, rose thorns, etc.
Camouflage: enables species to blend with surroundings
As genetic makeup of popltn changes, evolution occurs

9. CAMOUFLAGE
MIMICRY

10. Patterns of Evolution
The pattern & speed with which organisms adapt is dependent upon their environment
3 Patterns:
1) Coevolution
2) Convergent Evolution
3) Divergent Evolution

11. Coevolution
Coevolution: the change of 2 or more species in close association
i.e. predator/prey; parasite/host; plants/herbivores

12. Convergent Evolution
Convergent Evolution: occurs when environment selects phenotype
Results in similar phenotypes of different organisms
i.e.: body shape of dolphin (mammal) & shark (fish)

13. Divergent Evolution
Divergent Evolution: when 2 related species become more dissimilar
Adaptive Radiation: when different species evolve from common ancestor
i.e.: Galapagos finches