1. Darwinian Evolution
Chapter 22

2. What you need to know!
How Lamarck’s and other notable predecessors’ views of the mechanism of evolution differed from Darwin’s.
The difference between structures that are homologous and those that are analogous, and how this relates to evolution.
The role of adaptations, variation, time, reproductive success, and heritability in evolution.

3. Preceding Darwin
Aristotle BC – Scala naturae: oragnization of life based on increasing complexity
Linnaeus – taxonomy: naming and classifying all organisms, binomial nomenclature: genus and species
Cuvier – father of paleontology, study of fossils leads to theory of catastrophism (mass extinction) which explains the boundaries between strata and the location of different species

4. Preceding Darwin
Hutton & Lyell – Theory of Gradualism (uniformitarianism): Earth geology changes slowly and continuously
The Earth must be VERY old
Darwin studied Lyell’s work

5. Preceding Darwin Lamark 1744-1829 – 1st theory of evolution
Use or disuse of body parts leads to their development or deterioration (acquired characteristics)
Inheritance of acquired characteristics

6. Early Darwin 5 year voyage on the HMS Beagle 1831-1836
Naturalist – collected plants, animals, and fossils
Major finds on the Galapagos Islands
Finches
Tortoises
Common ancestor

7. Late Darwin “Origin of Species”
Natural variation exists in all populations
All organisms produce many offspring with variations
All organisms compete for limited resources
Natural Selection
Descent with modification

8. Artificial Selection
Human selection of favorable traits over 100’s of generations
Darwin used this model to develop natural selection and descent with modification

9. Natural Selection
Darwin’s mechanism for evolution is natural selection (an explanation for adaptations)
What was Lamark’s mechanism?
Adaptations: characteristics that enhance an organisms ability to survive (i.e. desert fox – large ears; arctic fox – small ears)
Organisms that have advantageous heritable traits (fitness) survive and reproduce at a higher rate
Environmental changes may result in adaptations, and sometimes speciation (the founder effect)
Individuals do not evolve, Populations do!

10. Descent with Modification
Offspring are genetically different from their parents
As we move forward in time diversity increases (speciation)
As we move backward in time diversity decreases (fewer species)
If we go back far enough all species are related (ancient common ancestor)

11. Evolution Summed Up Evolution is change in species over time.
Heritable variations exist within a population.
These variations can result in differential reproductive success.
Over generations, this can result in changes in the genetic composition of the population.
Individuals do not evolve! Populations do!

12. Patterns of Evolution Divergent Evolution Convergent Evolution
2 different species evolve from a common ancestor (different adaptations)
Convergent Evolution
Different species show the same adaptations due to similar environments (analogous structures)
Parallel Evolution
2 different animal groups evolve similarly in separated environments (mammals and marsupials)
Coevolution
Both predators and prey adapt to each other over time