Wize University Biology Textbook > Evolution
Charles Darwin
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Charles Darwin
Views Before Darwin
- Geoerges Cuvier: French scientist that studied fossils
- Fossils in strata
- Strata: Specific layers of rock that can be used to infer age of the layer (and the fossils within each stratum)
- Extinction must occur frequently through catastrophic events
- These events lead to fossils in the different strata
- Lamarck: French biologist that recognized species DO change over time
- Known for incorrect mechanism of evolution
- Believed species changed over evolutionary time scales by passing down acquired characteristics Example: Each generation giraffes would stretch their necks to reach high branches, and then they would pass these longer necks down to their offspring
- This is logically flawed!
Charles Darwin
- Wrote Origin of Species
- Unity: Many species resemble each other - based on all life descending from a common ancestor
- Diversity: Species in different environments acquired diverse modification (adaptations) Example: Finches on different islands are different, but all are similar and appear to be related
- Variation on a central theme (modification on the design of a common ancestor)
Natural Selection
- Organisms produce many more offspring than the number that survive
- However, populations are stable (don't increase or decrease)
- Resources are limited
- Therefore, organisms must compete to survive
- Variation exists among individuals
- Some of the variation is heritable
- Heritable: A trait that can be passed down to offspring
- Some variations will produce superior competitors
- Individuals with these advantages will be more likely to survive
- Therefore, there will be more individuals with these advantageous traits in the next generation
- Together these form the mechanism of evolution: Descent with Modification
- Species adapt to the environment over generations
- Natural selection must act on existing variation
- There has to be some trait present in the population for natural selection to act on
Wize Concept
It's important to note that an individual cannot evolve.
Evolution occurs over many generations as individuals with beneficial traits have more children that survive who also have these beneficial traits.
When you repeat that process over thousands of year, you eventually see the species change.
Practice: Scientist
Which scientist studied fossils and concluded that mass extinctions were common throughout history.
Practice: Darwin
Which of the following did Charles Darwin not believe in:
Practice: Natural Selection
What inference did Darwin draw from the observation that organisms produce more offspring than the environment can support?