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Chapter 10.3 Notes
The Theory of Natural Selection
**Key Concept: Darwin proposed natural selection as a mechanism for evolution**
I.
Several key insights led to Darwin’s idea for natural selection
a. Darwin noticed a lot of variation in domesticated plants and animals
b. Artificial selection is the process by which humans select traits through breeding
II.
Natural selection is a mechanism by which individuals that have inherited beneficial adaptations
produce more offspring on average than do other individuals
a. Heritability: the ability of a trait to be passed down
b. Struggle for survival due to overpopulation and limited resources
c. Darwin proposed that adaptations arose over many generations
III.
Four principles of the theory of natural selection
a. Variation: differences in individuals results from differences in the genetic material
b. Overproduction: having many offspring increases chance that will some will survive;
increases competition for resources
c. Adaptation: a certain variation that allows an individual to survive better than other
individuals
d. Descent with modification: over time, natural selection will result in species with
adaptations more suited for survival and reproduction
IV.
Natural selection acts on existing variation
a. Can only act on traits that already exist
b. Structures can take on new function in addition to their original function