Natural Selection Flashcards
Natural Selection
The process by which certain inherited traits make it easier for some individuals to thrive and multiply, changing the genetic makeup of populations over time
Charles Darwin
Identified the process of natural selection in his book Origin of Species in 1859
Genetic drift
Random changes in how frequently some alleles show up
What is the most effective cause of evolutionary change
Natural Selection
Where did Darwin begin to formulate his theory
Voyage on the HMS Beagle in 1830’s to the Galapagos
Adaptations
The ways in which organisms seemed to be nearly ideally shaped to enhance their survival and reproduction in specific environments Ex: variation of beaks
What were the beaks shaped like depending on their food source
Insects: skinny and pointy
Hard seeds: thick
Cactus fruit: sharp
Fitness
Ability to survive and create offspring
4 ways to describe natural selection
- Different members of a population have all kinds of individual variations (phenotypes)
- Variations are heritable and can be passed on to offspring
- Populations can have more offspring than resource “struggle for existence”
- Heritable traits lead to variations in their survival and reproductive rates
Modes of Selection
Directional Selection Stabilizing Selection Disruptive Selection Sexual Selection Artificial Selection
Directional Selection
Favored trait is at one extreme end of the range of traits
Stabilizing Selection
Favors the majority that are well adapted to an environment
Disruptive Selection
Favors extreme traits at both ends of the spectrum and selects against common traits
Sexual Selection
Struggle between individuals of the same sex (generally males) for the possession of the other sex
Artificial Selection
Encourage the selection of some traits and discourage others
