Natural Selection (2/7) Flashcards
Thomas Malthus’s “Principle of Population”
Malthusian Theory: predicts population size increases and a geometric rate but there must be some sort of check to prevent insane amount
- think the Chess Board multiplying example
First Papers on Natural Selection (by Darwin and Wallace)
- both arrived at the same conclusion of Natural Selection but Darwin received most of the credit for the idea
Origin of Species
Darwin’s book
- provided the central tenets of evolution by natural selection
Three Requirements for Natural Selection
- ) Variation: offspring are NOT exact copies of parents (mutations and mixing of genes)
- ) Inheritance: offspring inherit combination of traits from parents
- ) Differential Reproduction: individual with any slight adaptive edge has greater chance of producing offspring
**4.) Overpopulation: many more offspring produced than can survive (this isn’t necessarily one but it is an important factor)
Genotype
internally coded, inheritable information carried by all life that is the “blueprint” or set of instructions for building and maintaining a living organism
Allele
the variant form of a given gene
Phenotype
the outward, physical manifestation of the genotype;
the set of observable characteristics of an individual resulting form the interaction of its genotype with the environment
Ecophenotype
morphological changes caused by varying environmental-nutritional conditions rather than genetic differences
- not heritable so it doesn’t play a direct role in natural selection
Fecundity
the ability to produce an abundance of offspring
Types of Natural Selection
- ) Stabilizing Selection
- ) Directional Selection
- ) Disruptive/Diversifying Selection
- ) No Selection/Drift
Stabilizing Selection
selection against the extremes in a population; results in the maintenance of the status quo around an optimum
- i.e. timing of spawning, mating calls in frogs, flowering
- can decrease variability within a population
Directional Selection
a type of selection where a single phenotype is favored
- causing the allele frequency in the population to shift in one direction over time
- i.e. the color of desert mice,
Disruptive/Diversifying Selection
the selection for extremes in a population
- i.e. the color of fur in Himalayan rabbit fur
No Selection/Drift
no differential reproduction; all forms are equally successful