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Lecture 2

PSYC 3100 Lecture Notes - Lecture 2: Genetic Drift, Allele Frequency, Natural Selection

Course Code
PSYC 3100
Pat Barclay

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Lec 2
“Natural selection is a non-random difference in reproductive output among replicating
entities, often due indirectly to differences in survival in a particular environment, leading to an
increase in the proportion of beneficial, heritable, characteristics within a population from one
generation to the next.”
- Gene frequency
o Genes are transmitted to the next generations
o Evolution change in gene frequency
Not better or for worse, just change
o Genotype
Genetic make up of that organism
o Phenotype
Organisms observable characteristics (how does it smell, act, how it
builds, ex: spiders build different webs)
o Genotype + Environment = phenotype
Four Main Mechanisms in Selection
- Natural selection
- Mutation
- Migration
- Genetic drift
Competition: the idea that not all organisms that are born will be able to reproduce
Heritable Variation: individuals differ (act, smell), capable of being passed off to one’s offspring
- (ABCD) (XWYZ) = (ACYZ) individuals that have offspring can get brought to next
generation. Mutations occur, as offspring may have (G or F)
Differential reproduction: some individuals reproduce more, some leave more babies, as a
result, if they are leaving more generations as babies they will be more prevalent
- individuals are not evolving; it Is the population that changes as the genes do
Genetic Drift: change in gene frequency that is random with respect to the effects of the gene
- imagine that lighting happens to come down and whip out families with blue eyes
- on average cancel out
Reproductive Success (RS)!
- psychological benefits are not enough
- Must be beneficial immediately, if its beneficial now it will increase within next
Misconceptions of Evolution (Sheet as a study guide) (Written in notebook)!!
- Evolution has a purpose
- Evolution does not equal progress, some things may evolve that are not good (viruses)
- Evolution does not have a single entity or goal that keeps things in a particular direction
or a certain way
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