NATURAL SELECTION AND FITNESS

LECTURE 8

Moths in UK

In the UK there were only peppered moths, until a new mutation arose that brought metallic moths however were always keep at low level of frequency due to predation

• Once Industrial Revolution took place, it changed the environment of the moth, causing selection to favor metallic moths

• Numbers of metallic moths decreased once again once depollution actions were made changing the environment of the moths once again

Flies

Flies natural have a alcohol dehydrogenase enzyme that helps detoxify ethanol to acetaldehyde

• Created two artificial environments with different level of the fast detoxify gene one environment with ethanol and another without

  • Found that in high ethanol environments this gene increased in frequency

Suviorship

How likely a zygote will reach adulthood ( how good a genotype is at surviving ) (l_ⁱⁱ)

Fecundity

Reproductive success an individual has ( how good a genotype is at producing offspring ) (m_ii)

Relative Fitness

Refers to genotype-speflic survivorship and fecundity ( w_ii=l_ii x m_ii or w_ii= 1+s ); how likely a genotype is going to survie and reproduce

Selection Coeffiencent

Refers to how strong natural selection acts against or for a specific genotype

• Deletrious allele: want s to be large s vaule to remove from population

• Benefincal allele: want s to be a large postive value to reach fixation as fast as possible in population

s=1-w_ii

Selective Sweep

When selection favors a benefinal mutation within a population allowing for fast fixation of said mutation/allele in population

• Netural genes attached to beneficial mutation will also increase in frequency and possibly reach fixation due to they being linked

  • Process known as hitchhiking which reduces genetic variation in a population