Unit 5 – Lecture 4
Feb 12, 2016
Unit 5 – Lecture 4
Darwin’s Five PointsObservations regarding natural selection:
populations have variationssome variations are beneficial / favorable
more offspring are produced than survivethose that survive will have favorable traitsbecause of this, a population will change
over time
Genetic EquilibriumRecall – natural selection affects
POPULATIONS not individuals
Gene Pool – the collection of genes within a populationallelic frequency – the frequency of certain
alleles within a population
Genetic Equilibrium – cont’dGenetic Equilibrium – a steady-state of
genetic material/information within a populationno new traits added, none removeddoesn’t really happen in nature
[will discuss why soon]
Genetic Equilibrium – cont’dHardy-Weinburg Law
can find out how many alleles are in population if you assume that there is genetic equilibrium at any single point in time
Discuss
List and explain Darwin’s Five Points.
Name and explain reasons why genetic equilibrium
does NOT exist in nature.
Genetic Equilibrium – cont’dGenetic Equilibrium could be achieved if:
there is a large breeding populationno selection
all traits must be as favorable than others to maintain the same amounts of each allele
random mating existsif there is sexual selection, certain traits
would be favorable…which would change the amounts of each allele in the population
Genetic Equilibrium – cont’dGenetic Equilibrium could be achieved if:
no change due to mutationsany loss or gain of alleles would
change the genetic ratiosno immigration or emigration
when organisms leave, they take with them their traits
when organisms arrive, they bring in new traits
Genetic Equilibrium – cont’dGenetic Equilibrium does not exist because of…
selectionnatural or otherwise –
changes amount of certain genesmutation
loss or gain of info – changes amount of certain genes
gene flowemigration / immigration
Genetic Equilibrium – cont’dGenetic Equilibrium does not exist because of…
genetic driftsmall populations exist in which certain genes
are more prevalent than in the general populusAmerican Indians do not have blood group BAmish – marry within their own community, so
more likely to have certain recessive conditions likepolydactyly [extra fingers]
Genetic Equilibrium – cont’dGenetic Equilibrium does not
exist because of…natural disasters /
mass illnesscause the
“bottleneck” effect
Discuss
Again, summarize the reasonswhy genetic equilibrium does NOT exist in nature.