Download Evolution of Populations

Evolution of Populations
Genes and Variations
Genetic Variation and Gene Pools
 Variation is studied in populations
 Gene Pool: consists of ALL genes,
including different alleles (ex: R and r)
 Relative Frequency: number of times an
allele occurs in a pool
 Example - B (black fur)is at 40%
frequency and b (brown fur) is at 60%.
 Why is Black Fur (B)more common if it
is only 40% of the alleles?
Evolution is the change of frequency
of the alleles!
 If the numbers change over time, then the
population is evolving.
 You try it: The gene for white moths is W,
and for black moths is w.
 What
do you think the original percentages were
before the industrial revolution?
 What about after?
 Are they evolving?
How do we get variation?
1. Mutation: change in DNA sequence,
some are good and some can be
“bad” for the species
2. Gene Shuffling: sexual reproduction
and crossing over gives a new set of
DNA each time we reproduce
Different Phenotypes
 Some traits are simple and some are
complex ex: widows peak is caused by
a single gene
 Single Gene Trait: has 2 alleles only
 Polygenic Traits: 2 or more genes
control the outcome
 This leads to more phenotypes and
variation. Ex: How many shades of eye
color are their?