Transcript Chapter 16

Chapter 16
Evolution of Populations
Variation and Gene Pools
• Gene Pool :All genes (and diff’t alleles)
present in a population
• Relative frequency: how often an allele
shows up in a gene pool
• Evolution: is a group process “ any
change in the relative frequency of alleles
in a population”
Activity
Long 2nd
toe
Gene Pool
Relative
Frequency
Pinky toe
Longer- 4 Present- all
Shorter- 11
Equal- 6
Longer – 19%
PinkyShorter – 52%
100%
Equal – 29%
Hair on
toes
Hair- 20
No hair-3
hair- 87%
- no hair-13%
Evolution of the toe
• Toes are short, which make humans great
long distance runners
• Short toes are great for push off during
running (toes are for balance too)
• The pinky toes – are not used for
running…so it may be possible that people
may start being born without them…
Sources of genetic variation
• Mutations: may occur because of a
mistake in DNA replication or radiation and
chemicals
• Gene Shuffling: normal….
- you don’t look exactly like brothers and
sisters
- you don’t look exactly like your parents
Gene Shuffling Activity
MOM GENES
DAD GENES
KID 1
KID 2
KID 3
Single Gene Traits
• Controlled by one gene
• 2 alleles, dominant and recessive
• ACTIVITY
• Tongue
rolling:
• Widow’s
peak
Hitchhiker's Thumb
Regular Thumb
Polygenic traits
•
•
•
•
Traits controlled by 2 or more genes
Ex?
“It’s NOT black or white”
-phenotypes would result in a bell curve