Download Patterns and Mechanisms of Evolution

Agenda – March 3
• Population Notes Ch 23
Section 1 and 2
• Hardy Weinberg
Practice Worksheets
• HW: Finish Lab 8 and 9
• Field Trip Forms and
Money Due March 11th
Review
1. These terms are not the same, they are not
interchangeable. What is your definition?
Natural selection?
Adaptation?
Natural Selection
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Natural selection is the PROCESS that results
in evolution.
It "screens" traits that are available. It
doesn’t create new traits.
It favors those characteristics that fit the
specific current environment.
Adaptation is the change or the trait that
occurs over time so an organism fits better
with its environment.
Population Genetics and Speciation
* Natural Selection works on individuals but
is only apparent in a population as it
changes over time*
• Microevolution: Change in allele frequency of
pop/gen
– Natural Selection (Consistent matches env/org)
– Genetic Drift (Chance)
– Gene Flow (Between populations)
• Gene Pool: all alleles for all loci in a
population
The factors create genetic
variation - makes evolution
possible.
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Recombination and RNA Splicing: Genes are shuffled
Random pairing of gametes: Which sperm will be the winner?
Mutations
Environmental effects
Crossing Over/Ind Assortment: Meiosis
Cause phenotypic differences.
Characters that vary can be:
Discrete: purple, white flowers (one gene)
*** Quantitative: continuum, (multi genes)
Mutations
Ultimate source of new alleles
Somatic/Body cell – not inherited
Gamete/Germ cell – inherited change
- Point and frameshift
- 1 in 100,000 genes per generation (plant and animal)
- Less for prokaryotes
- ^reproduction ^rate
- HIV, 2 Days, No Repair Mechanisms
Hardy Weinberg
Used to assess if natural selection
causing evolution or other factors (If it
is not evolving, HW applies)
PKU (Recessive Metabolic Disorder)
• Affects 1 out of 10,000 babies in USA
• Assume:
– No new PKU mutations introduced (Condition 1)
– No preferential mating bcuz of disorder (Condition 2)
– No differential survival and reproductive success among
PKU genotypes (Condition 3)
– Large population, no genetic drift or gene flow
(Conditions 4 and 5)
• Reasonable assumptions for this disorder
Practice Question
• Recessive = q2 = 1 in 10,000 = .0001
• Therefore, q = .01
• Frequency of dominant allele = p = 1- q = .99
• We have to calculate number of heterozygotes.
• 2pq = .0198 or approximately 2% of USA population
Homework: Lab 8 and 9 Due Tmrw
Independent Practice Worksheet
March 4, 2016
Agenda:
Turn in Lab Journal
Finish Chapter 23 Notes
Teddy Graham Activity
HW: Practice Ques.
Wrksht and Video
Notes
Hardy Weinberg Answers
2. q=.6
p=.4
2pq=.48
Frequency of homozygous dominant 16%
3. 2pq = .48
48%
q=.6
36%
p= .4
16%
4. Homo Recessive 81%, Homo Dominant 1%, Hetero 18%
Frequency of Dom 10%, Frequency of Recessive 90%
5. Dominant phenotype 91%, recessive phenotype 9%,
Heterozygous 42% (This group is part of the dominant group)
Recall from Yesterday…
Three processes can change allele frequency.
Genetic Drift
Chance events can cause ∆ allele freq.,
Unpredictable, Esp. in small popu.
Fertile soil? Nutrients available? Sunlight? Wild moose?
Certain chance events have sig. impact
Bottleneck Effect Reduction
(Disease, Disaster)
Founder Effect – Increase
(Colonization)
Greater Prairie Chicken
19th- 20th Centuries
• Human Impact: Illinois Prairies to Farms
• Dec. popu., genetic variation
< 50 ckns between 2 popu.
< 50% Eggs hatching (^ harmful alleles)
• Translocation, add new alleles
Gene Flow
• In/Out Population (Travel)
– Introduce new alleles
– Higher rate than mutations
– Alter allele freq. ^ v
• Blending of popu.
– Combine single popu.
– Common gene pool
• Ex: Insecticide-Resistant
mosquitoes worldwide
Natural Selection can alter heritable traits in 3 ways…
Favors one extreme
(Large body size of
bears, conserving body
heat, survive winter)
Favors both extreme
phenotypes (Sm beaks
soft food and Lrg beaks
for hard food)
Favors Intermediate
(Birth Weight 6.68.8 lbs) Reduces
variation
Then why aren’T all
living things perfect?
• NOT GOAL ORIENTED.
• Acts on existing variations,
may not be ideal, can’t
demand needs
• Limited historical constraints,
ancestral anatomy
• Adaptations often
compromises (Opposable
thumbs)
• Nat. Sel. Interacts with Env.
And Chance (Unpredictable,
Limiting)
Teddy Bear Activity
• Groups of 3
• DO NOT EAT OR
INJURE THE BEARS