Download Microevolution Notes

DO NOW
1. Who is the father of evolution?
2. Explain why Lamarck’s theory of use and
disuse is no longer accepted?
What is Microevolution?
Change in a
population’s
alleles over a
period of time
Calculate allele
frequencies
Allele
Two different forms of a gene (portion of DNA
that codes for a trait)
Three different combinations
of Alleles
Homozygous Dominant: DD
Heterozygous: Dd
Homozygous Recessive: dd
Allele Frequencies
A measure of
how often
(frequency) an
allele is
apparent in a
population.
What is Natural Selection?
“Survival of the
Fittest”
The best
adapted
organism will
survive and
pass traits onto
offspring
Natural Selection Flowchart
Observation #1
Organisms overproduce: Every
population has the ability to grow
Observation #2
Every population has limited resources
Conclusion #1
Competition for resources; not all
organisms survive
Hyena
Observation #3
Every individual in a population is different
in structure and behavior. Ex-pattern,
speed, agility, etc
Conclusion #2
There is variation within populations.
Observation #4
Organism better suited to their environment
live longer & have more babies,
Conclusion #3
Natural Selection-Survival of the Fittest:
Best adapted organism will survive
Observation #5
Survivors will
pass their traits
on to their
offspring.
Conclusion #4
Descent with modification. Evolution has
occurred. There could be a change to the
population.
WATCH ME!!!!
Natural Selection &
Populations
Directional Selection
• One extreme is selected for causing the
other extremes to be selected against.
Example Directional
Selection: Peppered Moths
Example #2: Pesticide Resistance
• When insecticides are first used, vulnerable insects
die.
• Few individuals that are “immune” to the
pesticide, survive and live to pass on that trait.
Example #3: Antibiotic Resistance
• Antibiotics first came into use in the 1940s. Overuse has led to increase
in resistant forms of bacteria.
• Over-prescribed antibiotics include penicillin and streptomycin.
• Overuse of antibiotics has selected for resistant strains, which now
threaten to become more predominant than the susceptible ones.
Stabilizing Selection
• Average individuals favored
• Intermediate forms are favored while the
extremes are selected against.
Stabilizing Selection Example #1: Human Babies
• Humans who weigh about seven pounds at birth have the greatest
survival chances.
Example #2
• Siberian Husky is a medium dog weighing between
35-60lbs.
• These dogs have strong pectoral and leg muscles
allowing it to work through the snow.
• How is this an example of stabilizing selection?
Disruptive Selection
• The intermediate (middle) is selected against while
both extremes are selected for.
Disruptional Selection Example
Butterflies selected for..
Selected against…….