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Lamarck
Lamarck = Inheritance of acquired characteristics
Giraffe stretches neck over several generations to reach
leaves high in trees
Darwin
Natural selection – favorable new traits resulting from random mutations are passed on to succeeding generations
leaves fruit
Vegetarian
grubs
cactus
Uses tools
Woodpecker
insectsinsects
seeds
seeds
Ancestor?
Darwin’s Finches
Ancestral bird “adapts” (by natural selection) into various habitats
Microevolution:Change in the gene frequency within a population
Provides new genetic material for new traits …… without which all life would look the same ….. like the first life.
Many bacteria, including resistant variety
Expose all bacteria to antibiotics;
most normal die
Resistant bacteria multiply
and dominate
Entire infection
evolves into resistant
strain
Normal bacteria
Resistant bacteria
Dead bacteria
Add Antibiotic
% R
ES
IST
AN
CE
Example of microevolution
Causes of microevolution:
1. Mutation – nucleotide or chromosome
2. Non random mating – mate selection
3. Gene Flow - migration
4. Genetic Drift – accidental loss of individuals
5. Natural Selection – most fit reproduce more often
Factors that will cause microevolution:
1. Mutation – nucleotide or chromosome change
2. Non random mating – mate selection
3. Gene Flow - migration
4. Genetic Drift – accidental loss of individuals
5. Natural Selection – most fit reproduce more often
Non random mating
The wolf is probably close to natural dog if dogs allowed to mate freely
Specific breeds of dog result if dogs are only allowed to breed with others in the same breed
Extreme example of nonrandom mating = inbreeding
Results in mostly homozygous genotypes (e.g. HH or hh)
Cubs low survival rate
Susceptible to disease
Males have low sperm count
Only chance for new genes is through mutation
20,000 Cheetahs
Factors that will cause microevolution:
1. Mutation – nucleotide or chromosome change
2. Non random mating – mate selection
3. Gene Flow - migration
4. Genetic Drift – accidental loss of individuals
5. Natural Selection – most fit reproduce more often
Gene flow (migration) Genes for the brown beetle move to green
populationPopulation A = 100% green Population B = 100% brown
Factors that will cause microevolution:
1. Mutation – nucleotide or chromosome change
2. Non random mating – mate selection
3. Gene Flow - migration
4. Genetic Drift – accidental loss of individuals
5. Natural Selection – most fit reproduce more often
Genetic Drift: accidental loss of members of a small population
20% purple
33% purple
33% purple
32% purple
Factors that will cause microevolution:
1. Mutation – nucleotide or chromosome change
2. Non random mating – mate selection
3. Gene Flow - migration
4. Genetic Drift – accidental loss of individuals
5. Natural Selection – most fit reproduce more often
Bird eats dark moth Bird eats light moth
Light moth reproduces more often – why?
Dark moth reproduces more often – why?
Best adapted moth reproduces more offspring
Natural Selection does not give an organism an adaptation simply because it will do better with it.
– Adaptations occur by chance mutations
Factors that will cause microevolution:
1. Mutation – nucleotide or chromosome change
2. Non random mating – mate selection
3. Gene Flow - migration
4. Genetic Drift – accidental loss of individuals
5. Natural Selection – most fit reproduce more often
Review
SPECIES =
group of interbreeding populations reproductively isolated from other populations
Are lions and tigers separate species?
Liger = lion x tiger
Ensatina eschscholtzii
Geographic Isolation can lead to differences and
new species
Becomes separate species as mutations make them different
Geographic isolating mechanisms (fences) prevent exchange of genetic differences between
dog breeds allowing differences to build-up
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