Transcript N.S. 100 Lecture 15 - PPT Evolution Spring 2009 Assignment Page

Lamarck = Inheritance of
acquired characteristics
Giraffe stretches neck over
several generations to reach
leaves high in trees
Lamarck
Natural selection – favorable new traits
resulting from random mutations are
passed on to succeeding generations
Darwin
Darwin = Proposes the
“Origin of Species”
(by natural selection)
5 year world cruise
Ancestral bird “adapts” (by natural selection) into various habitats
leaves
seeds
fruit
Vegetarian
insects
insects
Ancestor?
grubs
Uses tools
seeds
Woodpecker
cactus
Darwin’s Finches
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
% RESISTANCE
Add Antibiotic
Normal bacteria
Resistant bacteria
Dead bacteria
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
UV light
Thymine dimer
Radiation (x-ray) causes
chromosome damage
With and without
mutation
No mutation
mutation
No mutation
mutation
No mutation
No mutation
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
20,000
Cheetahs
 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
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 population
Population 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
33% purple
20% purple
33% purple
32% purple
Small population with
12.5% white and 87.5% dark
75% dark
25% white
100% dark
0% white
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
Light moth reproduces
more often – why?
Bird eats dark moth
Dark moth reproduces
more often – why?
Bird eats light moth
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
Review
4. Genetic Drift – accidental loss of individuals
5. Natural Selection – most fit reproduce more
often
SPECIES =
group of interbreeding populations
reproductively isolated from other populations
Are lions and tigers separate species?
Liger = lion x tiger
Are horse and donkey different species??
Horse
X
sperm
Donkey
egg
=
Mule (sterile)
No
meiosis
Ensatina eschscholtzii
Geographic
Isolation can lead
to differences and
new species
Becomes separate species as
mutations make them different
Ensatina eschscholtzii
Kaibab and Abert’s
squirrels separated
by Grand Canyon =
geographic isolation
Colorado
River
Geographic isolating mechanisms (fences)
prevent exchange of genetic differences between
dog breeds allowing differences to build-up
If population is geographically
isolated long enough, then behavioral
isolating mechanisms occur