Card Set Information
1831- Done w theology school
Naturalist on HMS Beagle 1831-1836 (5 years)
Galapagos islands (off pacific s america) 6 weeks
: toroises, mocking birds, finches, cacti, etc...
Came home- thought/writing/reading/communication
Charles lyell 1830 geology (earth is old)
Essay of 1842
Got a letter from naturalist Alfred Russell Wallace
July 1st 1858 - joint papers given by wallace and by darwin
Published "origin of species"
Ideas- world is not static, it is changing
Change could be spoken as "evolving"
Evolution is "Gradual"
Natural selection is a process / results in evolution
Phenotype / Genotype:
Group of organism, interbreeding, in 1 area, in 1 species
at the genes in a population
biotic factors - Living
abiotic factors - non living
Natural Selection -
Differential perpetuation (survivial/reprodcution) of genotypes
(some genotypes do better than others)
1. organisms can reproduce sexually
2. there is inheritable variation
3. testing of organisms by environment
EXAMPLE OF NATURAL SELECTION:
: digging abilities
FF Ff ff
Foxes eat ff --> FF Ff
Example of natural selection - some genotypes have done better than others.
: Before: F 3/6 f 3/6
: F 3/4 f 1/4
Change in allele frequencies:
Natural Selection is a process and results in microevolution
Types of NS: stabilizing NS
1. Stabilizing N.S.
: human birth weight
Those on ends of curve are at a disadvantage
individuals at one end of the curve are at an advantage at other end they are at a disadvantage.
: squirrels w longer fur survive through winter
: increased resistance to antibiotics in bacteria
: Plants around mine tailings
: moth coloration: Melanistic moths *industrial melanism)
Pre 1850- moths were light, mostly
Post 1850- many moths are dark
both Ends of curve are at an advantage (bird beaks)
Any function or structure that produces better adjustment of organism to environment.
Natural selection (process)---> adaptation
Change in allele frequencies through time
(NS) process ----> microevolution
2 or more species interacting, and they are selective force on other. (deer and wolves)
1. origin - mutation
2. How is it observed / quantified?
a) morphological variation (ex flower color)
b) enzyme variabilty -
allozymes- alternate forms of an enzyme
-coded for by same locus
-gel electrophoresis may tell them apart
: heterozygosity - % loci heterozygous in an individual (humans 7%)
: polymorphism - % loci polymorphic in an population (humans 38%)
c) variation in DNA - more vairabilty in dna than in enzymes.
aa - diff codons --- variability
d) eq of variabilty - hemoglobin molecule (sickle cell anmenia)
Higher in africa - carrier for sickle cell - immune to malaria
H: heterozygous %
P: polymorphism %
percent heterozygous (humans 7%)
percent polymorphic (humans 38%)
Arguments for variability:
Degeneracy of genetic code
Traits like ABO blood types
Recent DNA sequencing work
Degeneracy of genetic code:
same a.a. --- codon 1, codon 2, codon 3
variabilty in codons
some studies, diff allozymes are found more in diff. environments.
Barheaded goose- hemolains - high evelation
Andean goose - andes - high elevation
Both have allozymes of hemoglobin that carry O2 better.
Recent DNA sequencing work:
: less variability
away from active site
: more variabilty
b) much dna is non-coding (more variabilty)
A little dna codes for protein (less variabilty)
+------> neutral(most)------> -
studied at POPULATION geneticits
Look @ allele freq and genotype freq. (mathematical)
Change in allele freq.
-Diff. agents/forces that can change allele freq.
ex) natural selection
Basic assumptions / Starting point for allele freq:
Hardy Weingberg Equilibrium:
random mating = panmixia
assume no mutation, no NS, no immigration
population is large
1) no mutation
2) no immigration
3) random mating
4) pop. siz is large
5) No NS
Hardy weinberg equilibrium:
If above assumptions are true, then distripution of genotype and allele freq stay constant.
IF NO CHANGE = NO CHANGE
Locus with alleles A and a
: AA, Aa, aa
Number of AA individuals
Total pop. size
Freq of AA:. f(AA)
Total number of alleles in population: 2N alleles
f(A) = p
f(a) = q
p= 2N(AA) + N(Aa) / 2N
q= 2N(aa) + N(Aa) / 2N
Freq. of AA =
f(AA) = N(AA) / N
Calculate genotype freq. and allele freq.
: AA: 405/500
Example: PTC = T, t
TT Tt tt (nontaster)
american causasians: 70% tasters
30% non tasters
What is genotype and allele freq.
f(TT) = p x p = p^2
f(Tt) = 2pq
f(tt) = q x q = p^2
: f(aa) = .3 = q^2 --> square root of .3 = .55
: f(T) = 1-.55 = .45
f(TT) = p^2 - .45^2 = .202
f(Tt) = 2pq = .495
f(tt) = .3
Hardy weinberg equilibrium assumed:
Relax the hardy weinberg assumptions:
1) mutations exist (origin of variation)
(low rates 10^-4 to 10^-6 mutations/locus/generation)
How important is mutation in changed allele freq?
A <-----> a
u= "mu" rate of mutation --->
v= "nu" rate of mutation <----
Say u= 10^-5 and v= 10^-4
A<----a-mutation is bigger
equilibrium vale of p:
p = v / u+v
p = .91 = f(a) ----50,000 generations to get to equilibrium
Mutation is not a strong force in changing allele freq.
For NS to occur and evolution:
-variation among individuals in a pop.
-result in diff # of offspring
- variation must be genetically inherited
Large pop. size assumptions:
"genetic drift" - change in allele freq. due to change
: founder effect -small group of organisms found a population.
: bottle neck effect -disaster, pop. size gets small
Evolution change at and above species level
species: concepts of species
a) Morphology (morphological concept) form "looks like" "good morphological species"
b) Biological species concept- interbreeding ability (cant use in fossils)
production of species
One kind os speciation:
involves geographic isolation
2 populations - slightly diff. gene pools
experience diff mutations
experience selection pressures (NS)
2 diff pop ---> 2 diff species
production of several species
: galapagos finches
If two diff groups met again what happens?
REPRODUCE OR STAY ISOLATED (DO NOT REPRODUCE)
Depends on reproductive isolating mechanisms- have they evolved?
Properties of organisms which prevent interbreeding
1.) ecological RIM (reproductive isolating mechanism)
-potential mates do not meet
2.) Temporal RIM-
2 groups reproduce @ diff. times
insects / amphibians / plants
philisophical - final causes exist in nature
5 agents of evolutionary change:
non random mating