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- 1809-1882 British
- 1831- Done w theology school
- Naturalist on HMS Beagle 1831-1836 (5 years)
- Galapagos islands (off pacific s america) 6 weeks
- -Saw: toroises, mocking birds, finches, cacti, etc...
- Came home- thought/writing/reading/communication
- 1798 Essay
- Charles lyell 1830 geology (earth is old)
- Essay of 1842
- Not published
- 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:
- Gophers: digging abilities
- F: faster
- f: slow
- FF Ff ff
- Foxes eat ff --> FF Ff
- Example of natural selection - some genotypes have done better than others.
- Allele freq: Before: F 3/6 f 3/6
- After: 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.
- Example: 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.
- Ex: squirrels w longer fur survive through winter
- Ex: increased resistance to antibiotics in bacteria
- Ex: Plants around mine tailings
- Ex: 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)
- IT EXISTS-
- 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
- H: heterozygosity - % loci heterozygous in an individual (humans 7%)
- P: 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
- Allozyme studies
- 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:
- a) enzyme
- active site: 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)------> -
- Alleles neutral
- 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:
- Diploid organisms
- 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
- Genotype: AA, Aa, aa
- Number of AA individuals: N(AA)
- Total pop. size: N
- Freq of AA:. f(AA)
Total number of alleles in population: 2N alleles
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.
- Genotype: AA: 405/500
- Aa: 90/500
- aa: 5/500
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
- Given: f(aa) = .3 = q^2 --> square root of .3 = .55
- allele freq: f(T) = 1-.55 = .45
- Genotype freq:
- 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
- ex: founder effect -small group of organisms found a population.
- ex: 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
- ex: 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:
- gene flow
- non random mating
- genetic drift