BIO220H1 Study Guide - Final Guide: Estuary, Limiting Factor, Milankovitch Cycles

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15 Apr 2012

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BIO220 Final Exam Study Sheet
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Ecology and Evolutionary Genetics
Mitochondria DNA can track maternal lineages
Y chromosome can track paternal lineages
Elephant social system
o Males are generally still reproductive when their daughters mature
o Since it’s hard to observe elephants (which live really long) they just tracked their
Found that courtship behaviours are directed away from kin
Migrating wolves
o Some wolves migrate, some don’t
Northern wolves follow migrating caribou south for winter and back north for
Southern wolves prey on deer, moose, elk, etc.
Are territorial
o Different wolves might show genetic differences in neutral markers
o Spatial divide of alleles seems to indicate genetic differentiation; Quantify with Fst
Fst = 1 for complete differentiation
Fst = 0 for non differentiation at all
o mtDNA: Fst = 0.28
o Y-chromosome: Fst = 0.03
o Wolves generally stay with their mother’s pack; so mtDNA tends to stay in the same
pack resulting in higher differentiation
Human marriage customs
Patrilocality (Females move; males stay)
Matriolocality (Females stay; males move)
High Y-chromosome differentiation
Low mtDNA differentiation
Low Y-chromosome differentiation
High mtDNA differentiation
Human Agricultural Coevolution
Many Europeans have lactase production throughout adulthood
Convergent evolution
o Different human populations that raise dairy all have higher chances of being lactose
tolerant later in life
Selection affects the genome means we should expect
o Difference in fate of mutants that change amino acids
o Low variability in genome areas that are not under selection
o More differentiation of genome areas that are under selection pressure
o Synonymous No change in amino acid
o Replacement (non-synonymous) Change in amino acid
o For beneficial mutations, dn/ds > 1
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BIO220 Final Exam Study Sheet
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o Genetic Hitchhiking: As beneficial mutations become fixed in a population, they drag
with them nearby mutations
Region size depends on rate of recombination
o Gene for armor plating in freshwater vs sea water fish shows high Fst
Humans populations that eat more starch have higher numbers of the amylase gene
Genetic Diversity in Agricultural Systems
60% of our food energy from rice, maize and wheat
Center of Origin
o Crops originated in areas where the genetic diversity of their wild ancestors is the
Vavilov center of diversity
o Lysenko discovered induction of early flowers in biennial crops by applying cold
o Caused by epigenetics
But is reset during meiosis so that it doesn’t carry over into next generation
Lead to backwards Soviet biology and genetics
Domestication of crops causes
o Severe bottleneck
o Strong artificial selection
o Reduced genetic variation
Measured by
H: average frequency of heterozygous individuals per gene locus
P: proportion of gene loci that are polymorphic
: Average number of nucleotide differences per site for any randomly
sampled pair
Domestication of Maize from Teosinte
o Maize is corn
o Domestication 10 000-5 000 years ago
o Both bottle neck and selection reduce effective population size (Ne)
Effective size is the adults that breed, usually less than Census size (N)
o Selected loci show greater reduction in Ne compared to bottleneck which produces
genome wide reduction in Ne
o Test if a gene is selected for by looking for evidence of more severe bottleneck
o 2-4% of teosinte genome experienced strong artificial selection
As detected in imprint in genome
Extrapolated to 1200 genes
o Long term selection experiment of 100 generations of selection on corn for protein and
Limits to artificial selection not reached
Due to many genes affecting these traits
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BIO220 Final Exam Study Sheet
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o Use existing genetic variation and planned breeding
Score crop varieties for gene of interest and identify markers that co-segregate
Selectively breed genetic marker into crop variety; gene of interest should
Eg. Vitamin A and maize
Find SNP (single nucleotide polymorphisms) that are correlated with B-
carotene production
o Pest management
Potato famine
Potatoes are clonal
Oomycete (Phytophthora infestans- fungus-like eukaryote that is not a
fungi) infested it
Shows the risk of monocultures lacking genetic variety
Ecology and Evolution of Harvested Populations
Simple population growth model: 
 
o N= abundance
o t= time
o r= intrinsic rate of population growth of species
o K= carrying capacity
As N K, dN/dt 0
As N 0, dN/dt rN
Density-dependent growth rate limit population size
o Tern bird carry capacity on islands limited by nesting space
Ideal harvesting strategy: harvest K/2 individuals per year so population is at max growth rate
o Despite the maximum sustained yield there is economic pressure to harvest more
This leads to extinction
Evolution of harvesting
o Size thresholds means that little fish are selected for
o Size of antler racks and size of horns in sheep also selected for smaller ones
o Discrete Mendelian traits
Traits with discrete qualitative categories
o Quantitative Traits
Traits you can measure quantitatively
Lots of genes
Each gene effects phenotype in small way
Influenced by environment
Cannot infer genotype of gene from phenotype
Examining frequency of SNPs or alleles cannot predict phenotypic value
Work with statistical descriptions
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