Admixture occurs when individuals from two or more previously separated populations begin interbreeding. Admixture results in the introduction of new genetic lineages into a population
describes a situation in which some combinations of alleles or genetic markers occur more or less frequently in a population than would be expected from a random formation of haplotypes from alleles based on their frequencies
1) production of haploid gametes by meiosis with crossing over 2) matings between individuals which result in fusion of gametes to produce zygotes, resotres the full diploid complement of chromosomes 3) recombination occurs
Why did recombination probably evolve?
as a mechanism of DNA repair
offspring develop from unfertilized eggs
Whip Tail lizards and Amazon Mollies example
species that lost sexual reproduction and now reproduce asexually
Costs to sex
1) mix up of adaptions 2) searching for and attracting mates 3) dangerous (male spiders eaten, disease) 4) cost of meiosis associated with putting genes into males that cannot produce eggs
Benefits of recombination
1) increases genetic variation (more heterozygous individuals can mount a more effective defense against parasites than homozygous) 2) breaks up disequilibrium between advantageous and disadvantageous alleles 3) increases rate of evolution
Genetic Sex determination
dual sex chromosomes (ZW/ZZ, XX/XY) number of X chromosomes to autosomal chromosomes
Environmental Sex determination
Temperature (turtles), Local Sex Ratio ( fish), Population Density (nematodes)
Two Patterns of TSD in turtles
Pattern 1: single transition zone of temperature below which incubation yields nearly or totally 00 males, and above which only females are produced (females larger than males). Pattern 2: two transition zones, with males predominating at intermediate temperatures, and females at both extremes (females smaller than males)
Beginning life as a male and then switching to female
Protandry Male to Female characteristics
less common, anemonefish
beginning life as a female and then switching to male, implies presence of a male will prevent females from changing sex, and upon removal of that male, the female will switch sex
What kind of Population has highest possible intrinsic growth rate?
a population that is mostly females with just enough males to allow for fertilization
Why so many males in the human population?
all offspring have one male parent, and one female parent
Example of negative frequency dependence in sexes
if males are rare, then males will have a high fitness relative to females (each male would contribute to the next generation), the reverse is true for females
Local Mate Competition
organisms closely related to everyone around them, males would be competing with their brothers (Wasps)
Red Deer Example?
the cost of males and females are NOT equal, sons are more costly and dominant females will produce more sons
Discrete vs. continuous
What determines quantitative traits?
environment and genotype
Logic of QTL
1. cross to produce F1 offspring 2. Cross F1xF1 to produce F2 3. Determine phenotypes of F2
If distribution of QTL test varies?
then marker is linked
If distribution of QTL test does not vary?
then marker is not linked
Example of QTL test
Novelty trait linked to other traits. variation associated with dopamine receptor D4DR 48 base pair repeats n times
Broad Sense Heritability
extent that phenotypic variation is determined by genotypic variance, V(g)/V(p) = V(g)/ V(g) + V(e)
Narrow Sense Heritability
is the proportion of the variance resulting from additive genetic variance (h^2)
Galahs and Pink Cockatoos
switch eggs in nests, some behaviors stayed the same (heritable), some behaviors mimicked the foster parents (environmental)
Predicting evolutionary response to selection
R=h^2S need to know heritability and selection
Example of evolutionary response to selection
Tundra Flowers grew by 12% because bees prefer larger flowers, directional selection
individuals on one end does better
Individuals in middle do better
individuals in middle do worse (gets rid of most common phenotype, increases variation)