• Each chromosome has a partner
• Homologous chromosomes
• Resemble each other in size, shape & hereditary information
• Each homolog is from a different parent
  

• During Metaphase I
• Orientation of bivalents is random
  During Metaphase II
• Orientation of sister chromatids is random
  

• During Prophase I
• Synaptonemal complex forms
• Mixes the genes present in homologous chromosomes
• Results in new combinations not present in the chromosomes of the parental cells
  

• New combination of alleles from each parent
• Promotes heterozygosity
• Advantages include
  genetic diversity
  Bet-hedging to novel environments
  Multiple deleterious alleles can be bunched together and eliminated
  

• Each individual has a unique genotype
• Genotype is made up of alleles
  
  • Phenotypes determined by these alleles (and the environment)
• There is no guarantee that an allele will manifest
  Heterozygosity
• One of 2 genes (dominant allele) has a detectable effect on an organism's appearance
  

• Alleles are segregated, separated, from one another during meiosis
• Each gamete contains only one allele for each gene
• Offspring inherit 2 alleles for a gene
  One from each parent
  

• Punnett square
• Visual representation of the offspring inheritance patterns
• Monohybrid is a cross between 2 homozygous parents with different alleles.
  

• Gene pairs that are not related (homologs) segregate independently
• Gene pairs that are not linked segregate independently
  

• Phenotype of heterozygote is intermediate between those of parent homozygotes
• Snapdragons
  Red x white = pink
  

• Many populations have more than 2 alleles for a particular locus
• Punnett square theoretical crossing works similar
• Breeding experiments to determine dominance
  Figuring out alleles is complex
  

• Changes in the genetic makeup of an individual
  Point mutation
• Single nucleotide change
  Chromosome mutation
  Deletion
• Segments of chromosome are lost
  Duplication
• Part of the chromosome has doubled
• Inversion
  Piece rotates 180
• Translocation
  Exchange of parts between 2 nonhomologous chromosomes
  

• Multiple genes for one character
• Phenotype is cumulative result of combined effects of many genes
• Example abscisic acid
• Most traits
• Continuous variation
• Populations tend to have normal distribution
  

• Single gene with multiple effects on the phenotype
• Inheritance of a single gene which visibly influences several traits
  Ex: awn of wheat
  Wheat with awns have greater yield than those without awns
  

• Having more than two copies (2n) of a chromosome
• Autopolyploid
  Failed meiosis
  Self fertilization
• Allopolyploid
  Meiotic error
  Mismatch during mating
  Second mating creates matched pairs
  

• Wheat
• Result of sequential hybrid doubling and quadrupling
• Original ancestral species had 14 chromosomes
• Durum wheat
  

• Strawberry
• Chemically induced
• Prevent microtubule formation
  Required for meiosis to occur properly
  

• Polyploid mask deleterious recessive alleles
• Relax selection pressure
  Accumulate mutations that eventually result in beneficial trait
• 2 groups of ancient duplications
• Common ancestor of seed plants
  

• All of the alleles of every gene in a population make up the gene pool
• A population is a group of individuals of the same species that occupy the same region and can interbreed with each other
  

• Allele frequency
• Number of copies of an allele in a population divided by the total number of alleles for that gene in a population
• Genotype frequency
• Number of individuals with a particular genotype in a population divided by the total number of individuals in a population
  

• Number of copies of an allele in a population
• Divided by
• The total number of all alleles for that gene in a population
  

• Number of individuals with a particular genotype in a population
• Divided by
• The total number of all individuals in a population
  

predicts an equilibrium-unchanging allele and genotype frequencies from generation to generation-if certain conditions exist in a population

1. No new mutations
2. No genetic drift. The population is so large allele frequencies do not change due to random sampling effects
   No migration
3. No natural selection
4. Random mating
   
   
   

• Consider a dimorphic population (2 alleles) such as our red and white flowers with alleles R & r
• All alleles in the population add up to 100% or 1
• All genotypes in the population add up to 100% or 1
• Red & White flower examples
  Allele frequencies
  r = 0.38, R = 0.62;
  0.38 + 0.62 = 1
  Genotypic frequencies
  rr = 0.25, RR = 0.48, Rr = 0.27;
  0.25 + 0.48 + 0.27 = 1
  

• Genotypic frequency:
  RR= 0.38
  Rr= 0.24+0.24= 0.48
  rr= 0.14
• The frequency of gametes carrying a particular allele is equal to the allele frequency for a population in Hardy-Weinberg equilibrium.
  

The frequency of the dominant allele is represented by p
The frequency of the recessive allele is represented by q
Thus p+q=1
Therefore (p+q)2=1squared
And p2+2pq+q2=1

• Changes in a population’s gene pool from generation to generation
• Factors
  Mutation
  Natural selection
  Genetic drift
  Migration
  

• Random loss of alleles
• Acts most strongly in small populations relative to large
• Bottleneck effect
• Large population diminished suddenly
  

• Plants “choose” their mates
  Pollinator vectors
• Some of the individuals reproduce more than others
  

• Male-male competition
• Excess of pollen grains
• Pollen tubes can interfere with one another
  Female choice
• Barriers on stigma surface preventing germination
  

• Movement of alleles into and out of a population
  -Immigration
• Into
  Emigration
• Out of
  Can be impeded by
  The environment
  Life history
  

• One allele selectively advantageous
• In this example, 2 (triangle) has more vigorous offspring
• Over time, individuals with the 2 genotype are able to reproduce more and grow in numbers
• The overall vigor of the population grows
  

• Death does not mean natural selection has occurred
• Differential survival
• Survival due to phenotypes that are heritable
  Phenotype coded by genotype
  

• Within a population there is allelic variation arising from various factors such as mutations causing differences in DNA sequences
• Distinct alleles may encode proteins of differing functions
• Over the course of many generations, allele frequencies of many different genes may change through natural selection
• This significantly alters the characteristics of a species
  

• r = intrinsic growth rate
• N = population size
• K = carrying capacity
• dN/dt = population change over time
• Exponential growth
• dN over dt equals r times N
• Logistic growth
  dN over dt equals r times N times the quantity one minus N divided by K
  

• x = age
• Nx= number of individuals alive at age x
• Sx= proportion of individuals of age x that survive to age x+1;
  Nx+1/Nx
• lx= proportion of individuals that survive from birth (age 0) to age

• Calculate the net reproductive rate (R0)
• Calculated by taking the sum of the offspring/individual column.
• Represents the expected number of offspring an individual will produce over its lifetime in the population.

• Calculate the mean generation time (G)
• Calculated by taking the sum of the Age-weighted fecundity column and then dividing by the net reproductive rate
• Represents average time between two consecutive generations in the lineage of a cohort
• The average age between parent and offspring
  

• Calculate the intrinsic growth rate (r)
• Calculated by taking the natural log of the net reproductive rate divided by the mean generation time.
  

• a group of actually or potentially interacting species living in the same location.
• bound together by a shared environment and a network of influence each species has on the other.
• factors affecting interactions include
  

• At low prey and predator population sizes, prey increase exponentially
• As more food for predators is available, predator survival and reproductive success increases, resulting in predator population growth following that of their prey
  
  • As predator populations increase, prey death rate exceeds birth rate, resulting in prey decline
• As prey number declines, there is not enough food to sustain a high predator population and thus predator death rate exceeds that of birth rate
  

• dN/dt = rN-aNP
• dN/dt=rate of change with time of the prey population
• r=intrinsic rate of increase for prey
• N=number of prey individuals
• a=predator’s per capita attack rate
• Number of prey eaten per predator per unit time
  dP/dt = faNP-qP
• dP/dt= rate of change with time of predator population
• f=constant, indicating predator’s efficiency at converting the prey it has eaten into new predators
• q=predator’s per capita mortality rate
  

• Prey population change
• The number of prey N = 1200,
  rate of capture or the predation constant a = 0.004,
• Intrinsic growth rate, r = 0.7 = and
• Number of predators, P = 130?
  dN/dt = rN-aNP
• Predator population change
  N = 1200,
  a = 0.004,
• f = 0.025 predator birth constant,
• q = 0.12 predator death constant
  and P = 130 number of predators