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Exam 5, Screenshot 2022-12-02 11.12.41 AM, Screenshot 2022-12-02 11.14.42…

- - - - 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
      - Mutations
        
        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
        
        No crossing over
        
        Fail to mix alleles across homologs
        
        Chromosome inherited same as parent
        
        Only 2 gamete types possible rather than 4
        
        Polygenic inheritance
        
        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
        
        Epistasis
        
        One gene interacts with another
        
        May interfere or mask
        Ex: digitalis petal color
        
        One gene impacts red intensity
        Pigment location
        w throughout corolla
        
        Linkage
        
        4 haploid genotypes
        
        Not produced in equal numbers
        Recombinants less abundant
        Parentals more abundant
  - - - Selfer
        
        Small petals
        
        Flower early
        
        Seasonal droug
        
        Physiologically escape?
        
        Outcrosser
        Large petals
        Flower late
        Seasonal droug
      - Polyploidy
        
        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
        
        Polyploid example
        
        Wheat
        
        Result of sequential hybrid doubling and quadrupling
        
        Original ancestral species had 14 chromosomes
        
        Durum wheat
        
        Polyploid example
        
        Strawberry
        
        Chemically induced
        
        Prevent microtubule formation
        Required for meiosis to occur properly
        
        Evolutionary significance
        
        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
- - - - During Metaphase I
        
        Orientation of bivalents is random
        During Metaphase II
        
        Orientation of sister chromatids is random
      - Crossing over
        
        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
        
        Sexual reproduction
        
        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
      - Principle of Segregation
        
        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
        
        Monohybrid cross
        
        Punnett square
        
        Visual representation of the offspring inheritance patterns
        
        Monohybrid is a cross between 2 homozygous parents with different alleles.
        
        Principle of Independent Assortment
        
        Gene pairs that are not related (homologs) segregate independently
        
        Gene pairs that are not linked segregate independently
        
        Dihybrid example
        
        Same as previous video
        
        For reference
        
        Parental
        True breeding
        Homozygous
        
        F1
        First filial generation
        Heterozygotes
- - - - 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
      - Allele Relative Frequency
        
        Number of copies of an allele in a population
        
        Divided by
        
        The total number of all alleles for that gene in a population
        
        Genotype Relative Frequency
        
        Number of individuals with a particular genotype in a population
        
        Divided by
        
        The total number of all individuals in a population
        
        Hardy-Weinberg equation
        
        predicts an equilibrium-unchanging allele and genotype frequencies from generation to generation-if certain conditions exist in a population
        
        No new mutations
        
        No genetic drift. The population is so large allele frequencies do not change due to random sampling effects
        No migration
        
        No natural selection
        
        Random mating
        
        Actual Allele Relative frequencies
        
        45 red flowered, homozygous plants
        
        25 red flowered, heterozygous plants
        
        23 white flowered plants
        
        45 RR
        
        25 Rr
        
        23 rr
        
        Actual Genotypic frequencies
        
        Phenotypes
        
        45 red flowered, homozygous plants
        
        25 red flowered, heterozygous plants
        
        23 white flowered plants
        Genotypes
        
        45 RR
        
        25 Rr
        
        23 rr
        
        Frequencies in populations add up to 1
        
        2 more items...
- - - - Change in one of the nucleic acids
        
        Some are apparent in phenotype
        
        Source of all new alleles
        
        Must be in gametes to be inherited
      - Polymorphism
        
        Dimorphic
        
        2 phenotypes
        
        Dominant-recessive systems
        
        Polymorph = many phenotypes in a population
        Example: Aquilegia
        Color variation
        
        Genetic drift
        
        Random loss of alleles
        
        Acts most strongly in small populations relative to large
        
        Bottleneck effect
        
        Large population diminished suddenly
        
        Nonrandom mating
        
        Plants “choose” their mates
        Pollinator vectors
        
        Some of the individuals reproduce more than others
        
        Nonrandom Mating: Sexual Selection
        
        Male-male competition
        
        Excess of pollen grains
        
        Pollen tubes can interfere with one another
        Female choice
        
        Barriers on stigma surface preventing germination
        
        Migration, Gene flow
        
        Movement of alleles into and out of a population
        -Immigration
        
        Into
        Emigration
        
        Out of
        Can be impeded by
        The environment
        Life history
        
        Adaptive radiation
        
        2 more items...
- - - - 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
- - - - Population size (N)
        
        Exponential growth
        
        J-shaped curve
        
        Unlimited resources
        
        Logistic growth
        
        S-shaped curve
        
        Typical of a population that
      - Reaching carrying capacity
        
        Overshoot K
        Result in die off
        
        Growth models
        
        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
        
        Model details for population growth
        
        Exponential growth
        dN/dt = rN
        Logistic growth
        dN/dt =
        rN(1-N/K)
        
        r- vs K- selected species
        
        r-selected
        
        Grow exponentially
        
        Disturbed areas
        
        Weedy
        
        Annuals
        
        Little investment in defense
        
        Many, small fruits
        
        K-selected
        
        Fluctuate around carrying capacity
        
        Fairly stable habitats
        Perennials
- - - - 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.
      - Life table practice, G
        
        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
        
        Life table practice, r
        
        Calculate the intrinsic growth rate (r)
        
        Calculated by taking the natural log of the net reproductive rate divided by the mean generation time.
        
        Survivorship curves and age structure
        
        How long did individuals survive
        
        Visual representation of survivorship
        
        Type I, typical of K-selected species
        
        Poa annua survivorship curve
        
        Survivorship curves are plotted logarithmically
        
        Take survivorship (lx) and multiply by 1000
        
        Take the log10 of this value
        
        Plot against age to produce a figure
- - - - Range of interactions
        
        Beneficial interactions +
        
        Negative interaction -
        
        Facilitation (+/+)
        
        Negative interaction -
        
        Facilitation (+/+)
        
        Commensalism (0/+)
        Benefits one, neutral to the other
        
        Amensalism (0/-)
        Negative to one & neutral to other
        
        Competition (-/-)
        
        Both are negatively impacted
        -Predation (+/-)
        Herbivory
      - Predator-prey interactions
        
        Predator
        
        P
        
        Negative impact on prey
        
        Positively impacted by prey
        
        Prey
        
        N
        
        Positive impact on predator
        
        Negatively impacted by predator
        
        Growth models
        
        r = intrinsic growth rate
        
        N = population size
        
        K = carrying capacity
        
        dN/dt = population change over time
        
        Exponential growth
        
        Logistic growth
        
        Predator-prey cycling
        
        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
        
        Lotka-Volterra models
        
        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
        
        LV Practice
        
        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