ch19 Flashcards
Genetic Variation
Phenotypic variation - varied expression in same population
Natural selection - select traits become more common (random mutation, non-random selection)
Genetic drift
Change alone shifts phenotype
Change in alleles by chance (due to random event)
Founder effect - few individuals leave population which creates limited gene pool to start (likely carry-over recessive traits)
Gene flow
New alleles enter population
New phenotype in a new generation
Transfer of alleles into or out of population
Individual Genetic variation
Genetic variability - whole gene level variation
Nucleotide variability - molecular variability in DNA
(molecular variation doesn’t equal change phenotype
Non heritable variability - acquired traits cannot be passed down
Source of genetic variation
New (mutant) alleles - neural variation (no observed affect)
Gene number/position - translocation of one gene (small - okay, large - bad)
Rapid reproduction - more prevalent in prokaryotes
Sexual reproduction - shuffling of alleles (crossing over, independent assortment, fertilization)
Population and Genetics
All individuals in one area at one time that may interbreed and exchange genes
Evolution -genes change through genetic variation
Changes compound and new species form
Mircoevolution
“small scale” evolution
Genes + Environment = expressed traits
Hardy-Weinberg Equilibrium
Dominant allele - p
Recessive allele - q
Gene pool -> p+q=1.0
Allelic frequencies ->
p^2 + 2pq + q^2 = 1.0
Non-evolving population - allelic and genotypic frequencies in equilibrium, only follows Mendelian inheritance with random mating in large, sexually reproducing population
Hardy Weinberg equilibrium is true if…
1) No mutations
2) No migration
3) Large gene pool
4) Random mating
5) No selection
Genetic bottleneck
Small fragmented population with limited genetic diversity
(Gene pool is restricted)
Consequences of Genetic Drift
1) Significant in small populations
2) Allele frequency may change at random
3) Loss of genetic variation within a population
4) Harmful alleles may become fixed
Natural Selection
Random variation and non-random selection
three types - Directional, Disruptive, Stabilizing
Absolute fitness
Individuals contribute to gene pool
Relative fitness
Individual contribution relative to all individuals
Genetically fit individuals
Most likely to contribute genes
“survival of the fittest”
Directional Selection
Extreme phenotype is favored
May occur as population adapts
Disruptive Selection
2+ extreme phenotypes favored
Not intermediate
Two phenotypes in same population
Stabilizing Selection
Intermediate form selected
More likely to be carried over
Reduced phenotypic variability
Sexual Selection
Adaptive changes to males and females
Males - higher ability to complete
Females - picky about males
(runaway, differential, dimorphism, intrasexual, intersexual)
Runaway Selection
Extremely favored
Extreme may become bad
Differential sexual selection
Less choosy females and most fit males
Stabilize the population
Sexual dimorphism
Distinct differences between sexes
Size and color are most common differences
helps establish fitness
Intrasexual selection
Individuals within sex compete with one another
Males patrol/protect territory
“psychological” competition prevents physical competition
Intersexual selection
Male choice is noticeable
Chooses individuals with better genes
