Midterm Review Flashcards
How fast can artificial selection go?
depends on:
- genes
- genetic variation available
- how much of the phenotype is envionmental factors
- deleterious consequences
How many kingdoms are there?
Linnaeus proposed just two kingdoms - plants and animals
- Five kingdom system
- domains
What are the three domains?
- Bacteria
- Archaea
- Eukarya
Genetic Correlation
selection favouring alleles for one trait causes a correlated bu suboptimal change in an allele for another trait
Historical Constraints
present variation biases future possibilities - species evolve from ancesters
Formal Constraints
laws of physics
Temporal Constraints
Evolution occurs by mutation and it takes time for a series of useful mutations to occur - small phenotypic effect
Genetic Correlation
changing one feature often affects multiple features ex. reduction in jaw size led to suboptimal tooth arrangement in humans.
Fitness Trade-offs
- compromise between traits in terms of how the traits are adapted for the environment. ex. brain size and pelvis
COMPROMISE
The Hardy Weinberg principle
A null hypothesis that predicts what genotype frequencies should be given known allele frequencies.
Allele frequency:
the frequency of each allele
*two pop. with the same allele frequencies can have different genotype frequencies. ex moths
Genotype frequency:
the frequency of various allele populations
Natural selection
increases or decreases the frequency of certain alleles
Genetic Drift
Causes allele frequencies to change randomly (stochastically) over time
Gene Flow
(migration) introduces alleles from another population
- homogenize gene frequencies
- tends to reduce genetic difference b/w pop.
Mutation
Modifies allele frequencies by continually introducing new alleles, even deleterious ones.
Gene pool
All of the gametes produced in each generation go into a single group and then combine
The Hardy Weinberg principles that must hold true:
- no natural selection on fitness
- no genetic drift
- no gene flow
- no mutation
- no biased mating
HLA and heterozygosity
T-shirt smelling experiment
Is the HLA locus of Humans in Hardy-Weinberg Equilibrium?
- mutation, migration, and genetic drift are negligible in this case
1) mating is biases with respect to the HLA genotype
2) heterozygous individuals have higher fitness
Heterozygous advantage:
Is a pattern of natural selection in which heterozygous individuals have higher fitness than homozygous individuals do. Must be co-dominant. ex. sickle cell anemia
Directional Selection
When an extreme phenotype is favored by natural selection. Type of natural selection. ex. increased body size in swallow pop.
Stabalizing Selection
Reduces the amount of variation in a trait. ex. Very large and very small newborns are less likely to survive.
Disruptive Selection
increases the amount of variation in a trait ex. black bellied seedcrackers with either long or short beak. Castes of ants
Negative Frequency Dependent Selection
Fitness is highest in rare phenotypes. ex. snakes
Frequency dependent selection
fitness is highest in common phenotypes
Impact of selection on phenotypic variance and allelic diversity
Different mechanisms can increase or decrease variance and diversity but most decrease.
Genetic Drift
is any change in allele frequncies in a population due to chance
frequencies drift up and down randomly
unbiased with respect to fitness
Indian Javan Rhino
Genetic drift
Founder effect
Large population separates into a small isolated population, diversity is lost
Bottlenecks
Populations go through a bottleneck. The longer and more sever the bottleneck the more diversity lost ex, cheetah can share skin grafts they are so genetically similar
What is a population?
Groups of individuals with diff. allele frequencies
Natural selection and genetic diversity
- cannot increase (could decrease) number of alleles in a population but it can increase (usually reduces) the diversity of alleles by influencing the frequency of pre-existing variation
- All other mechanisms decrease diversity
Only mechanism to create new alleles
Mutation
polymorphism
existing variation
Nonrandom Mating
May not be random with respect to any particular gene in question
Examples of biased mating
- inbreeding
- sexual selection
(violate hardy-weinberg)
Inbreeding
- increases the frequency of homozygotes and reduces the frequency of heterozygotes in each generation.
- does not change allele frequencies but does change genotype frequencies (increases homozygosity)
Inbreeding Depression
a decline in average fitness that takes place when homozygosity increases and heterozygosity decreases in a population
Causes of inbreeding depression?
- many deleterious mutations are recessive
- at some loci there is an advantage to being heterozygous
- Inbreeding increases homozygosity resulting in decreased fitness
Advantages of inbreeding?
Purges your genetic load and removes deleterious alleles from the pop. Observed in plants.
Allele frequency inbreeding vs inbreeding depression
Inbreeding: does not change allele frequencies it only changes genotype frequencies
Inbreeding depression: does not change allele frequencies either because homozygous deleterious recessives are more common in inbred individuals or because beneficial heterozygous genotypes are less common in inbred individuals
Sexual selection
occurs when individuals within a population differ in their ability to attract mates. Favours those who can attract mates.
The fundamental asymmetry of sex
-females invest more into their offspring than males therefore females should be choosy about mates
Sexual Cannibalism
- Nutritional benefits
- mechanism of rejection
- mistaken identity
- prevent male monopolization
sexual dimorphism
trait that differs between males and females of the same species
How fast can artificial selection go?
depends on:
- genes
- genetic variation available
- how much of the phenotype is envionmental factors
- deleterious consequences
Genetic drift
more pronounced in small populations than large ones
-Great concern to conservation biologists because endangered species are especially susceptible
How many kingdoms are there?
Linnaeus proposed just two kingdoms - plants and animals
- Five kingdom system
- domains
What are the three domains?
- Bacteria
- Archaea
- Eukarya
Genetic Correlation
selection favouring alleles for one trait causes a correlated bu suboptimal change in an allele for another trait
Historical Constraints
present variation biases future possibilities - species evolve from ancesters
Formal Constraints
laws of physics
Temporal Constraints
Evolution occurs by mutation and it takes time for a series of useful mutations to occur - small phenotypic effect
Genetic Correlation
changing one feature often affects multiple features ex. reduction in jaw size led to suboptimal tooth arrangement in humans.
Fitness Trade-offs
- compromise between traits in terms of how the traits are adapted for the environment. ex. brain size and pelvis
COMPROMISE
The Hardy Weinberg principle
A null hypothesis that predicts what genotype frequencies should be given known allele frequencies.
Allele frequency:
the frequency of each allele
*two pop. with the same allele frequencies can have different genotype frequencies. ex moths
Genotype frequency:
the frequency of various allele populations
Natural selection
increases or decreases the frequency of certain alleles
Genetic Drift
Causes allele frequencies to change randomly (stochastically) over time
Gene Flow
(migration) introduces alleles from another population
- homogenize gene frequencies
- tends to reduce genetic difference b/w pop.
Mutation
Modifies allele frequencies by continually introducing new alleles, even deleterious ones.
Gene pool
All of the gametes produced in each generation go into a single group and then combine
The Hardy Weinberg principles that must hold true:
- no natural selection on fitness
- no genetic drift
- no gene flow
- no mutation
- no biased mating
HLA and heterozygosity
T-shirt smelling experiment
Is the HLA locus of Humans in Hardy-Weinberg Equilibrium?
- mutation, migration, and genetic drift are negligible in this case
1) mating is biases with respect to the HLA genotype
2) heterozygous individuals have higher fitness
Heterozygous advantage:
Is a pattern of natural selection in which heterozygous individuals have higher fitness than homozygous individuals do. Must be co-dominant. ex. sickle cell anemia
Directional Selection
When an extreme phenotype is favored by natural selection. Type of natural selection. ex. increased body size in swallow pop.
Stabalizing Selection
Reduces the amount of variation in a trait. ex. Very large and very small newborns are less likely to survive.
Disruptive Selection
increases the amount of variation in a trait ex. black bellied seedcrackers with either long or short beak. Castes of ants
Negative Frequency Dependent Selection
Fitness is highest in rare phenotypes. ex. snakes
Frequency dependent selection
fitness is highest in common phenotypes
Impact of selection on phenotypic variance and allelic diversity
Different mechanisms can increase or decrease variance and diversity but most decrease.
What is a population?
Groups of individuals with diff. allele frequencies
Natural selection and genetic diversity
- cannot increase (could decrease) number of alleles in a population but it can increase (usually reduces) the diversity of alleles by influencing the frequency of pre-existing variation
- All other mechanisms decrease diversity
Only mechanism to create new alleles
Mutation
polymorphism
existing variation
Nonrandom Mating
May not be random with respect to any particular gene in question
Examples of biased mating
- inbreeding
- sexual selection
(violate hardy-weinberg)
Inbreeding
- increases the frequency of homozygotes and reduces the frequency of heterozygotes in each generation.
- does not change allele frequencies but does change genotype frequencies (increases homozygosity)
Inbreeding Depression
a decline in average fitness that takes place when homozygosity increases and heterozygosity decreases in a population
Causes of inbreeding depression?
- many deleterious mutations are recessive
- at some loci there is an advantage to being heterozygous
- Inbreeding increases homozygosity resulting in decreased fitness
Advantages of inbreeding?
Purges your genetic load and removes deleterious alleles from the pop. Observed in plants.
Allele frequency inbreeding vs inbreeding depression
Inbreeding: does not change allele frequencies it only changes genotype frequencies
Inbreeding depression: does not change allele frequencies either because homozygous deleterious recessives are more common in inbred individuals or because beneficial heterozygous genotypes are less common in inbred individuals
Sexual selection
occurs when individuals within a population differ in their ability to attract mates. Favours those who can attract mates.
The fundamental asymmetry of sex
-females invest more into their offspring than males therefore females should be choosy about mates
Sexual Cannibalism
- Nutritional benefits
- mechanism of rejection
- mistaken identity
- prevent male monopolization
sexual dimorphism
trait that differs between males and females of the same species