Final Flashcards
What do the differences in reproductive success lead to?
Differences in sex allocation and sexual selection
Isogamy
Gametes of same size
Anisogamy and what does it result in
Gametes of different size. Leads to differential investment in reproduction
What limits female and male RS
Female RS is limited by the number of eggs produced while male RS is limited by the number of eggs fertilized
What simplifying assumptions does Fisher’s 1:1 sex ratio make
large population, random mating, external mating, and no paternal care
Shaw-Mohler Theorem
For a mutant with a different sex allocation than the resident population to invade, its total fitness must be greater than the residents’
Explain the viviparous mite’s sex allocation
has one son and ~20 daughters in which the son fertilizes the eggs of sisters, once eggs hatch, they eat mother until she bursts and male dies before leaving the mother. Only need one male to fertilize daughters thus, want maximum number of females as possible
Explain the correlation between mormon crickets and OSR
Males produce a spermatophore that contains sperm but also a large amount of protein making it very expensive thus, the limiting factor. In many insects, females store the sperm of different partners. Males evolved to ensure that females cannot use sperm of other males such as a penis that scrapes the sperm out of other males or that packs the sperm of other males into the corners
Operational Sex Ratio (OSR)
ratio of sexully competing males to sexually receptive females (the less of one sex, the more intense competition is and thus selection for better secondary sex characteristics)
Explain intersexual selection in drosophila
More that males mate, the more offspring they have but females can only have as many offspring as the number of eggs they produce. When females mate more often they have shorter life spans because males have toxic seminal fluid to increase the number of eggs they fertilize since females optimize the rate of egg laying thus, if they die sooner will have more offspring at one time
Explain the effect of male competition on intersexual selection in drosophila
Females came from a control population while males were allowed to evolve. Led to increased male fitness and sperm defense such that female survival decreased due to increased toxicity in sperm
Explain the effect of monogomy on intersexual selection in drosophila
males typically have higher genetic representation since they can mate multiple times but when taken away their seminal fluid becomes less toxic thus, female reproduction, surivival, and fecundity was higher
What does sexual selection lead to
traits that have no function other than to attract mates
Fisher’s runaway hypothesis
assuming there is a female preference for a trait, she will mate with males that have that trait and her daughters will carry the gene for the preference and her sons will have the trait
When does natural selection occur
When there is heritable variation among replicating units and there is non-random survival and reproduction is associated with the variable phenotype
On what levels can natural selection occur
populations of replicating units (genes and organelles), individual organisms, populations of population of individuals, and groups of species/lineages
At what levels of selection can conflict occur
- Traits can increase the fitness of genes/organelles but also decrease the fitness of the organsim
- Traits that benefit an entire population may not be the most for the individuals in the population
What level of selection is the most powerful and why
individual since there tends to be higher inheritability and faster reproduction
What characteristics allow selection to operate efficiently
large population size, high level of variation, strong heritable components to traits, and short generation time
What are the two types of selfish genes and how common are they
Segregation distorters (when one allele is overrepresented in gametes) and transposable elements (sequences of DNA that can change its position)
How do segregation distorters work and explain an example in drosophila
Sperm created from a diploid (aA) is unequally distributed. In flies there is dominant gene that decreased fertility in males by 50% thus, on the genic level is very hard to get rid of but on the individual level is not helpful as it decreases fertility
What are the types of transposable elements work
- Type 1: copy and paste genes into the genome
- Type 2: cut and paste DNA (can be sloppy and take other parts of DNA wtih it, or leave some behind)
- Both can be mutagenic if inserted in the middle of protein coding regions
At what levels does organelle selection occur
- cells in a multicellular organism
- mitochondrial DNA
What is the possible condition if the mitochondrial DNA of A and a replicate at the same rate and equally distributed
Normal conditions
What are the possible conditions when mitochondrial DNA of A replicates faster than a
Selection is occuring and if A contributes more to the cell’s fitness then there is no genomic conflict between the two levels unless a is more fit for the cell than A
What are the possible conditions when mitochondrial DNA A and a replicate at the same rate bt are unequally distributed
Selection is occuring and if A contributes more to the cell’s fitness then there is no genomic conflict unless a contributes more to the cell’s fitness
Explain the yeast and organelle selection example
Petitie mutants can replicate faster yet are a fitness disadvantage compared to wild types because they can’t respire. Populations of varying size were allowed to grow to 150 generations. Smaller populations moved towards fixation for petitie mutant DNA since genetic drift was a dominant evolution force, medium sized populations did not fix towards any extreme, and large sized populations ended up with no mutant cells since there was strong selection among individuals
Weissmanist organism
Separation between the soma and germline thus, there is selection among cells in the body but will not be passed on
Clonal interference
In a population with no recombination, when beneficial mutations occur on different genetic backgrounds, they compete with each other
What is needed for population selection
Small groups so genetic drift is important, rapid group generation time, lots of variability among groups, and very strong group selection
Explain the levels of selection between house mice and the t-haplotype
- Genic selection: heterozygous sperm is skewed towards the t-haplotype while heterozygous females produce a 1:1 ration
- Group selection: mice reproduce via harems thus, these small groups are more susceptible to genetic drift and a homozygous mutant would go towards extinction more easily but could be recolonized by fertile males that are heterozygous or homozygous wild type
- Individual selection: males homozygous for t are sterile and populations are typically 60-90% mutants
Explain the levels of selection between myxomatosis and rabbits
Replication rate of virus within rabbits is like individual selection. Faster replication rate leads to faster virulence thus, selection on an individual level favors increased virulence. Found that wild populations of rabbits built resistance to the original strain
Transmission rate of virus is like group selection. Selection favors stains that allow rabbits to live long enough to infect many other rabbits. Found that when wild strains of the virus were injected into lab rabbits, the virus became less virulent
Prezygotic isolation
Reproductive barriers that occur before fertilization
What is temporal isolation and what is an example
barrier due to timing in reproduction. 2 species of coral. Gametes are relesased into the water for ~30 minutes for one species then other species releases gametes an hour afterwards
What is pollinator isolation and give an example
barrier due to pollinator preference. Pollinators are loyal to flowers even if they both exist in the same environment. Hybrids of two flowers are viable but attracted only one of two pollinators not both
Postzygotic isolation and example
reproductive barriers that occur after fertilization. Horse and donkey have viable offspring but is sterile
Bateson-Dobzhansky-Muller incompatabilities
when an ancestral population diverges so much that the ancestors are not able to breed
Biological Species Concept
Species are groups of interbreeding populations that are reproductively isolated from other such groups
What are the problems with the BSC
- Difficult to know if species that are physically isolated are also reproductively isolated
- Especially hard to apply to bacteria and archaea since they don’t reproduce sexually so no way to find divergence patterns
- Difficult to apply to plant species that hybridize so easily
Explain how the BSC was used to determine Cichlid species
Two species produce viable offspring and show preference for own species but under certain light, females of both species show preference for blue males thus, they are not reproductively isolated
Phylogenetic species concept
Species are groups that have unique, derived traits; important criterion is monophyly
What are the problems with the PSC
- Lack of genetics on many animals thus, hard to determine where closely related speceis diverge
- Hard to determine what trait differences are considered “statistically significant”
- If applied, number of species would more than double
How was the PSC used to determine species of elephants
Originally thought that there were 2 species. Scientists discovered that elephants in Africa had vastsly different habitats and rarely interacted. PSC showed that there are three types of elephants
Morphospecies concept
looks at the morphological differences among populations, predominantely used by paleontologists
What problems are there with the morphospecies concept
- defining morphological differences can be subjective and idiosyncratic
- many relevant traits are not recorded in fossils (soft tissue, behaviors…)
Explain red wolf conservation
- Red wolves resemble coyotes suggesting that coyotes and red wolves hybridize but when captured had no coyote traits.
- BSC: red wolf could be the result of hybridization between a coyote and gray wolf thus, is not a species
- Morphospecies concept: prior to hunts starting on wolves, red wolves had distinct skull and dental traits that were intermediate between the gray wolf and coyote. after hunting, red wolves are much more similar to coyotes likely due to hybridization because of habitat overlap thus, red wolf is a species
- PSC: DNA from before hunts, wolves had no distinct differences between red wolf and coyote thus, is not a species
What are the stages of speciation
Isolation of populations, divergence between populations, and reproductive isolation of populations
What are the types of physical isolation
- dispersal and colonization
- Vicariance: splitting of population into two or more isolated ranges and reduction of gene flow between them
What leads to genetic isolation
Changes in chromosomes that lead to incompatabilities between gametes with different chromosome numbers (polyploidy)
What causes to polyploidy
autopolyploid: chromosomes originate from same ancestral species (genome doubles)
Allopolyploids: chromosomes come from hybridization between different species
What are the mechanisms of divergence
- Genetic drift: causes random fixation and loss of alleles
- Natural selection: major mechanism of speciation when speciation involves occupation of novel environments
Sympatric speciation
Speciation when groups occupy same location when two conditions are met:
* Strong selection for divergence
* Mate choice correlated with factor that is promoting divergence
* Behavioral isolation
parapatric speciation
Speciation when groups are located adjacent to each other when strong selection causes gene frequencies to diverge along a gradient
Fossil
Any trace left behind by an organism
How old is the Earth and how do we know
4.6 billion years. Know because rubidium had the longest half life
What are the four ways to generate a fossil
Compression and impression, permineralized, casts and molds, and unaltered remains
How does compression and impression lead to fossils
organisms are buried in sediment before it decomposes. Pressure of sediment forms an impression
How does permineralization lead to fossils
organisms are buried in sediment and dissolved minerals in organism precipiate in the cells
How do casts and molds lead to fossils
organism decay or dissolves, leaves space, and new material takes up space
How do unaltered remains become fossils
when weathering, scavenging, and decomposition are minor (permafrost, tar pits…)
What affects the possibility of fossilization
Specimen durability, burial, and lack of oxygen (organisms from particular habitats and show particular behaviors are more likely to be fossilized)
What are the weaknesses of the fossil record
- Only have records of animals from certain geographical locations (wet and anaerobic habitats)
- Almost 70% of animals lack hard structures thus, most fossils are marine
- Fossils can be lost wehn Earth’s crust are recycled
What are the strengths of the fossil record
- no other way to learn so far into the past
- can identify major evolutionary events in history of life
- can be used to learn about natural history, behavior, and appearance of extinct organisms
When was the origin of life
3,900 million years ago
When was the origin of eukaryotes and sex
2,500 million years ago
When was the origin of multicellularity
1,000 million years ago
When and what was the cambrian explosion
Origination of animals that we see today, 540 million years ago likely happened as a result of changing ecology of ocean
How long ago did the extinction of dinosaurs and ammonites happen
65 million years ago during the Cretaceous period
What are the big 5 mass extinctions
- End-Ordovician (440 mya)
- Late-Devonian (365 mya)
- End-Permian (250 mya)
- End- Triassic (215 mya)
- Cretaceous-Tertiary (65 mya)
Define life
- ability to store and transmit information (hereditary and genotype)
- Ability to express that information
Panspermia hypothesis
life originated elsewhere in another solar system and traveled here
What is the RNA world and what evidence is there for it
primordial form of life was an RNA-based system that later evolved into what we see today
Evidence
* Ability to express information (phenotype)
* Ability to store and transmit information (genotype)
* Ribozymes (allow RNA to act as an enzyme)
What are the four postulates of natural selection
- populations contain variation
- some of that variation is heritable
- populations produce more offspring than can survive
- survival and reproduction are non-random
Evolution
Change in gene frequencies
Adaptation
condition of a trait that conveys a reproductive advantage
What is genetic drift
the random, non-representative sampling of alleles from a population
What are the effects of genetic drift
random fixation of alleles (esp in small populations) and loss of heterozygosity
What causes genetic variation
mutations, recombination, and migration
Heterochrony
tweaking the timing and rate of development (changing when and where genes are turned on)
Heterotopy
Tweaking the location of expression of developmental genes; generally refers to changes in the cells/tissues in which gene activation or other developmentla events occur
What is an evolutionary stable strategy
a strategy that when adopted by most individuals of a population cannot be invaded by another strategy that is initially rare
What causes altruism to evolve
if the coefficient of relatedness between the actor and recipient is sufficiently large
What ensures that there are no cheaters in altruism
- cheaters should not be able to get away from retaliation
- cooperators should be able to recognize each other
- probability of two cooperating individuals interacting repeatedly must be high
sex
coming together of different genomes in one individual
Recombination
production of new combinations of genes
What are the costs of sex
Time and energy spent locating mate, competing for mate, exposure to parasites and STDs, spread of selfish genes, breaking up of advantageous allele combos, two-fold cost of sex
What is the two-fold cost of sex?
If females produce two offspring every generation then an asexual female can give rise to two females (clones) but a sexual female will likely give rise to a sexual male and female thus, the sexual female does not benefit as much compared to the asexual female
How long ago was the extinction of 83% of marine genera
250 million years ago during the permian period
