What is syngamy?
fusion of gametes
What is amphimixis?
syngamy between parents
What is automixis?
syngamy with same parent
single female produces haploid gametes that unite
What is Muller’s Ratchet?
sex purges deleterious mutations
What is the Vicar of Bray?
sexual recombination increases rate of adaptive evolution by readily bringing together advantageous alleles
What is the bet-hedging model for environmental heterogeneity? (aka best man hypothesis)
When environments are temporally heterogeneous, progeny diversity is highly adaptive
aka: asexual progeny are better in one environment but environments are diverse, so its not always helpful
What is the tangled bank hypothesis?
environments that are spatially heterogeneous, progeny diversity is highly adaptive
asexual do better in one standard environment, not spatially variable ones
What are Koch’s postulates?
- microorganism must be abundant in all diseased organisms but not in healthy ones
- microorganism must be isolated from diseased organism and grown in culture
- cultured microorganism should cause disease when introduced into healthy organism
- microorganism must be re-isolated and re-cultured from newly diseased organism
what are three problems with Koch’s postulates?
- many pathogens are un-culturable
- asymptomatic hosts
- ethical constraint in human disease
Who was John Snow?
mapped distribution of cholera in London and traced source to water pump
What is CCS?
critical community size
minimum size of closed population within a pathogen can persist indefinitely
CCS= k/T*(R0-1)
Define the terms in the CCS equation
CCS = k/T*(R0-1)
k = disease/population constant
T = average duration of infectious period
As T or R0 increase, CCS shrinks
What is competitive release?
parasite induced mortality or morbidity can free up resources for others
What is parasite mediated competition?
parasite directly reduces host fitness which indirectly releasees competitors from competition
What is the keystone effect?
if a host species that is the superior interspecific competitor is more vulnerable to parasitism, then the parasite can allow for coexistence between the species
What is parasite facilitated invasion resistance?
species moves to new range and gains a native parasite which is has no coevolutionary history with. the native species is more resistant to the parasite
Two outcomes:
1. invader dies from pathogen and disappears
2. invader immune but reduces pathogen on resident and is outcompeted (dilution effect)
What are two caveats of the enemy release hypothesis?
- assumes all parasites do equal harm
- parasite-facilitated enemy release hypothesis is independent of parasite abundances/diversity across the populations
What are some parasite traits that can facilitate host extinctions?
high likelihood: generalist parasites, sexual transmission
low likelihood: direct contact (density dependent)
What are some ecological conditions that facilitate parasite-associated extinctions?
habitat disturbance
reduced biodiversity
infection of keystone species
invasive species
