Parasite Niche, Transmission and Virulence Flashcards
What is a parasite?
A symbiont that gains benefit in terms of nutrients at the expense of it’s hosts
Define ‘ecological niche’
Multidimensional summary of tolerances and requirements of a species
What does the ecological niche consider?
Abiotic factors (eg. temperature, salinity, pollution) and Biotic interactions (eg. predator-prey interactions, competition)
What is the fundamental niche of a species?
Set of resources that it is capable of using in the absence of any interspecific competition
What is the realised niche of a species?
Set of resources that a species actually uses in response to the presence of interspecific competition
Describe the Competitive Exclusion principle
When two species are competing, their realised niches may be too similar, and one of the species will out-compete the other, leading to competitive exclusion
What is resource partitioning?
When two species are competing and have different enough realised niches for them to co-exist then the species exploit different components of the same resource, reducing competition
Give an example of a species that takes part in resource partitioning
Wading birds
Give an example of an ectoparasite
Ticks, lice
What are ectoparasites?
Parasites that live and feed on the surface of their host
Give an example of an endoparasite
Tapeworm, Plamodium
What are endoparasites?
Parasites that live and feed within their host
Who has the bigger reproductive potential, the parasite or the host?
Parasite
What is a degenerative parasite?
Parasite that lacks structures and organs found in other organisms
Give an example of a degenerative parasite
A tapeworm
Lacks digestive system
In what host does the parasite reach sexual maturity?
Definitive Host
What is the intermediate host?
One in which the developmental stages of a parasite’s lifecycle occur
What is the name for a species that plays an active part in the transmission of a parasite?
Vectors
What is virulence, in relation to parasites?
The harm that a parasite causes to a host species
State the two evolutionary stable strategies in relation to transmission and virulence
Low transmission, low virulence
High transmission, high virulence
Why is high virulence, low transmission not an evolutionary stable strategy?
The parasite will not be transmitted sufficiently well to find new hosts and will die out
Why is the high transmission, low virulence strategy not evolutionary stable?
Will be out-competed by a more virulent strain
What transmission/virulence strategy does the common cold, rhinovirus use?
Low transmission, low virulence
What are the three factors that increase transmission rates?
- High Population Density
- Use of Vectors
- Water borne dispersal stages
How does high population density increase transmission rates?
If hosts habitat is overcrowded, increases the chance of transmission by direct contact/ droplets
What is the extended phenotype of a parasite?
When the parasite modifies the hosts behaviour
What are the five categories of modifying host behaviour?
Host foraging Movement Sexual Behaviour Habitat Choice Anti-predator behaviour
What is the advantage of a sexual phase in a parasite?
Produces genetic variation and so allows the rapid evolution needed in the Red Queen’s race between parasite and host
What is an advantage of an asexual phase in a parasite?
Rapid build up of a parasite population for dispersal into the next host
What are the three factors that increase virulence?
- Suppress the host immune system
- Modify the size of the host
- Reduce the host’s reproductive rate
How does suppressing the host immune system increase virulence?
Allows parasites to survive and reproduce in the host without being attacked by the host’s defences
How does modifying the host’s size increase virulence?
Grows much larger so can support the asexual reproduction of more parasites
How does reducing the host’s reproductive rate increase virulence?
More of the host’s energy can be directed to parasite reproduction
What may cause a difference in host infection rates between members of the same population?
Sex
Age
Genotype
Behaviour
