PCE - 7 Flashcards
what is a trophic cascade?
- an ecological phenomenon triggered by the addition or removal of top predators and involving reciprocal changes in the relative populations of predator and prey through a food chain, which often results in dramatic changes in ecosystem structure
whats the difference between microparasites and macroparasites?
Microparasites do “multiply” in their definitive host so reproduction leads to an increase in the number of parasiteswithin the host and macroparasites do not “multiply” in their definitive host so reproduction occurs, but the host does not end up with more parasites.
(more than one host)
how do parasitoids kill?
Parasitoid larvae, injected into or laid upon the
host, feed exclusively on the body of another
arthropod, eventually killing it. They are obligate killers
but it takes time
what are the 2 major types of transmission pathway?
Vertical transmission - transmission between generations from parent to offspring.
Horizontal transmission - transmission within one generation between unrelated individuals - direct contact
what are the non sexual routes of horizontal transmission (ordinarily infectious diseases OIDs)?
- Aerial transmission (common cold)
- Waterborne transmission (e.g. bacteria such as
Cholera) - Soil borne - with or without long-lived resting
stages - Vector transmission (e.g. malaria)
what affects the differences between transmission modes?
Contact number, contact rates and
population size/density
what are the 3 different transmission modes?
1) OIDs
2) STDs
3) VTDs
describe how host density dependent diseases are a negative feedback cycle?
The more hosts The more contacts The more transmission The more host death Less Contacts….
what is the difference between aerielly transmitted diseases and sexually transmitted diseases?
sexually transmitted diseases are frequency dependent not density
how does density affect vector transmitted diseases?
- Number of contacts first increases with density
- But at high density, if vector population is “fixed”,
then the number of vectors per host falls
what is a mutualism?
symbiosis which is beneficial to both organisms involved.
describe micorrhizza mutualism?
- symbiotic relationship between a fungus and the roots of a vascular host plant
- Sugar from Photosynthetic plants
- N and P to plant from fungal decomposition
what is the mutualistic relationship between ants and trees?
- Ants Protect Trees from Grazing Herbivores
- Trees produce sugars for Ants
what is the problem with current management of honey bees and wild pollinators?
we are currently only managing bee pollinators when it is actually best for the fruit set to be managing both
describe the predator - resource relationship in trophic cascades?
when predators eat prey that means there is less prey eating the resource and therefore the resource abundance increases
describe the experiment on plant biomass using spiders
- they showed that the addition of grasshoppers (prey) meant a decrease in the plant bio mass (resource)
- they then added spiders (predator) to the experiment and saw an increase in biomass from when it was just hoppers
- they also added glued spiders which showed the same affect on the biomass - showing possible fear interactions between predator and prey to also have an affect on biomass
what does SIR stand for?
susceptible , infected, recovered/ resistance
describe the equation for disease modelling?
R0 = N(B/r)
Beta = transmission rate
r = recovery rate
transmission rate / recovery rate - affects the size of R0 and therefore the severity of the disease on reproductive rate
- R0 tells you the average number of people who will catch a disease from one contagious person
- R0 specifically applies to a population of people that was
previously free of infection and has not yet been vaccinated
