Parasitism, Predation and Grazing Flashcards
How does the prey population grow in the absence of predation?
The population grows exponentially.
What factors affect how predators influence the prey population?
Prey density, predator density and predator hunting efficiency.
What is Holling Type I predator handling efficiency?
A linear increase in feeding with prey density until a maximum is reached i.e. cannot feed any faster.
What is Holling Type II predator handling efficiency?
Consumption increases as density increases but prey handling time becomes the limiting factor.
What is Holling Type III predator handling efficiency?
Sigmoidal relationship between host/prey density and consumption rate. Low prey density results in increased search effort.
What is the SIR model?
Susceptible, infected and recovered. The simplest parasite/pathogen model.
What impacts the proportion in each group of the SIR model?
Infection rate and recovery rate.
What are some of the assumptions in the SIR model?
Closed population with no population growth.
No death in infected population.
Recovered population is either immune, dead or quarantined.
What is R0?
The number of primary infections arising from 1 infected individual in a wholly susceptible population. It is very hard to estimate
What does an R0 value of over 1 mean?
An epidemic can take off - the infected population is going to increase.
What does an R0 value of less than 1 mean?
An epidemic cannot take off - the infected population is going to decrease.
How are parasites distributed in a host population?
In an aggregated distribution; most hosts have just a few parasites, a few hosts have many.
Why are parasites distributed in a certain way?
Host survivorship/fecundity depends on parasite number.
What impacts immune responses to parasites?
Parasite type, parasite location, parasite behaviour and the damage the parasite causes.
How does the immune system and parasite interact?
The parasite can suppress the immune system or promote the immune system - sometimes this is advantageous.
Define predation.
Any interaction between organisms in which an organism (predator) consumes all or part of another organism (prey).
What are some prey adaptations in response to predation?
Toxins, cryptic colouration, mimicry, weaponry and herding behaviour.
What causes the cyclic oscillations of predator-prey populations?
Predators eat the prey so prey numbers drop.
Predators starve and decline in number.
With fewer predators, prey population increases.
With more prey, predator population increases.
What is a keystone species?
A strongly interacting species that has a large impact on species diversity and competition in its ecosystem. Often predators.
What is the escape mechanism for reducing herbivory?
Developing traits that reduce the likelihood of discovery by a herbivore eg size or dispersal.
What is the tolerance mechanism for reducing herbivory?
Developing traits that reduce the negative impacts of herbivory eg compensatory growth and resource allocation.
What is the defence/resistance mechanism for reducing herbivory?
Developing traits that affect herbivore behaviour and reduce herbivore performance.
What are constitutive defences?
Defences produced and present in the plant irrespective of attack.
What are induced defences?
Defences produced by and present in the plant in response to attack. A form of phenotypic plasticity.
What are some examples of structural defences?
Thorns, spines, prickles, trichomes and sclerophylly.
What are secondary metabolites?
Compounds produced that appear to have no direct function in photosynthesis, growth or respiration.
What are some functions of secondary metabolites in plants?
Providing protection to the primary metabolism from herbivores.
Attracting pollinators.
Provide advantages in plant-plant competition.
What are some examples of chemical defences?
Alkaloids, terpenoids, steroids, phenolic compounds, cyanogenic compounds and glucosinolates.
What can lead to induced defence reactions?
Abiotic stress conditions (eg drought), grazing or volatile compounds from neighbouring damaged plants (inter + intraspecific).
What is the Pest Pressure Hypothesis?
High species abundance leads to increased vulnerability to predators. Where a plant species is common, you get a build-up of its specific herbivores.
What is the Competition Pressure Hypothesis?
Intense competition leads to exclusion of less competitive species. Reduced competition results in greater species diversity. Suppression of competitive species increases diversity.
