Lecture 7 - Trophic Cascades & Disease

Question 1

what is a trophic cascade

Answer 1

positive indirect relationship between predator and resource

predators suppress prey

Question 2

can trophic cascades be behaviourally mediated

Answer 2

yes, if a sense of risk = behaviour and habitat use changes

e.g. glued mouth spiders altered nymph time budget and activity time

Question 3

characteristics of microparaistes

Answer 3

multiply IN host
reproduction = greater no. parasites within host
e.g. malaria, influenza

Question 4

characteristics of macroparaistes

Answer 4

don’t multiply in host
reproduction doesn’t mean more parasites on host
e.g. ticks, nematodes

Question 5

what are parasitoids

Answer 5

larvae injected/laid on host
feed exclusively on another arthropod
obligate killers

Question 6

vertical transmission

Answer 6

between generations, parent to offspring

Question 7

horizontal transmission

Answer 7

within generations, unrelated indvs

Question 8

what forms of contact are there

Answer 8

sexual, aerial, waterborne, soil borne, vector

Question 9

aerial transmission

Answer 9

random contact, then rain of infection

host density dependent, creates negative feedback

Question 10

sexual transmission

Answer 10

random encounters
frequency dependent
number contacts saturates,

Question 11

vector transmission

Answer 11

contacts increase with density at first

high density, if vector population fixed, vector no. per host falls

Question 12

what is the SIR model of disease

Answer 12

susceptible infected resistant/recovery

Question 13

what is Ro = N (B/r)

Answer 13

tranmission rate/recovery rate (contacts/immune system)
B = transmission
r = recovery/immune sysrem

Question 14

what is Ro

Answer 14

average number of people who will catch a disease from one contagious person
population previously free of infection, not vaccinated