Lecture 20: Predation, Parasitism, and Disease

Question 1

Brood mimicry

Answer 1

parasite eggs mimic host eggs (host bird raises other birds young parasite bird avoids costs of parental care) ex. cuckoo

Question 2

Predation/carnivory

Answer 2

• prey is usually killed
• predator is generally larger than prey
• multiple prey individuals per predator

Question 3

parasitism/disease

Answer 3

• host may or may not survive

- multiple parasites per host

Question 4

What is distinctive for for LV models of predator-prey interactions

Answer 4

Coupled, lagged population cycles (pred behind prey)

Question 5

Do we actually see cycles of pred prey populations in real life? Why or why not?

Answer 5

In the lab: cycles have been produced but not sustained. Predator prey in direct coexistence is an unstable interaction.
In real life: lynx and hare most famous cycles (arctic, specialized relationship) but still not as predicted by LV as hares might be cycling with food plants

Most nature cycles have complex causes

Question 6

antagonistic co evolution

Answer 6

reciprocal adaptation

• prey evolve defences, predators evolve counter defences (arms race)
• Red Queen hypothesis

Question 7

Why is there stronger selection of prey than on predators?

Answer 7

Prey are running for their life whereas predators are only running for their dinner (Dawkins 1979)

Question 8

Robert Paine

Answer 8

Studied sea stars, realized some predation can maintain biodiversity if the predator’s main prey is a species that would outcompete other prey
- Predation by sea stars maintain species richness

Question 9

What is the human immune system an example of?

Answer 9

induced defence (adaptive phenotypic plasticity)

Question 10

enemy release hypothesis

Answer 10

invasive species do not bring their own natural predators with them, thus they thrive (to the detriment of native species with nothing to keep them in check)

Question 11

direct life cycle

Answer 11

single host species

Question 12

complex life cycle

Answer 12

require two or more hosts species to complete their life cycle
ex. parasite that causes malaria passes through two hosts; mosquito then human

Question 13

vectors

Answer 13

hosts that transport parasites to their next host

Question 14

Reservoirs

Answer 14

The habitat that an infectious agent normally lives, grows, and multiples

• term usually used often in reference to zoonotic diseases; the other host species that carries a specific disease
  ex. Bats, raccoons, dogs are reservoirs for rabies

Question 15

What can affect parasite abundance and transmission?

Answer 15

distribution, life history traits, host behaviour

Question 16

Dilution effect

Answer 16

for diseases that affect many hosts, host diversity can dilute a disease risk to humans or animals

Question 17

Amplification effect

Answer 17

more host or vector species can support larger populations of disease-causing organisms, increasing risk to humans and animals.

Question 18

Why are amplification and dilution effect mutually exclusive?

Answer 18

One says having more hosts is better while the other says that having more hosts increases risk of disease

Question 19

Example of the Amplification effect

Answer 19

Malaria in schoolchildren in Kenya

- greater species richness of the vector hosts coincided with greater malaria prevalence

Question 20

Where is there more species richness?

Answer 20

Near the equator. It’s a latitudinal gradient.