Predation, parasitism, disease

Question 1

Predation/carnivory:

Answer 1

Prey is killed, usually
* Predator generally larger than prey
* Multiple prey individuals per predator

Question 2

Grazing/herbivory:

Answer 2

Plant survives, usually

Question 3

Parasitism/disease:

Answer 3

Host may or may not survive
* Host generally larger than parasite
* Multiple parasites per host

Question 4

Brood parasites

Answer 4

Some birds lay eggs in
the nests of other bird
species, avoiding the
costs of parental care
* Often involves brood
mimicry, in which
parasite eggs evolve to
resemble host eggs

Question 5

But cycles in nature are unusual

Answer 5

Lynx-hare cycles are not simple Lotka-
Volterra predator-prey cycles
* Additional factors probably include:
* Heavy browsing degrades quality of plant food
available to hares—hares may also be cycling
with food plants
* Social stresses in overcrowded hare populations
* Subject of ongoing research
* Most natural cycles have complex causes

Question 6

Antagonistic co-evolution

Answer 6

Coevolution =
reciprocal adaptation
* Prey evolve defenses;
predators evolve
counter-adaptations to
overcome defenses
* Frequently described
as an “arms race”
* Key to the “Red Queen
hypothesis”

Question 7

Life-dinner principle

Answer 7

(unequal selection pressures) one out races the other, can have an effect of extinction

Question 8

Diverse “victim” defenses, often
inducible (turned on in response to
threats or attacks)

Answer 8

Prey morphology,
chemistry, behaviour
* Plant secondary
chemicals
* Human immune
system
* Daphnia ‘helmets’

Question 9

Predation and community structure

Answer 9

Competition tends to
decrease biodiversity;
superior competitors
exclude inferior
competitors
* What about predation?
How does predation affect
species diversity in a
community?
* Classic example is Paine’s
Pisaster (sea star)
experiment in the rocky
intertidal
Robert Paine

Question 10

Pisaster and mussels

Answer 10

Pisaster predation prevents mussels from competitively
excluding other species in rocky intertidal communities,
maintains biodiversity

Question 11

Predators and parasites also
influence biological invasions

Answer 11

Invasive species achieve high population
sizes and have negative effects on
communities they invade

Question 12

Enemy release hypothesis

Answer 12

Invaders’ impacts
result from having fewer natural enemies
(predators, parasites, or pathogens) in their
new range, compared to their native range

Question 13

direct life cycle

Answer 13

Some parasites have a single host species

Question 14

complex life cycle

Answer 14

Many parasites require two or more host species
to complete their life cycle

Question 15

vectors

Answer 15

are hosts that transport parasites to their
next host

Question 16

zoonotic

Answer 16

(diseases
transferred between animals and humans), we
often refer to other host species as reservoirs

Question 17

Dilution effect

Answer 17

for diseases that infect many hosts,
host diversity can “dilute” disease risk to humans
or animals

Question 18

Amplification effect:

Answer 18

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