Lec 23- Mutualism and Parasitism

Question 1

mutualism

Answer 1

++
- symbiotic
- plants: benefit from mycorrhizae through increased nutrient uptake in soil (+) - vital in poor nutrient or arid soil

Question 2

commensalism

Answer 2

0+
- barnacles and whales
- barnacles: benefit from substrate and dispersal provided by whales (+)
- whales: no benefit and no harm (0) - facilitate the dispersal of barnacles

Question 3

exploitation

Answer 3

-+

Question 4

mycorrhizae

Answer 4

crop and forest productivity
ecosystem functioning

Question 5

insects

Answer 5

crop pollination
honey production
pollinator networks

Question 6

parasites

Answer 6

diseases

Question 7

parasitism

Answer 7

beneficial to one and detrimental to other (exploitation)
- tick: benefit by feeding on blood in animals (+) - Lyme disease
- host: harmed through blood removal and disease risk

Question 8

parasitic relationship

Answer 8

parasites engage with various organismal groups
- very host-specific
- all organisms encounter parasites throughout life
- mistletoes, tongue-eating lice, tapeworms, ticks

Question 9

parasite-host relationship

Answer 9

share characteristics with predator-prey and herbivore-plant relationships (exploitative interactions)
- plant fungal parasite and herbivore reducing plant biomass
- parasite forms an intricate and long-term relationship with host

Question 10

symbiosis

Answer 10

intricate and long-term living of 2 organisms
- Heinrich Anton de Bary
- commensalism. mutualism, parasitism
- very species-specific
- gradients and contingent on env. factors

Question 11

can parasites alter behavior of host to their favor?

Answer 11

yes
- European starling (host)
- isopods
- thorny-head parasitic worms Plagiorhynchus
Crustacean isopod = Plagiorhynchus intermediate host (parasite grows here but doesn’t reach sexual maturity)
European starling = Plagiorhynchus definite/primary host (parasite reaches adult stage and sexual maturity)

Question 12

Red Queen hypothesis

Answer 12

• species have to evolve to keep up with the evolution of their parasites and vice versa
• perpetual coevolution between the two can be compared to an arms race
  “It take all the running you can do, to keep in the same place”- Lewis Carroll

Question 13

mutualistic interactions

Answer 13

corals and zooxanthellae
lichens: fungi and algae
plants and mycorrhizal fungi

Question 14

coral bleaching

Answer 14

caused by:
- change in ocean temp
- runoff and pollution
- overexposure to sunlight
- extreme low tides
- physiological stress causes the loss of pigments and more susceptibility to disease

Question 15

mycorrhizal fungi (MF)

Answer 15

symbiotic relationship b/w fungus and plant associated with plant roots in soil
- arbuscular mycorrhizal fungi (AMF): penetrate cortical cells of plant roots, 80% of plant spp.
- ectomycorrhizal fungi (EMF): no penetration to cortical cells, 2% of plant spp.

some do not have MF

Question 16

mycorrhizae

Answer 16

AMF more mutualistic when grown in nutrient poor soil
- Nancy Johnson

Question 17

mycorrhizae form a mutualism-parasitism continuum

Answer 17

only beneficial for fungi
- plant grown with and without AMF and calculated percentage change of biomass with AMF and with the control
- experiment showed that plant-AMF relationships form a continuum from mutualistic to parasitic interactions

Question 18

mutualism-parasitism continuum

Answer 18

• net effects of cost/benefits
• mutualism to reciprocal parasitism
  (= natural selection should favor a species own fitness rather than simply to “help” organisms)
  ++: beneficial for the plant plant provides carbs to fungus and receives nutrients
  +,-: detrimental for plant: plant provides carbs to fungus but does not receive nutrients

Question 19

non-symbiotic mutualism

Answer 19

not all mutualistic interactions are intricate (“constant body to body”)

Question 20

pollination

Answer 20

transfer of pollen grains for repro by wind, water, animals or within same flower (selfing)

Question 21

animals as pollen dispersal vectors

Answer 21

plant species that rely on animals for pollen dispersal often have very specific pollinators that they have coevolved with

Question 22

attracting pollinators

Answer 22

color and scent
- butterflies: attracted to bright colors (yellow, orange, red): red-blind, attracted to yellow or blue
- nocturnal moths: attracted by heavy-scent released during night

Question 23

rewarding pollinators

Answer 23

pollen, nectar or prospect to mate with a female

Question 24

facultative vs obligate mutualisms

Answer 24

facultative = occurring optionally
no dependence on specific partners (low risk of extinction if partner goes extinct)

obligate = occurring by necessity
dependence on specific partners (high risk of extinction if a partner goes extinct)

Question 25

what do pollinators provide?

Answer 25

ecosystem services

Question 26

bees as commercial pollinators

Answer 26

1/3 of global food production due to pollination
30 billion dollars US/year
facilitated by managed pollinators

Question 27

bees in decline

Answer 27

colony collapse disorder (CCD)
- colonies lacking worker bees and cannot sustain themselves despite abundant honey
- 30% loss each winter which is 3x higher than normal (06)
- parasites, pesticide, poisoning, stress, inadequate forage
- native bumblebees decline

Question 28

measures to counteract pollinator loss

Answer 28

flower strips counteract pollinator loss
increasing landscape heterogeneity