Lecture 23: Parasitism and Mutualism

Question 1

Obligate vs facultative mutualism

Answer 1

Obligate: one organism cannot survive without the other (ex: fig-wasp mutualism) - high risk of extinction

Facultative: can survive without their mutualist - low risk of extinction

Question 2

What are the 3 types of mutualism?

Answer 2

1. service-service relationship: clownfish and anemones
2. resource-resource relationship: fungi and plant roots
3. service-resource relationship: pollination, cleaning symbiosis, zoochory

Question 3

Service-resource: Explain zooxanthellae

Answer 3

• single-celled dinoflagellate that photosynthesize inside of coral tissue
• provides coral with glucose, glycerol, and amino acids
• coral provides zooxanthellae with protection and co2

Question 4

What causes coral bleaching?

Answer 4

Change in ocean temps, runoff, pollution, overexposure to sunlight, and low tides

Question 5

Service-resource: lichens and algae

Answer 5

Lichens contain fungal filaments that help feed and protect the algae. Algae provide the lichens with nutrients via photosynthesis

Question 6

How do you categorize mutualistic relationships by the type of benefit they receive?

Answer 6

Trophic mutualism: receive energy from their partner

Habitat mutualism: receive shelter or habitat from their partner

Question 7

What is the virulence theory?

Answer 7

Virulence factors are maintained because they aid in parasitic exploitation, increasing growth or transmission between hosts - antagonism leads to mutualism

Question 8

How does a mutualistic relationship become parasitic?

Answer 8

Once net costs exceed net benefits - relationship becomes disadvantageous to both partners

Ex: mycorrhizae

Question 9

What are the types of parasitic relationships?

Answer 9

• endoparasites: living inside the host
• ectoparasites: living outside the host
• mesoparasites: enters host through an opening

Question 10

What kind of forms do parasites take?

Answer 10

• brood parasites: relying on others to raise their young
• kleptoparasites: stealing food gathered by the host
• sexual parasites: difference in body size of male and female anglerfish

Question 11

What are some ways parasites are transmitted?

Answer 11

• vector-transmitted: requires a third party
• directly-transmitted: does not require a vector
• parasitoids: insects that kill their host
• trophically-transmitted: requires the host to consume them

Question 12

What is the red-queen hypothesis?

Answer 12

An “arms race” of continuous evolution in order to avoid extinction - evolution in sex, mating systems, pathogen virulence, and maintenance of genetic diversity