Beneficial interactions - mutualism

Question 1

Define mutualism

Answer 1

Mutually beneficial interaction between 2 species

Question 2

Define commensalism

Answer 2

1 species benefit, other species do not, but are not harmed

Question 3

Describe the results of the ‘cleaner’ fish experiment

Answer 3

No cleaner fish = no. of parasites increased

–> thus mutualism

Question 4

Describe the clown fish & anemone commensalism

Answer 4

Anemones tentacles produce poison
–> kill/paralyse small fish

Clownfish = poison resistant
–> protected by anemone BUT anemone gain nothing

Question 5

Define symbiosis

What are the 3 types?

Answer 5

Relationship in which 2 species live in close physiological contact w/ each other
e.g. corals & algae

Parasitism
Commensalism
Mutualism

Question 6

What are the benefits of mutualistic associations?

Answer 6

> nutrients
protection/defence
reproduction
dispersal

Question 7

Give examples of nutrition mutualisms

Answer 7

Rhizobium - N fixing
Endomycorrhizae = grow inside roots & facilitate P uptake
Ectomycorrhizae = grow on roots & supply N by decomposition

Question 8

Which example is commonly used to describe nutritional mutualism?

Answer 8

Fungus farming ants

Fungus digests cellulose in leaves collected by ants
–> Ants eat fungus

Question 9

Give examples of protection mutualisms

Answer 9

Ants & Acacias

• tree covered in spikes which ants raise young in
• tree produces ‘fruits; to feed ants
• ants eat everything around tree = reduce competition for light
• ants also reduce herbivory

Question 10

Give an example of reproduction mutualism

What can this lead to?

Answer 10

Plants get ovules fertilised
- animals get pollen/nectar as food source

Specialisation
= more efficient pollinating

Question 11

Give an example of dispersal mutualisms

Answer 11

Omphalocarpum procera v large seeds/fruit
- eaten by elephants
= food for them & dispersal for plant

Question 12

What may the nature of an association depend on?

Answer 12

Environment

Question 13

Give an example of when an association depends on the enviro.

Answer 13

Oropendolas tolerate cowbirds when parasitism improves fitness
- cowbird chicks remove botfly larvae from oropendola eggs

Oropendolas reject cowbird eggs when parasitism reduces fitness
- if nest is near wasps that protect from botflies
(Cowbirds then mimic oropendola eggs)

Question 14

Give an example of a facilitative mutualism

Answer 14

Plants & mycorrhizae

High-nutrient enviro –> plants reduce carbohydrates to mycorrhizal fungi

Question 15

Why can’t deforested areas recover once they get too big?

Answer 15

As area gets larger, fewer animals go across area

= less dispersal of seed

Question 16

How do mutualisms evolve?

Answer 16

Probably from initially antagonistic relationships

Question 17

Give an example of a mutualism evolving

Answer 17

Pollen feeding occasionally led to increased rate of pollen transfer

• plants w/ mechanisms to entice pollen feeders had increased success
• pollinators specialised to transfer pollen had increased success as could obtain resources not available to other pollinators

Question 18

Describe the experimental evolution experiment

Answer 18

Strain of Amoeba proteus inoculated w/ bacteria
–> initially bacteria caused hosts to be smaller, grow slowly & often kill hosts
–> 5 yrs later bacteria evolved to be harmless to amoebae
& amoeba dependent on bacteria for metabolic functions

Question 19

Define an obligate symbiotic relationship

Answer 19

Both species live in permanent close relationship

Question 20

Give 2 examples of obligate symbiotic relationships

Answer 20

Lychen = algae + cyanobacteria

Human mitochondria