Mutualism

Question 1

What is mutualism and some examples?

Answer 1

Mutualism describes the ecological interaction between two or more species where each species has a net benefit.

→ have costs and benefits

• Pollination - pollinators disperse pollen and gain reward like nectar
• Acacia ants - ants protect plants and plants give them safe place to live

Question 2

What are the types of mutualism? (facultative, obligate)

Answer 2

Facultative (non obligate)

A type of mutualism in which the interacting species derive benefit from each other but not being fully dependent that each cannot survive without the symbiotic partner.

Obligate - otherwise either population will go extinct

Question 3

How are mutualist interactions prone to exploitation? (selfish, policing mechanism)

Answer 3

→ Selfish nature of natural selection will result in exploitation of +/+ interactions in absence of ‘Policing mechanisms’

e.g Nitrogen Fixing Bacteria in legumes of plants

• in nitrogen rich soil - not mutually beneficial interaction
  
  • only beneficial to bacteria
  • therefore plant cuts off N-fixing bacteria

Question 4

What is the stress gradient hypothesis?

Answer 4

= positive interactions are more prevalent in harsher environments

strength of competition declines with stress
strength of facilitation increases with stress