Economics 1021A/B Lecture Notes - Lecture 14: Algae, Field Experiment, Coevolution

• School: Western University
• Department: Economics
• Course: Economics 1021A/B
• Professor: Tim Hain

Document Summary

Nonresident fungi, pathogens, and parasites can sometimes invade the colonies. The bacteria also benefit: they get a place to live (in specialized structures called crypts on the a(cid:374)t"s e(cid:454)oskeleto(cid:374)(cid:895), a(cid:374)d a sour(cid:272)e of food (cid:894)gla(cid:374)dular se(cid:272)retio(cid:374)s(cid:895) fro(cid:373) the a(cid:374)ts. Positive interactions occur when neither species is harmed and the benefits of the interaction are greater than the costs for at least one species. Mutualism: mutually beneficial interaction between individuals of two species (+/+) Commensalism: individuals of one species benefit, while individuals of the other species do not benefit and are not harmed (+/0) Symbiosis: a relationship in which the two species live in close physiological contact with each other, such as corals and algae: symbioses can include parasitism (+/ ), commensalism (+/0), and mutualism (+/+) The benefits of positive interactions can take many forms: sometimes there is a cost to one or both partners, but the net effect is positive, for each species, the benefits are greater than the costs.