Powerpoint: Feb 17 Symbiosis
Learning Objectives
- Define symbiosis
- Define and give examples of parasitism, commensalism and mutualism
Most organisms in an ecosystem share some sort of relationship with each other. In these relationships, at least one party will benefit.
Symbiosis close relationship between two species in which at least one species benefits from the other.
| Relationship | Nature of relationship | Examples |
| Parasitism | + / – (One party suffers while the other benefits) |
Parasites (e.g. the tongue eating louse) |
| Commensalism | + / o (one party benefits, the other is unaffected) | Example humans and pigeons
Licorice fern and tree |
| Mutualism | +/+ (where both parties benefit) | Red alder and nitrogen fixing bacteria. (exchange of sugar and nitrogen).
Corals and photosynthetic bacteria. |
Challenge question: from an evolutionary standpoint, why don’t we see relationships where neither party benefits?