amensalism
A symbiotic relationship in which one organism is harmed or
inhibited and the other is unaffected. Examples of amensalism
include the shading out of one plant by a taller and wider one and
the inhibition of one plant by the secretions of another (known as
allelopathy).
secretion
1. The process of secreting a substance from a cell or gland.
2. A substance, such as saliva, mucus, tears, bile, or a
hormone, that is secreted.
commensalism adj. Of, relating to, or characterized by a
symbiotic relationship in which one species is benefited while the
other is unaffected.
mutualism
A symbiotic relationship in which each of the organisms benefits.
◇ In obligate mutualism the interacting species are
interdependent and cannot survive without each other. The fungi
and algae that combine to form lichen are obligate mutualists. ◇
In the more common facultative mutualism the interacting
species derive benefit without being fully dependent. Many plants
produce fruits that are eaten by birds, and the birds later excrete
the seeds of these fruits far from the parent plant. While both
species benefit, the birds have other food available to them, and
the plants can disperse their seeds when the uneaten fruit drops.
parasitism
A symbiotic relationship in which one organism (the parasite)
benefits and the other (the host) is generally harmed. Parasites
derive nutrition from their host and may also gain other benefits
such as shelter and a habitat in which to grow and reproduce.