Many different relationships exist between organisms in an ecosystem. These relationships include competition for food, shelter,
and other resources as well as predation in which one organism kills and consumes another for food. There are also symbiotic
relationships. Symbiosis is a close relationship between two species in which at least one species benefits. For the other species, the
relationship may be positive, negative, or neutral. There are three basic types of symbiosis: mutualism, commensalism, and parasitism.'
Evaluate each of the relationships depicted in the choices. Select ALL the relationships illustrating commensalism.
es 0)
A)
Hermit crabs use the shells of dead snails for homes.
B)
Egrets perch on the back of cows and eat the insects that have been
disturbed as the cattle forage for food.
C)
Fleas get food and a warm home by living on hosts such as dogs or cats
and biting them to get nutrients from their blood.
D
The Egyptian Plover or "Crocodile Bird" will fly into the crocodile's open
mouth and feed on the decomposing meat stuck between their teeth
E)
The pilot fish helps to rid the shark of parasites and clean away fragments
of food caught between their teeth, it benefits from protection against
other predators.
Answer: A . Hermit crabs use the shells of dead snails for homes & B. Egrets perch on the back of cows and eat the insects that have been distributed as the cattle forage for food.
