Do you know that a tiny organism living inside you helps keep you alive?  That organism is E. coli, a bacterium that lives in your intestines.  E. coli provides you with vitamins; you provide E. coli with food.  This relationship is calledmutualism, because both you and E. coli benefit.

Directions:  Read the following descriptions of each relationship.  Then complete columns two and three of the table.  In column two, state whether eachorganism benefits, suffers, or is not affected.  In column three, classify the relationships as mutualism, commensalism, or parasitism.

A.    Orchid vines grow up the trunks of trees.  The areas at the tops of trees have more light than the areas underneath trees.  The trees are not affected by the orchids.

B.    A type of bacteria that lives on the roots of bean and pea plants converts nitrogen gas in the air into nitrogen compounds that the plants need for growth.

C.    A lamprey eel fastens itself to a host fish, such as lake perch, and feeds on it.  When the fish dies, the lamprey finds another host.

D.    A remora attaches itself to sharks by a rough, flattened fin on the top of its head.  It feeds on shreds of the sharks' prey.

E.    Fungal hyphae live on the roots of plants.  The fungal hyphae improve the nutrient uptake of the roots, protect the plants from pathogens, and produce plant growth hormones.  The fungi get carbohydrates from the plant.

F.    Hookworms attached to the intestinal walls of humans get nutrients from the host's blood and tissue juices.  Infected humans experience digestive disorders and anemia.

G.    Polyergus rufescens ants steal the eggs of Formica fusca ants.  When the eggs hatch, the Formica ants become slave workers for the Polyergus ants.

H.    Species of small fishes and shrimp remove parasites from larger fishes.  The small fishes get nutrients from the parasites and the large fishes are cleaned of parasites.

I.    Yucca moths lay their eggs in the seed pods of yucca plants.  Larvae that hatch from the yucca moth's eggs feed on some, but not all, the seeds.  The plant is pollinated by the moth.

J.    Brittle stars make their homes in tropical sponges.

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