sp02u3p2 - Unit Three Single-celled Organisms Unit III...

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Unit Three Single-celled Organisms ©Project Oceanography Spring 2002 76 Unit III Single-celled Organisms On the cutting edge… Dr. Wood at the University of Oregon is on the edge of scientific discovery as she explores some of the microscopic inhabitants of the marine environment. She is studying the relationship between a cyanobacteria and a dinoflagellate. She is interested in learning more about how these organisms create a symbiotic relationship that helps them succeed in nutrient-poor tropical waters. Introduction to Single-celled Organisms Lesson Objectives: Students will be able to do the following: Compare and contrast three types of symbiotic relationships Describe the relationship between zooxanthellae and coral Explain the effects of nitrogen-fixing bacteria on their symbiotic partners Key concepts: symbiosis, commensalism, parasitism, mutualism, dinoflagellate, nitrogen-fixing cyanobacteria Symbiotic Relationships The word symbiosis in its simpliest terms means “living together”. This word describes a partnership between two different kinds of organisms such as a sea anemone and a hermit crab or a squid and a bacterium . These relationships are long-term associations that are usually advantageous to at least one member of the partnership. These symbiotic relationships often occur because of the nutritional needs of the members. There are many examples of symbiosis to be found in nature. For example, some hermit crabs have shells covered with sea anemones. The crab is camouflaged from predators and protected with the sea anemones’ tentacles while the anemones are carried to various locations where food gathering is easier. The bobtail squid harbors light emitting bacteria. These bacteria help create light patterns that camouflage the squid during hours of feeding. Symbiotic relationships can be divided into three broad categories: commensalism , parasitism , and mutualism . These categories describe how each partner benefits from the relationship. In commensalism, one member benefits while the other is neither helped nor harmed. A good example
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Unit Three Single-celled Organisms ©Project Oceanography Spring 2002 77 of this type of relationship is the remora that can attach itself to a shark. The remora gets a free ride and eats the scraps left by the shark. It does not harm or help the shark. In parasitism, one member is helped while the other member is harmed. An example of a parasitic relationship is a tapeworm in a human. The parasite , the tapeworm, lives inside the human or host . The parasite is helped, because it gets nutrition from the food in the human’s intestine. The human can slowly starve, because the tapeworm is using the nutrition from the food the human eats. In mutualism, both organisms benefit as in the case of the fish and the cleaner shrimp. The fish enters a
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sp02u3p2 - Unit Three Single-celled Organisms Unit III...

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