Heterotrophic Nutrition

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An ecological relationship between organisms of two different species that live together in direct contact. nationalzoo.si.edu/Animals/Primates/glossary.cfm

Symbiosis

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A mutually beneficial relationship between two organisms. www.powen.freeserve.co.uk/Reference/Glossary/gloss-s.htm

A close, prolonged association between two or more different organisms of different species that may, but does not necessarily, benefit each member. www.freakinfucus.co.uk/primers/prm_gloss.htm

Symbiosis

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Most of the interactions between species involve food:

competing for the same food supply

eating (predation)

avoiding being eaten (avoiding predation)

Symbiosis

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In symbiosis, at least one member of the pair benefits from the relationship. The other member may be

injured = parasitism

relatively unaffected ( = commensalism)

may also benefit ( = mutualism).

Symbiosis

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Mutualism

Symbiotic relationships in which each species benefits are mutualistic. There are hundreds of examples of mutualism between a heterotroph and an alga.

Symbiosis

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Paramecium bursaria is a ciliate that engulfs unicellular green algae into vacuoles within its cell.

The paramecium certainly benefits from the food synthesized by the alga. It can be cultured apart from the alga but then must be given extra food.

The alga presumably benefits from the carbon dioxide produced by its host as well as the host's ability to transport it to a spot where there is ample light.

Symbiosis

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Many other aquatic heterotrophs

sponges

sea anemones

planarians

clams

also harbor algae within their cells.

Symbiosis

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liberating toxins, for example,

Tetanus bacilli secrete tetanus toxin which interferes with synaptic transmission.

Diphtheria bacilli secrete a toxin that inhibits protein synthesis by ribosomes.

The relationship between parasite and host varies along a spectrum that extends from

Symbiosis

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Mutualistic relations between plants and fungi are very common. The fungus invades and lives in or among the cortex cells of the secondary roots. The association is called a mycorrhiza.

Symbiosis