BIEB 166 Section 2 Review

BIEB 166 Section 2 Review - Fatal attraction in rats...

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“Fatal attraction in rats infected with Toxoplasma gondii” by M. Berdoy, J.P. Webster, and D.W. Macdonald Manipulation hypothesis: a parasite alters the behavior of its host for its own benefit (i.e. to enhance transmission) Author’s Hypothesis: The parasite Toxoplasma gondii manipulates the behavior of its intermediate rat host in order to increase its chance of being predated by cats, its feline definitive host, thereby ensuring the completion of its life cycle. Background Toxoplasma gondii is immature in “intermediate hosts,” and must enter a “definitive host” in order to reach maturity and complete its life cycle. -Intermediate hosts include rats and humans -Definitive host is the cat T. gondii -intracellular protozoan -can infect any mammal -members of the cat family are the only definitive hosts and only known mammals to shed the T. gondii oocysts with their feces Proximal Question: What might be reasons that the cat family is the only definitive host for this organism? Possible hypothesis: -Cats lack an enzyme that degrades oocyst in digestive tract that other mammals express Ultimate Question: Why has T. gondii evolved such that cats are its only definitive host? Possible hypotheses: -T. gondii may have evolved in a region with a mammal population consisting primarily of cat species -Other mammals may have initially been definitive hosts, but evolved in such a way that they were no longer viable as definitive hosts
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BIEB 166 Section 2 Review - Fatal attraction in rats...

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