BIO 200 Lecture Notes - Lecture 29: Dicrocoelium Dendriticum, Symbiosis, Monotropa Uniflora

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Parasitism: one symbiont is harmed, one symbiont benefits, parasites are not predators, they do not kill and eat their hosts, ectoparasites: external parasites, example: mistletoe. Attaches to tree, penetrates branches, and absorbs water and nutrients: example: indian pipe. Eats digested food from inside fungus: endoparasites: internal parasites, example: nematodes (roundworms) have a direct life cycle (single host) Eggs are deposited in soil through host feces. Eggs hatch into larvae in the small intestine. Some larvae migrate to the lungs where they are forced into the throat. Larvae molt twice before adulthood: host coughs and re-swallows larvae. Larvae reach adulthood in host intestines and start mating. Eggs are released through host feces: example: plasmodium has multiple hosts. Injects elongated sporozoites (motile, spindle-shaped, asexual cells) into host bloodstream. Sporozoites travel to the liver: rapidly divide asexually (schizogony) inside liver cells, produce merozoites. Merozoites invade other liver cells and host bloodstream.