What affects almost 5 billion people worldwide, kills more than 20 million people every year (many of them children), and costs governments billions of dollars annually in lost productivity, crops, and livestock?

Parasitism

Review Symbiosis: a close association between members of two species. No benefit or damage is indicated by this term. Symbiont: an organism involved in a symbiotic relationship

Parasitism Parasitism: A symbiotic relationship in which one species, the parasite, is dependent on the other species, the host, for its survival and causes harm to the host.

Parasite Parasite: An organism that lives in close association with a host for part or all of its life cycle and is dependent upon the host for nutrients, developmental cues, shelter, or other elements.

Parasite General Characteristics of Parasites:

Host Host: an organism that harbors a parasite and is harmed by the parasite’s presence. Harm may be in the form of lost nutrients, physical damage to tissues, or a severe immune response to the parasite.

Host General Characteristics of hosts:

Examples of Parasitism Mosquitoes – Female mosquitoes drink blood Provides protein for egg-laying – Harm to host Blood loss, inflammation Vector-Borne diseases

Examples of Parasitism Malaria – Transmitted by mosquitoes – Microscopic – Lives inside hosts for entire life Gains protection, nutrients, etc – Harm to host Serious disease, anemia, death

Question 1 Is the following an example of parasitism? Certain birds ride on the backs of rhinos and eat the insects they find there, reducing irritating biting for the rhinoceri.

Question 2 Is the following an example of parasitism? Toxoplasma gondii lives inside of rats and alters their behavior so that they are attracted to the smell of cat urine, rather than avoiding it.

Image references Hookworm: Mosquito: Source unknown Plasmodium: Rhino: Toxoplasma: Remy: Property of Disney/Pixar, Inc.