The life cycle Some parasites are complex and involve multip

The life cycle Some parasites are complex and involve multiple hosts Discuss this statement using named examples that can be found in the kingdom Protista.

Solution

Parasites with more complex life cycles involving multiple hosts are described as having indirect or heteroxenous life cycles. The primary host of a heteroxenous species is the one in which adult parasites live and reproduce. The secondary or intermediate host is used by immature life stages of the parasite. The intermediate host may also aid in transmitting parasites to their final host. Fleas, for example, are sometimes intermediate hosts for mammalian parasites such as tapeworms.

Parasitic flukes have a complex life cycle often involving several hosts

Life cycle of a blood fluke miracidia swims and enters snail and develops into sporocyst, sporocysts divde to form redia, redia give rise to cercaria and enter the body as metacercaria

Life cycle of the roundworm wuchereria bancrofti: roundworm produces microfilaria and causes elephantiasis of the legs and scrotum.

Life cycle of the beef tapeworm: eggs are passed in feces onto grade, feces disintegrate and leave eggs on grass, cow eats the grass and becomes infected, eggs hatch and larvae burrow through intestinal wall and enter the bloodstream, the infected embryo in meat are ingested in rare or undercooked meat.