Biology, Eighth Edition (Raven)

Chapter 20: Genes Within Populations

Malaria: Life Cycle of Plasmodium

What is an advantage of having two different host species for Plasmodium? The organism causing malaria, Plasmodium, has a two host life cycle. In order to complete the life cycle, Plasmodium must move from mosquito to human and then back to mosquito again. Having two hosts may seem inefficient but it is very common in eukaryotic parasites. If Plasmodium only had a single host, either humans or mosquitoes, it would be difficult for the parasite to move to a new host individual. Eukaryotic parasites generally cannot move from host to host by casual contact. Mosquitoes feed on human blood and the transfer of blood and anticoagulant between humans and mosquitoes allows for the predictable transfer of the parasite.

View the animation below, then complete the quiz to test your knowledge of the concept.


1.	Malaria is transmitted to humans by the Anopheles mosquito, which injects the _______ stage of the organism Plasmodium.

		A)	oocyst
		B)	gametocyte
		C)	schizont
		D)	merozoite
		E)	sporozoite

2.	Arrange the following in the proper order in which they occur during the human-phase of the Plasmodium life cycle. 1. Formation of schizont 2. Invasion of the liver 3. Invasion of red blood cells

		A)	1, 2, 3
		B)	2, 1, 3
		C)	2, 3, 1
		D)	3, 2, 1
		E)	3, 1, 2

3.	Arrange the following in the proper order in which they occur during the mosquito-phase of the Plasmodium life cycle. 1. Formation of zygote 2. Formation of oocyst 3. Formation of sporozoites

		A)	1, 2, 3
		B)	2, 1, 3
		C)	2, 3, 1
		D)	3, 2, 1
		E)	3, 1, 2

4.	Plasmodium gametocytes are capable of producing gametes in mosquitoes, but not in human hosts.

		A)	True
		B)	False

5.	The liver cells of people infected with malaria contain the ring trophozoite form of Plasmodium.

		A)	True
		B)	False