Final answer:
Plasmodium, a protozoan parasite transmitted by Anopheles mosquitoes, causes malaria in humans and is prevalent in tropical and subtropical regions due to the ecological needs of the mosquito.
Step-by-step explanation:
Plasmodium and Malaria
Plasmodium, a protozoan parasite, is responsible for causing malaria in humans. These parasites are spread by a mosquito vector, specifically, Anopheles mosquitoes. Upon biting a human, the mosquito transmits the Plasmodium sporozoites into the bloodstream. These sporozoites travel to the liver, mature, and then infect red blood cells. The most dangerous of the species, Plasmodium falciparum, is notorious for severe symptoms such as anemia, fever, and in some cases, death. Efforts to prevent malaria include mosquito control measures and the use of mosquito netting to prevent bites. The geographical distribution of malaria is typically constrained to tropical and subtropical regions due to the climate preferences of the mosquito vectors.