1. The parasite that causes malaria, Plasmodium falciparum, is most closely related to Toxoplasma gondii. Both parasites are eukaryotes, whereas Vibrio cholerae is a bacterium (prokaryote) and H5N1 influenza is a virus (non-living).
2. a. The definitive host of the malaria parasite is the mosquito.
b. The vector of the malaria parasite is also the mosquito.
3. Smallpox elimination was possible because: there are no asymptomatic carriers; the infectious period is short, and the patient is not very contagious before the rash develops; recovery leads to total immunity; there is no animal reservoir; symptoms are easily recognizable; and the vaccine is easy to transport and distribute, inexpensive, and highly effective. (You needed to name any two of these reasons.)
4. a. Viral reassortment occurs when viruses from two separate strains infect a single cell, where they exchange genetic information and create a new, hybrid viral strain.
b. Reassortment of human and bird flu strains is likely to occur in pigs.