<P> Within the red blood cells, the merozoites grow first to a ring - shaped form and then to a larger form called a trophozoite . Trophozoites then mature to schizonts which divide several times to produce new merozoites . The infected red blood cell eventually bursts, allowing the new merozoites to travel within the bloodstream to infect new red blood cells . Most merozoites continue this replicative cycle, however some merozoites upon infecting red blood cells differentiate into male or female sexual forms called gametocytes . These gametocytes circulate in the blood until they are taken up when a mosquito feeds on the infected vertebrate host, taking up blood which includes the gametocytes . </P> <P> In the mosquito, the gametocytes move along with the blood meal to the mosquito's midgut . Here the gametocytes develop into male and female gametes which fertilize each other, forming a zygote . Zygotes then develop into a motile form called an ookinete, which penetrates the wall of the midgut . Upon traversing the midgut wall, the ookinete embeds into the gut's exterior membrane and develops into an oocyst . Oocysts divide many times to produce large numbers of small elongated sporozoites . These sporozoites migrate to the salivary glands of the mosquito where they can be injected into the blood of the next host the mosquito bites, repeating the cycle . </P> <P> Plasmodium belongs to the phylum Apicomplexa, a taxonomic group of single - celled parasites with characteristic secretory organelles at one end of the cell . Within Apicomplexa, Plasmodium is within the order Haemosporida, a group that includes all apicomplexans that live within blood cells . Based on the presence of the pigment hemozoin and the method of asexual reproduction, the order is further split into four families, of which Plasmodium is in the family Plasmodiidae . </P> <P> The genus Plasmodium consists of over 200 species, generally described on the basis of their appearance in blood smears of infected vertebrates . These speces have been categorized on the basis of their morphology and host range into 14 subgenera: </P>

Part b - the life cycle of plasmodium