Life cycle of sporozoans
The complex life cycle of sporozoans typically involves an asexual and a sexual phase. Sporozoans are haploid except for the zygote. The zygote undergoes meiosis that results in an infective spore like stage the sporozoite which by multiple fission produces more sporozoites. These invade the host and become feeding trophozoite.
Figure: Life cycle of coccidian sporozoans. All stages are haploid except zygote
In some sporozoans the trophozoites, by multiple fision known as schizogony produce merozoites. Each merozoite undergoes multiple fission to produce more merozoites that eventually undergo gamogony or multiple fissions to form gametes that fuse to form zygote.