Editing Apicomplexa (section)

==Life cycle==
{{Further|Apicomplexa lifecycle stages}}
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| caption1 =Generic lifecycle of an Apicomplexan: 1-[[zygote]] ([[Microbial cyst|cyst]]), 2-[[sporozoite]]s, 3-[[merozoite]]s, 4-[[gametocyte]]s
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Most members have a complex lifecycle, involving both asexual and sexual reproduction.  Typically, a host is infected via an active invasion by the parasites (similar to [[entosis]]), which divide to produce [[sporozoite]]s that enter its cells.  Eventually, the cells burst, releasing [[merozoites]], which infect new cells.  This may occur several times, until gamonts are produced, forming gametes that fuse to create new cysts.  Many variations occur on this basic pattern, however, and many Apicomplexa have more than one host.<ref>{{Cite journal |last1=Templeton |first1=Thomas J. |last2=Iyer |first2=Lakshminarayan M. |last3=Anantharaman |first3=Vivek |last4=Enomoto |first4=Shinichiro |last5=Abrahante |first5=Juan E. |last6=Subramanian |first6=G.M. |last7=Hoffman |first7=Stephen L. |last8=Abrahamsen |first8=Mitchell S. |last9=Aravind |first9=L. |date=September 2004 |title=Comparative Analysis of Apicomplexa and Genomic Diversity in Eukaryotes |journal=Genome Research |volume=14 |issue=9 |pages=1686–1695 |doi=10.1101/gr.2615304 |issn=1088-9051 |pmid=15342554|pmc=515313 }}</ref>

The apical complex includes [[Vesicle (biology)|vesicle]]s called [[rhoptries]] and [[microneme]]s, which open at the anterior of the cell.  These secrete enzymes that allow the parasite to enter other cells.  The tip is surrounded by a band of [[microtubule]]s, called the polar ring, and among the Conoidasida is also a funnel of tubulin proteins called the conoid.<ref name=coccidiaworld>{{cite web|url=http://biology.unm.edu/biology/coccidia/home.html|title=The Coccidia of the World|last1=Duszynski|first1=Donald W.|first2=Steve J.|last2=Upton|first3=Lee|last3=Couch|publisher=Department of Biology, University of New Mexico, and Division of Biology, Kansas State University|date=2004-02-21|format=Online database|access-date=2006-10-04|archive-url=https://web.archive.org/web/20101230215149/http://biology.unm.edu/biology/coccidia/home.html|archive-date=2010-12-30|url-status=dead}}</ref>   Over the rest of the cell, except for a diminished mouth called the micropore, the membrane is supported by vesicles called alveoli, forming a semirigid pellicle.<ref name="Angel. 2018">{{Cite book|last=Angel.|first=Sherman|url=http://worldcat.org/oclc/1132400230|title=Medical Parasitology|date=2018|publisher=EDTECH|isbn=978-1-83947-353-1|oclc=1132400230}}</ref>

The presence of alveoli and other traits place the Apicomplexa among a group called the [[alveolate]]s. Several related flagellates, such as ''[[Perkinsus marinus|Perkinsus]]'' and ''[[Colpodella]]'', have structures similar to the polar ring and were formerly included here, but most appear to be closer relatives of the [[dinoflagellate]]s.  They are probably similar to the common ancestor of the two groups.<ref name="Angel. 2018"/>

Another similarity is that many apicomplexan cells contain a single [[plastid]], called the [[apicoplast]], surrounded by either three or four membranes.  Its functions are thought to include tasks such as lipid and heme biosynthesis, and it appears to be necessary for survival.  In general, plastids are considered to have a common origin with the chloroplasts of dinoflagellates, and evidence points to an origin from [[red algae]] rather than [[green alga|green]].<ref>{{cite journal | journal = American Journal of Botany | year = 2004 | volume = 91 | pages = 1481–1493 | title = Diversity and evolutionary history of plastids and their hosts | author = Patrick J. Keeling | doi = 10.3732/ajb.91.10.1481 | issue=10 | pmid=21652304| doi-access = free }}</ref><ref>{{cite journal | doi = 10.1093/nar/gkn483 |date=July 2008 |author1=Ram, Ev |author2=Naik, R |author3=Ganguli, M |author4=Habib, S | title = DNA organization by the apicoplast-targeted bacterial histone-like protein of Plasmodium falciparum | volume =  36| issue =  15| pages =  5061–73| pmid = 18663012 | journal = Nucleic Acids Research | pmc = 2528193 }}</ref>