Editing Alveolate (section)

==Evolution==
A Bayesian estimate places the evolution of the alveolate group at ~{{ma|850}}.<ref name=Berney2006>{{cite journal | last1 = Berney | first1 = C | last2 = Pawlowski | first2 = J | year = 2006 | title = A molecular time-scale for eukaryote evolution recalibrated with the continuous microfossil record | journal = Proc Biol Sci | volume = 273 | issue = 1596| pages = 1867–72 | doi=10.1098/rspb.2006.3537| pmc = 1634798 | pmid=16822745}}</ref> The Alveolata consist of [[Myzozoa]], [[Ciliates]], and Colponemids. In other words, the term Myzozoa, meaning "to siphon the contents from prey", may be applied informally to the common ancestor of the subset of alveolates that are neither ciliates nor colponemids. Predation upon algae is an important driver in alveolate evolution, as it can provide sources for endosymbiosis of novel plastids.  The term Myzozoa is therefore a handy concept for tracking the history of the alveolate phylum.

The ancestors of the alveolate group may have been photosynthetic.<ref name=Reyes-Prieto>{{cite journal|last1=Reyes-Prieto|first1=A|last2=Moustafa|first2=A|last3=Bhattacharya|first3=D|title=Multiple genes of apparent algal origin suggest ciliates may once have been photosynthetic.|journal=Curr. Biol.|date=2008|volume=18|issue=13|pages=956–62|doi=10.1016/j.cub.2008.05.042|pmid=18595706|pmc=2577054|bibcode=2008CBio...18..956R}}</ref> The ancestral alveolate probably possessed a [[plastid]]. Chromerids, apicomplexans, and peridinin dinoflagellates have retained this [[organelle]].<ref>{{cite journal |vauthors=Moore RB, Oborník M, Janouskovec J, Chrudimský T, Vancová M, Green DH, Wright SW, Davies NW, Bolch CJ, Heimann K, Slapeta J, Hoegh-Guldberg O, Logsdon JM, Carter DA |title=A photosynthetic alveolate closely related to apicomplexan parasites |journal=Nature |volume=451 |issue=7181 |pages=959–963 |year=2008 |pmid=18288187 |doi=10.1038/nature06635 |bibcode=2008Natur.451..959M |s2cid=28005870 }}</ref> Going one step even further back, the chromerids, the peridinin dinoflagellates and the [[Heterokont|heterokont algae]] have been argued to possess a monophyletic plastid lineage in common, i.e. acquired their plastids from a [[red alga]],<ref name="Janouskovec2010"/> and so it seems likely that the common ancestor of alveolates and heterokonts was also photosynthetic.

In one school of thought the common ancestor of the [[dinoflagellates]], [[apicomplexans]], ''[[Colpodella]]'', [[Chromerida]], and ''[[Voromonas]]'' was a myzocytotic predator with two heterodynamic [[flagella]], [[micropore]]s, [[trichocyst]]s, [[rhoptries]], [[microneme]]s, a polar ring and a coiled open sided [[conoid]].<ref name=Kuvardina2002>{{cite journal | last1 = Kuvardina | first1 = ON | last2 = Leander | first2 = BS | last3 = Aleshin | first3 = VV | last4 = Myl'nikov | first4 = AP | last5 = Keeling | first5 = PJ | last6 = Simdyanov | first6 = TG | year = 2002 | title = The phylogeny of colpodellids (Alveolata) using small subunit rRNA gene sequences suggests they are the free living sister group to apicomplexans | journal = J Eukaryot Microbiol | volume = 49 | issue = 6| pages = 498–504 | doi=10.1111/j.1550-7408.2002.tb00235.x | pmid=12503687| title-link = colpodellid | s2cid = 4283969 }}</ref> While the common ancestor of alveolates may also have possessed some of these characteristics, it has been argued that Myzocytosis was not one of these characteristics, as ciliates ingest prey by a different mechanism.<ref name=Tikhonenkov14/>

An ongoing debate concerns the number of membranes surrounding the plastid across apicomplexans and certain dinoflagellates, and the origin of these membranes. This ultrastructural character can be used to group organisms and if the character is in common, it can imply that phyla had a common photosynthetic ancestor. On the basis that apicomplexans possess a plastid surrounded by four membranes, and that peridinin dinoflagellates possess a plastid surrounded by three membranes, Petersen et al.<ref>{{cite journal |vauthors=Petersen J, Ludewig AK, Michael V, Bunk B, Jarek M, Baurain D, Brinkmann H |title=''Chromera velia'', endosymbioses and the rhodoplex hypothesis—plastid evolution in cryptophytes, alveolates, stramenopiles, and haptophytes (CASH lineages) |journal=Genome Biol Evol |volume=6 |issue=3 |pages=666–684 |year=2014 |pmid=24572015 |pmc=3971594 |doi=10.1093/gbe/evu043 }}</ref> have been unable to rule out that the shared stramenopile-alveolate plastid could have been recycled multiple times in the alveolate phylum, the source being stramenopile-alveolate donors, through the mechanism of ingestion and [[endosymbiosis]].

Ciliates are a model alveolate, having been genetically studied in great depth over the longest period of any alveolate lineage. They are unusual among eukaryotes in that reproduction involves a [[micronucleus]] and a [[macronucleus]]. Their reproduction is easily studied in the lab, and made them a model eukaryote historically. Being entirely predatory and lacking any remnant plastid, their development as a phylum illustrates how predation and autotrophy<ref name="Reyes-Prieto"/> are in dynamic balance and that the balance can swing one way or other at the point of origin of a new phylum from mixotrophic ancestors, causing one ability to be lost.

<gallery class="center" mode="nolines" widths=200 heights=200>
File:Paramecium caudatum Ehrenberg, 1833.jpg|''[[Paramecium|Paramecium caudatum]]'' ([[Ciliophora]])
File:Mikrofoto.de-Glockentierchen-1.jpg|''[[Vorticella]]'' ([[Ciliophora]]) (left)
File:Plasmodium.jpg|''[[Plasmodium falciparum]]'' ([[Apicomplexa]]) in blood
File:Emaxima oocysts usda.jpg|''[[Eimeria|Eimeria maxima]]'' ([[Apicomplexa]])
File:Dinophysis acuminata.jpg|''[[Dinophysis|Dinophysis acuminata]]'' ([[Dinoflagellata]])
</gallery>