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How closely related (from the evolutional point of view) are parasites Giardia intestinalis and Trichomonas vaginalis? Giardia genome is about 12 Mb and its major cellular proceses are rather simple. The genome of Trichomonas is approximately 160 Mb. What about its cellular processes, is it also a 'minimalist'?

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Basically, Giarda is a an Excavates while Trichomonas is a Cercozoa meaning a Rhizaria (Chromealveolates in the broad sense as noticed by @har-wradim in the comments (now deleted) because Cercozoa are neither Chromista nor alveolata). Because the very basis of the tree of eukaryotes is still unresolved (eukaryotes), the most recent common ancestor of these two species is just an old eukaryote! In other words, these two species are not more closely related than are related a cat and a chestnut tree!

The links yield to Tolweb.org which shows you the phylogenetic tree and allows you to explore the relationships between organisms. Have a look to eukaryote tree especially to see the positions of the Rhizaria and Cercozoa.

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  • $\begingroup$ One more point: While Giardia and Trichomonas both lack mitochondria, the former has mitosomes and the latter has hydrogenosomes. Mitosome has the most reduced functionality $\endgroup$ – WYSIWYG Sep 17 '14 at 4:17
  • $\begingroup$ Be careful though that Tolweb is not always very up-to-date. $\endgroup$ – bli Sep 17 '14 at 13:40

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