ISSN:
1550-7408
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
SYNOPSIS. Phylogenetic relations are ultimately determined by homologous relationships, including both structural and functional data. Following the establishment of those relationships, the direction of evolutionary change must be determined using paleontologic, developmental, and especially morphocline, data. From that perspective the direction of subsequent development becomes clearer and the problems of origins become more explicit.Using the foregoing methodology it has been possible to identify plausibly monophyletic groups of animal protists or protozoa. Allowing for attendant difficulties, there nevertheless emerges certain fairly convincing generalities: (a) the predominantly pseudopodial forms, with a few minor exceptions, have direct origins from apochlorotic algae; (b) the predominantly kinetidal forms (zooflagellates and ciliates), though also derived originally from apochlorotic algae, give evidence of extended evolutionary development with the especially noteworthy emergence of a permanent ingestatory structure; (c) both groups have increased size, a tendency towards multinuclearity and polyploidy, cytoplasmic differentiations of various sorts, and complex life cycles.In terms of further evolution, namely the emergence of multicellular animals, the pseudopodial forms are almost certainly a dead end while the kinetidal forms are arguably the ancestors of at least 2 metazoan phyla.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1550-7408.1976.tb05240.x
