Holozoa is a group of organisms that includes animals and their closest single-celled (protist) relatives, but excludes fungi and all other organisms. It is a monophyletic group or clade, a lineage consisting of all descendants of a common ancestor. Among these descendants, the protists are of high interest because of their close relationship to animals: in the search for the genes responsible for animal multicellularity within these protists, they help elucidate the nature of the unicellular ancestor of animals.
Holozoa is the most inclusive clade containing Homo sapiens (a metazoan), but not Neurospora crassa (a fungus). It is a clade with a branch-based definition: it contains all the closest relatives to animals that aren't fungi, as well as their common ancestor. The clade was first discovered through phylogenetic analyses in 2002. These mostly unicellular relatives are the protist lineages of choanoflagellates, filastereans, ichthyosporeans, and three independent species Corallochytrium, Syssomonas and Tunicaraptor.
Choanoflagellata (>250 species) are the protists most closely related to animals. They are free-living unicellular or colonial flagellates that feed on bacteria using a characteristic “collar” of microvilli. This collar strongly resembles the collar cells of sponges; because of this, choanoflagellates were theorized to be related to sponges even in the 19th century. The mysterious Proterospongia is an example of a colonial choanoflagellate that was thought to be related to the origin of sponges. The affinities of the other single-celled holozoans only began to be recognized in the 1990s.
Ichthyosporea or Mesomycetozoea (~40 species) are mostly parasites or commensals of a wide variety of animals, including humans, fish and marine invertebrates. Most reproduce through multinucleated colonies and disperse as flagellates or amoebae.
Filasterea is a group composed by the amoeboid genera Ministeria, Pigoraptor and Capsaspora, united by the structure of their thread-like pseudopods.
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The eukaryotes constitute the domain of Eukaryota (juːˈkærioʊts,_-əts), organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms are eukaryotes. They constitute a major group of life forms, alongside the two groups of prokaryotes, the Bacteria and the Archaea. Eukaryotes represent a small minority of the number of organisms, but due to their generally much larger size, their collective global biomass is much larger than that of prokaryotes.
The apusomonads (order Apusomonadida) are a group of protozoan zooflagellates that glide on surfaces, and mostly consume prokaryotes. They are of particular evolutionary interest because they appear to be the sister group to the Opisthokonts, the clade that includes both animals and fungi. Together with the Breviatea, these form the Obazoa clade. Apusomonads are small gliding heterotrophic biflagellates (= with two flagella) that possess a proboscis, formed partly or entirely by the anterior flagellum surrounded by a membranous sleeve.
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, the term "flagellate" is included in other terms (such as "dinoflagellate" and "choanoflagellata") which are more formally characterized.
Delves into the movement of motile unicellular organisms and the concept of morphing structures inspired by them.
Explores the evolution and function of protein-repair machineries, emphasizing the role of ATP-fueled unfolding machines in preventing protein aggregation and promoting proper folding.
Explores protein disaggregation by the Hsp70 chaperone system and the significance of aggregate modification for protein refolding.
The ratio of nuclear content to cytoplasmic volume (N/C ratio) is a key regulator driving the maternal-to -zy-gotic transition in most animal embryos. Altering this ratio often impacts zygotic genome activation and de-regulates the timing and outcome of em ...
In animals, cell-matrix adhesions are essential for cell migration, tissue organization, and differentiation, which have central roles in embryonic development [1-6]. Integrins are the major cell surface adhesion receptors mediating cell-matrix adhesion in ...
CELL PRESS2020
Significant increases in sedimentation rate accompany the evolution of multicellularity. These increases should lead to rapid changes in ecological distribution, thereby affecting the costs and benefits of multicellularity and its likelihood to evolve. How ...