Unikonts

OLD Audio recording

Video recording (.mov format, 0.4Gbytes)
Video recording (480p .mp4 format, 0.1Gbytes)
Video recording (1080p .mp4 format, 0.3Gbytes

 

  • Unikonts
    • Amoebozoa
      • Archamoeba (amitochondrial parasitic amoeba)
      • Lobosea (typical amoeba)
      • Myxogastrids (acellular slime molds)
      • Distyostelids (cellular slime molds)
      • Protostelids (sometimes called “primitive” slime molds)
    • Opisthokonta
      • Fungi
        • Ascomycetes (Sac fungi, mycorrhizal fungi, yeast, fission yeast)
        • Bacidiomycetes (mushrooms, rusts, smuts, and Cryptococcus)
        • Zygomycetes (common molds)
      • Microsporidia (unicellular intracellular parasites of animals)
      • Chytrids (water molds)
      • Nucleariids (an amoeba with fine, thread-like pseudopods)
      • Mesomycetozoa (nondescript animal parasites)
      • Choanoflagellates (single or colonial flagellates that look like sponge cells)
      • Metazoa (multicellular animals)

About this Superkingdom

The Unikonts can be divided into two major subgroups: the amoebozoans (amoebas with large pseudopods, and slime molds) and opisthokonts (fungi, animals, and some unicellular relatives). All have mitochondria with flattened cristae, and typically have a single flagellum or are amoeboid with no flagella.

Amoebozoa

The amoeba phenotype has apparently arisen many times in eukaryotic evolution, but this group contains most of those that contain robust pseudopods, and in which the amoeboid morphotype predominates their life cycle; i.e. the organisms readily identifiable as “amoebas”. Also in this group are the slime molds; both the cellular slime molds (composed of individual amoeboid cells) such as Dictyostelium, and the acellular slime molds (a syncytial mass; many nuclei in a common cytoplasm) such as Physarum.

Example species : Physarum polycephum

Physarum
from wikicommons : http://commons.wikimedia.org/wiki/File:Slime_Mold_(Physarium_polycephalum).jpg

Also known as the “many-headed” or “yellow” slime mold, this common forest inhabitant feeds on saprophytically on microbes. It is an “acellular” slime mold, with a multinucleate syncytial cytoplasm. Haploid spores germinate to produce swarmer gametes. Two flagellated gametes fuse to form a diploid cell, which transforms into an amoeboid, which grows by enlargement with nuclear division but no cytoplasmic division. Individual plasmodia can become quite large, and because they are brightly colored are conspicuous. Upon starvation, the plasmodium produced stalked sporangia, and after meiosis haploid spores are released into the wind. Amazingly, these organisms are capable of learned behavior, including solving mazes and anticipation of repetitive events.

Opisthokonts

The Opisthoconts include the fungi, animals, and some unicellular relatives of each that are often not considered to be either fungi or animals.

The groups related to fungi include the Microsporidia, Chytrids, and nuclearids. Microsporidia are spore-forming unicellular intracellular parasites primarily of insects. Human infections are usually opportunistic. Chytrids are often unicellular, but some are water molds. One species, Batrachochytrium dendrobatidis, is responsible for devastating declines in amphibian populations worldwide. Nucleariids are obscure amoeboid soil and aquatic organisms with fine, needle-like pseudopods.

The unicellular relatives of animals are the choanoflagellates and mesomycetozoans. Choanoflagellates are either individual or colonial flagellates, with a single terminal flagellum an a surrounding circle of about 3 dozen microvilli. Cells are often imbedded in an extracellular polysaccharide matrix and/or loose shells of silica. In many ways, the choanoflagellates might resemble primitive sponges. Mesomycetozoans are obscure and non-description fish parasites.

Example species:

Sphyraena barracuda

Great Barracuda
James W. Brown - off Middle Caicos Island

The barracuda is a large metazoan, reaching a size of up to approximately 2 x 10^6 microns. It is heterotrophic, as are all metazoans, feeding carnivorously (mostly as a scavenger) on other teleosts. Often considered dangerous, this reputation is undeserved; although common and curious, attacks on humans in the water are unsubstantiated. However, humans are often injured by barracuda when taken by spear or hook and line. Although a popular food item in many parts of the world, eating large barracuda can result in ciguatera poisoning.

Saccharomyces cerevisiae

yeast
from Wikicommons : http://commons.wikimedia.org/wiki/File:S_cerevisiae_under_DIC_microscopy.jpg

A familiar budding yeast, commonly used in baking, brewing, and wine-making. Yeast are saparophytic heterotrophs (as are fungi generally), and can grow either aerobically by oxidative respiration, or anaerobically by fermentation. Cells can exist either as haploid or diploid in culture, or a mixture of the two. Reproduction is by budding, and diploid cells when starved undergo meiosis to produce 4 haploid spores. Growing haploids can be either of a or α mating type, and an a/α pair will fuse to form a diploid. Although typically unicellular, yeast can sometimes be seen to grow as pseudohyphae.