Biol 165: Diversity of Life 2013-04-21 2:36 PM
• Protists are a paraphyletic group (ie, even some algae are included
in the group).
• DNA/RNA studies indicate that it is a complicated group comprised
of serial endosymbiotic events.
• most methods of classifying them prove to be inconvenient and not
easily accommodating to their differences.
• each phylocode solves some problems while creating others.
• Protists can be found in each of the 6 Eukaryote Supergroups:
o SuperGroup Opisthokonta
o SuperGroup Chromalveolata
o Supergroup Planta
• The 3 groups of “primitive” Protozoan (unicellular eukaryote)
o SuperGroup Amoebozoa (amoebae and slime molds)
o SuperGroup Excavata (basal flagellates)
o SuperGroup Rhizaria
• Is a primitive kind of protist
• They move using pseudopodia, and the mode of travel is called
• They obtain food by phagocytosis
• giant, and free-living
• multinucleate and herbivorous
• most primitive protist known; it lacks most organelles
Other Species: Phylum Rhizopodia
• Amoeba proteus o large and carnivorous
o common in fresh water, and even cracks in pavement
• Entamoeba histolytica
o causes Amoebic dysentery
Cell Division: 3 Kinds
o the nuclear membrane and nucleolus remains intact.
o Chromosomes are not clear.
o nuclear membrane is intact, but nucleolus disintegrates
o there are no centrioles, and spindle fibres terminate at
o typical mitosis occurs including nuclear membrane loss
o spindle fibres converge and operate w/o centrioles
o chromosomes are recognizable.
Cellular “Slime Molds”
• ie, Phylum Acrasea and Phylum Dictyotstelida
• Cellular slime molds spend most of their life cycle as free living
individual haploid protists.
• Only when food is scarce do they aggregate to form a sporangium
to release microcysts.
• The new microcysts release amoeboid cells, which can fuse to for a
• The macrocyst will then divide by meiosis to produce two haploid,
free-living amoeboid daughter cells.
• Cellular Slime Molds have a heteromorphic life cycle – different
appearances during life cycle.
Plasmodial Slime Molds (PSM)/Acellular Slime Molds
• Phylum Myxostelida
• Genus Stemonitis and Lycogala
• PSM are enormous single cells with thousands of nuclei • They are formed by the fusion of numerous individual flagellated
• They also form sporangia/fruiting bodies, and disperse spores.
SuperGroup Excavata – Basal Flagellates
• considered to be the most primitive of protists
• many are disease causing, or parasitic
• ie, Chagas disease, African Sleeping Sickness, leishmaniasis, some
o Phylum Amoebgoflagellata
o have both amoeboid and flagellate stages in life cycle
o amoeboid stage lives in soil, normally only stage that can
o flagellated stage lives in pools of water