The group of Protists represents an unusual mix of organisms The organisms found in this group are all eukaryotes and most are single celled for most of their life cycle Eukaryotes have Since the organisms of this group Protists are made up of eukaryotic cells they are clearly different from the Bacteria and Archaea they have a nucleus with a double membrane 2 or more chromosomes linear DNA organelles Past classifications of the protists organized them into three general groups based on nutritional methods Plant like protists Autotrophic photsynthetic Fungus like protists Heterotrophic decomposers Animal like protists Heterotrophic hunters and symbiotic so they ingest their food absorb nutrients or capture solar energy Phytoplankton are the photosynthetic eukaryotes at the base of most aquatic food webs Marine phytoplankton are responsible for 70 of the photosynthesis and most of the oxygen production of the planet Algae are the photosynthethic protists Protozoans are heterotrophic protists which actively seek and ingest their food either food particles or other organisms Most protists can be organized into eight general groups see table 20 1 However there is a good deal of uncertainty about the evolution of these groups The classification of the protists is a work in progress Why the uncertainty about the classification of these groups Because some species were grouped together because they had physical similarities but were actually from different lineages and others with little physical likeness sometimes shared a common ancestor Excavates move via flagella have a feeding groove excavated heterotrophic and lack mitochondria The two largest subgroups of the excavates are the diplomonads and the parabasalids Diplomonads Parabasalids both free living and symbiotic species have 2 nuclei multiple flagella an example Giardia is a member of this group Makes you have diarrhea and get cysts Trichomanas vaginalis is a sexually transmitted member of this group males can often be asymptomatic Aerobic large group of flagellated protozoans lack a rigid covering Single celled some are mutualists others are parasitic ex Trichomonas vaginalis an STD There are two major groups the euglenids and the kinetoplastids Most are freshwater Have 1 3 flagella Primarily photosynthetic but can switch to heterotrophic in the dark Have a photoreceptor called an eyespot Named after Euglena Kinetoplastids Some of the symbiotic species are parasitic Including Trypanosoma causing sleeping sickness Stramenopiles aka Chromists Form a clade with shared ancestry Are many different forms But all have fine hair like projections on their flagella that may only be present in certain stages Most single celled some living as multicellular colonies mixed nutritional methods Euglenozoans Euglenids Water molds Diatoms long filamentous individuals group to form many are heterotrophic decomposers cottony tufts Brown Algae Water molds they form a small division Impacts on humans Potato late blight Downy mildew in grapes One common water mold with economic importance is downy mildew Diatoms Brown Algae Marine Alveolates Deep water to tidal Brown color caused by accessory pigments Cells can form large aggregated Giant kelp forest Gas bladders to keep the plant extending toward the surface colonies Alveolates parasites predators and phytoplankton most live as single cells mixed nutritional methods including varied forms of motility how they get around parasitic forms Dinoflagellates Apicoplexans a k a Sporozoans Ciliates Dinoflagellates Most are marine 2 flagella one at the end and one in Most are photosynthetic May have a cellulose cell wall Many are bioluminescent give off a blue glow when disturbed an equatorial groove Apicoplexans a k a Sporozoans Phylum Apicomplexa All are heterotrophic parasites which have a non adult mobile stage called a Sporozoite Plasmodium that causes malaria Toxoplasma that vectors through cats comes from cat poop gets people sick These cilia may be a uniform covering of the organism or can be localized in patches The ciliates are the most complex of the protozoa with an internal structure that includes an oral groove an anal pore a contractile vacuole and two types of nuclei Ciliates are unicellular live in freshwater heterotrophic and are used for movement and feeding These two different nuclei have different functions Rhizarians most live as single cells external shells of various types heterotrophic motility based on very thin pseudopodia means false legs little narrow extensions from cells Includes foraminiferans or forams and radiolarians Foraminiferans Radiolarians calcium carbonate shells marine shell morphology form limestone deposits when they sink and die external glass shell silica pseudopods extend through shells shell morphology form radiolarian ooze when they sink and die Amoebozoans have many different forms aquatic or terrestrial some living as multicellular colonies heterotrophic move using pseudopodia either decomposers or predators There are three major groups Amoebas Acellular slime molds Cellular slime molds Amoebas a k a lobose amoebas move and engulf food using pseodopodia Most are free living though some can be parasitic ex amoebic Slime molds live on forest floor The two basic stages of slime molds are Acellular slime molds dysentery they are also known as plasmodial slime molds This name comes from the plasmodium which is the mobile feeding stage of this organism life cycle in the mobile stage the cells go through mitosis but not cytokinesis the result is an acellular organism which looks like a very large multi nucleated single cell This plasmodium moves through decaying material engulfing bacteria and food particles In harsh environmental conditions dry the plasmodium forms a mound and produces a stalked fruiting body that produces haploid spores Cellular slime molds The characteristics of the cellular slime molds they have a two part life cycle in which the cells of many individuals form an interactive aggregate which is almost multicellular Individual solitary cells characterize the mobile feeding stage Amoeboid movement using pseudopodia when food is scarce cells form a pseudoplasmodium which is a false plasmodium During times of environmental stress a signal causes the cells aggregate into a pseudoplasmodium but remain individual cells This aggregate of cells is still mobile and migrates to a suitable spot for the formation of the fruiting body The characteristics of
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