Domain Eukarya Kingdom Protista (AKA: Kingdom of Confusion!)

 Organisms in this kingdom may be algaelike, animallike, funguslike, unicellular, or multicellular.  Evolutionary relationships among the groups are very weak, poorly understood or both.  This is a kingdom of convenience for biologists—and confusion!

 Features shared by two or more groups in the Protista kingdom (such as flagella or chloroplasts) do not mean they are evolutionarily related.  These may represent convergent evolution— the features arose in the groups independently. Both of these species of protozoans have flagella, but they are not related.

 Plant-like protists all obtain energy by photosynthesis  All have chlorophyll a but may have various other chlorophylls and accessory pigments.  They are categorized by: type of pigments, form of carbohydrates they store, number of flagella, and type of cell wall. Euglena Chlorophyta Dinoflagellates Diatoms Volvox

 Euglenoids have one to 3 flagella.  Instead of a cellulose cell wall (like plants), they have thin protein strips called pellicles that wrap over their cell membranes.  They can become heterotrophs in the absence of light. Many Euglenas have an eyespot that permits phototaxis —the ability to move in response to light.

 Dinoflagellates have two flagella. (one is posterior, the 2 nd is transverse and rests in an encircling mid groove perpendicular to the 1 st )  Some of these are bioluminescent.  Some produce nerve toxins that concentrate in filter-feeding shellfish, causing illness in humans who eat them.

When certain species of dinoflagellates reproduce rapidly, their populations can produce a phenomenon called Red Tides. These can be harmful to shellfish and fish that live in these waters, both by producing toxins and depleting the oxygen concentrations. This can cause massive fish kills.

 Diatoms have tests (shells) that fit together like a box with a lid.  The tests are made of silica—the same material as glass.  They are important producers in aquatic ecosystems.

 This group of protists are multicellular.  They have sperm cells with flagella which swim in the water.  Some species are giant seaweeds, or kelp.  They are very important in marine ecosystems – both as producers and for the habitat they provide for fish and other species.

 Rhodophyta, or red algae, contain red accessory pigments called phycobilins.  They are multicellular.  Their gametes do not have flagella.  They are important producers in marine ecosystems.

 Chlorophyta, or green algae, have both chlorophyll a and b  They have cellulose cell walls like plants  They store their carbohydrates as starch, like plants  Most are single-celled, but some can live in colonies.  They are believed to be the ancestors of plants.

 The protozoa, or animal-like protists are heterotrophs.  They consume either living cells (thus being predatory or parasitic) or dead organic matter. Stentor—a protozoan that feeds by swirling its cilia and sweeping in small prey.

 Rhizopoda are amoebas  They move by extensions of their cell body called pseudopodia.  Pseudopodia encircle food and absorb it by phagocytosis.

 Foraminifera, or forams, have tests (shells) made of calcium carbonate (the same material that make up the shells of shellfish)  Many ancient marine sediments consisting of certain foram tests are good indicators of underlying oil deposits.

 Apicomplexans are parasites of animals  They are characterized by an apical complex—a complex of organelles located at one end of the cell.  They have no physical means of motility.  They form spores which are dispersed by hosts that participate in the completion of their life cycle. Malaria is one of the most serious human diseases in the world— killing almost 1 million people per year. Plasmodium —a sporozoan that spends part of its life cycle in mosquitos and part in humans. Plasmodium in red blood cells

 Ciliates are distinguished by their cilia, which they use for moving and other functions.  Because of their specialized structures, they are perhaps the most complex of all cells.  Paramecium is this phylum’s most notable member.

 Fungus-like protists resemble fungi because they form either filaments or spore-bearing bodies similar to the fungi.

 Cellular slime molds exhibit both fungus-like and protozoa-like characteristics.  Spores germinate into amoebas which feed on bacteria.  When food sources are depleted, the amoebas aggregate into a single unit, which emerges as a slug.

 When food runs out and they are ready to form sporangia,  They release signal molecules into their environment, by which they find each other and create swarms.  These amoeba then join up into a tiny multicellular slug-like coordinated creature, which crawls to an open lit place and grows into a fruiting body. Some of the amoebae become spores to begin the next generation, but some of the amoebae sacrifice themselves to become a dead stalk, lifting the spores up into the air.

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 Plasmodial slime molds grow as a single, spreading mass (or plasmodium)  They feed on decaying vegetation.  When food becomes unavailable or when the environment dries up, stalks bearing spore capsules form. Haploid cells released from the capsule germinate into haploid amoeboid or flagellated cells, which fuse to form a diploid cell. The diploid cell grows into the spreading plasmodium.

Physarum shown here, are basically enormous single cells with thousands of nuclei. They are formed when individual flagellated cells swarm together and fuse. The result is one large bag of cytoplasm with many diploid nuclei.

 Oomycota include the water molds, downy mildews, and white rusts.  They are either parasites or saprobes (eat dead organic material)  They are much like fungi in that they form filaments (hyphae) which secrete enzymes that digest the surrounding substances.  Their filaments, however, lack septa (cross walls) so their cells contain many nuclei within a single cell.  Also, their cell walls are made of cellulose (like plants) instead of chitin (like fungi). Downy Mildew on grapes White rust Water mold