This chapter explain why the kingdom Protista is no longer considered a legitimate taxon; explain the process of endosymbiosis and state what living organisms are likely relatives of mitochondria and plastids; distinguish between endosymbiosis and secondary endosymbiosis; name the five supergroups, list their key characteristics, and describe some representative taxa. | Chapter 28 Protists Overview: A World in a Drop of Water Even a low-power microscope Can reveal an astonishing menagerie of organisms in a drop of pond water Figure 50 m These amazing organisms Belong to the diverse kingdoms of mostly single-celled eukaryotes informally known as protists Advances in eukaryotic systematics Have caused the classification of protists to change significantly Concept : Protists are an extremely diverse assortment of eukaryotes Protists are more diverse than all other eukaryotes And are no longer classified in a single kingdom Most protists are unicellular And some are colonial or multicellular Protists, the most nutritionally diverse of all eukaryotes, include Photoautotrophs, which contain chloroplasts Heterotrophs, which absorb organic molecules or ingest larger food particles Mixotrophs, which combine photosynthesis and heterotrophic nutrition Protist habitats are also diverse in habitat And including freshwater and marine species Figure –d 100 m 100 m 4 cm 500 m The freshwater ciliate Stentor, a unicellular protozoan (LM) Ceratium tripos, a unicellular marine dinoflagellate (LM) Delesseria sanguinea, a multicellular marine red alga Spirogyra, a filamentous freshwater green alga (inset LM) (a) (b) (c) (d) Reproduction and life cycles Are also highly varied among protists, with both sexual and asexual species A sample of protist diversity Table Endosymbiosis in Eukaryotic Evolution There is now considerable evidence That much of protist diversity has its origins in endosymbiosis The plastid-bearing lineage of protists Evolved into red algae and green algae On several occasions during eukaryotic evolution Red algae and green algae underwent secondary endosymbiosis, in which they themselves were ingested Cyanobacterium Heterotrophic eukaryote Primary endosymbiosis Red algae Green algae Secondary endosymbiosis Secondary endosymbiosis Plastid Dinoflagellates Apicomplexans Ciliates Stramenopiles Euglenids . | Chapter 28 Protists Overview: A World in a Drop of Water Even a low-power microscope Can reveal an astonishing menagerie of organisms in a drop of pond water Figure 50 m These amazing organisms Belong to the diverse kingdoms of mostly single-celled eukaryotes informally known as protists Advances in eukaryotic systematics Have caused the classification of protists to change significantly Concept : Protists are an extremely diverse assortment of eukaryotes Protists are more diverse than all other eukaryotes And are no longer classified in a single kingdom Most protists are unicellular And some are colonial or multicellular Protists, the most nutritionally diverse of all eukaryotes, include Photoautotrophs, which contain chloroplasts Heterotrophs, which absorb organic molecules or ingest larger food particles Mixotrophs, which combine photosynthesis and heterotrophic nutrition Protist habitats are also diverse in habitat And including freshwater and marine species Figure .
