28 protists

28 protists - C h a p te r 2 8 Overview: Living Small Even...

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Chapter 28 Protists Overview: Living Small Even a low-power microscope can reveal a great variety of organisms in a drop of pond water Protist is the informal name of the kingdom of mostly unicellular eukaryotes Advances in eukaryotic systematics have caused the classification of protists to change significantly Protists are eukaryotes and thus have organelles and are more complex than prokaryotes Fig. 28-01 1 µ m Concept 28.1: Most Eukaryotes are single-celled organisms Protists are more diverse than all other eukaryotes and are no longer classified in a single kingdom Actually the Kingdom Protista was paraphyletic (of a group of organisms) descended from a common evolutionary ancestor or ancestral group, but not including all the descendant groups. some protist are actually more closely related to plants the Kingdom has been abandoned, but the term protist is still used to refer to eukaryotes that are neither plants, animals, nor fungi Most protists are unicellular, but there are some colonial and multicellular species Green algae Amoebozoans Opisthokonts Alveolates Stramenopiles Diplomonads Parabasalids Euglenozoans Dinoflagel ates Apicomplexans Ciliates Diatoms Golden algae Brown algae Oomycetes Excavata Chromalveolata Rhizaria Chlorarachniophytes Forams Radiolarians Archaeplastida Red algae Chlorophytes Charophyceans Land plants Unikonta Slime molds Gymnamoebas Entamoebas Nucleari ds Fungi Choanoflagel ates Animals Structural and Functional Diversity in Protists Protists exhibit more structural and functional diversity than any other group of eukaryotes Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell In multi-cellular organisms, some biological activity is relegated to tissue types, in unicellular protests they are carried out in sub-cellular organelles.
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Protists are also diverse in habitat, including freshwater and marine species Protists , the most nutritionally diverse of all eukaryotes, include: Photoautotrophs , which contain chloroplasts Plant-like Heterotrophs , which absorb organic molecules or ingest larger food particles Can be either: Animal-like (ingestive) Fungi-like (absorptive) Mixotrophs , which combine photosynthesis and heterotrophic nutrition same separations as above Protists are an extremely diverse assortment of eukaryotes The freshwater ciliate Stentor , a unicel ular protozoan (LM) 100 µ m 100 µ m Ceratium tripos , a unicel ular marine dinoflagel ate (LM) 500 µ m Delesseria Sanguinea , a multicel ular marine red alga Spirogyra , a filamentous freshwater green alga (insert LM) 4 cm http://www.micrographia.com/ http://biodidac.bio.uottawa.ca/ Reproduction and life cycles are also highly varied among protists, with both sexual and asexual species Reproduction Conjugation Binary fission Endosymbiosis in Eukaryotic Evolution There is now considerable evidence that much of
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28 protists - C h a p te r 2 8 Overview: Living Small Even...

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