28_Lectures_2008_Class

28_Lectures_2008_Class - Chapter 28 Protists Key Concepts...

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Unformatted text preview: Chapter 28 Protists Key Concepts • 28.1 Most Eukaryotes are single-celled organisms • 28.2 Excavates are include protists with modified mitochondria and protists with unique flagella • 28.3 Chromalveolates may have originated by secondary endosymbiosis • 28.4 Rhizarians are a diverse group of protists defined by DNA similarities • 28.5 Red and green algae are the closest relatives of land plants • 28.6 Unikonts include protists that are closely related to fungi and animals • 28.7 Protists play key roles in ecological relationships 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 Life in a drop of water Fig. 28-01 1 µm 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 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 http://www.uog.edu/dns/Lobban.htm • Protists are also diverse in habitat, including freshwater and marine species QuickTime™ and a YUV420 codec decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. • 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 unicellular protozoan (LM) 100 µm 100 µm Ceratium tripos , a unicellular marine dinoflagellate (LM) 500 µm Delesseria Sanguinea , a multicellular 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 Endosymbiosis in Eukaryotic Evolution...
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28_Lectures_2008_Class - Chapter 28 Protists Key Concepts...

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