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Chapter 28

Chapter 28. Protists. Protists. Ancestors to modern protists , plants, animals and fungi. Oldest known are 2.1 billion years old ( acritarchs ). Most DIVERSE eukaryotes Most are unicellular Most use cellular respiration

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Chapter 28

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  1. Chapter 28 Protists

  2. Protists • Ancestors to modern protists, plants, animals and fungi. Oldest known are 2.1 billion years old (acritarchs). • Most DIVERSE eukaryotes • Most are unicellular • Most use cellular respiration • Fall into 3 nutritional groups: ingestive (animal like), absorptive (fungus like) and photosynthetic (plant like) • Most are motile with cilia or flagella • Vary in reproductive/life cycles (some asexual, some sexual)

  3. Evolution of Eukaryotic Cell • SYMBIOSIS: mitochondria and chloroplasts were originally small prokaryotes in larger cells (serial endosymbiosis theory)

  4. Phylogeny: Difficult to classify • 1. Archaezoa: lack mitochondria • Question: Does their ancestry precede mitochondrial evolution??? • 3 subgroups: diplomonads, trichomonads, microsporidians

  5. 2. Euglenozoa: flagellates • Euglenoids: characterized by anterior pocket from which flagella emerge, mostly autotrophic • Kinetoplastids: single large mitochondrion and kinetoplast housing extranuclear DNA Ex. African tsetse fly: spreads Trypanosoma that causes African sleeping sickness.

  6. 3. Alveolata: small membrane bound cavities (alveoli) under cell surfaces. • Dinoflagellates: component of plankton found near the water surface, most are unicellular, perpendicular flagella causes spinning motion, episodes of population growth called blooms – cause red tides that may be toxic. (fish kill) • Apicomplexans: animal parasites. Ex. Plasmodium: causes malaria • Ciliates: uses cilia to move and feed, live along in fresh water. Cilia may cover all of cell or may be clustered. Two types of nuclei: 1 macronucleus that divides by binary fission and micronuclei that combine by SYNGAMY (union of two gametes) for genetic variation.

  7. Misc protists: • Rhizopods (amoebas): pseudopodia • Actinopods (helizoans): axopodia • Foraminiferans: marine, porous shell • Plasmoidial slime molds • Cellular slime molds

  8. Stramenophilia • Photosynthetic autotrophs and hetertrophs • Diatoms: yellow and brown, glasslike silica walls, reproduce asexually, live in plankton • Golden algae: yellow and brown carotene and xanophyll, biflagellated, live in plankton • Oomycota: water molds • Brown algae: multicellular, marine, brown pigments • SEAWEEDS: Thallus (Plantlike body), holdfast (rootlike), stipe (stemlike) and blades (leaflike) • Alternation of generations: diploid sporophyte releases haploid spores that develop into gametophyte, produces gametes that unite to make zygote that turns into diploid sporophyte.

  9. Rhodophyta • Red Algae: no flagella, many different pigments, most abundant in tropical oceans, alternation of generations is common

  10. Green Algae • Green chloroplasts, common ancestor with plants, mostly freshwater • Form “pond scum” • Most produce sexually

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