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Protists Chapter 28
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Outline Endosymbiosis Classifying Protists General Biology of Protists Six Lineages Euglenozoa Alveolata Stramenopila Rhodophyta Chlorophyta Choanoflagellida
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Endosymbiosis Theory of endosymbiosis proposes that mitochondria originated as symbiotic, aerobic bacteria. Each mitochondrion has its own genome in a circular, closed molecule of DNA. divide by simple fission directed by nuclear genes
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Theory of Endosymbiosis
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Classifying Protists Protists are the most diverse of the four kingdoms in the domain Eukarya. artificial group of convenience single-celled organisms little consensus about classification
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Protist Classification
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General Biology of the Protists
Cell surface possess varied array of cell surfaces Locomotor organelles chiefly flagellar rotation or pseudopodial movement Cyst formation dormant form of a cell with resistant outer covering in which metabolism is essentially shut down
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General Biology of the Protists
Nutrition employ all forms but chemoautotrophic phototrophs heterotrophs phagotrophs - visible food particles osmotrophs - food in soluble form
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General Biology of the Protists
Reproduction typically reproduce asexually binary fission - equal halves budding - progeny cell smaller schizogony - multiple fission sexual reproduction in times of stress gametic meiosis - before gametes zygotic meiosis - after fertilization intermediary meiosis - alternating
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Protists Six identified lineages: Euglenozoa Alveolata Stramenopila Rhodophyta Chlorophyta Choanoflagellida
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Euglenozoa Euglenoids most are freshwater about one-third are autotrophic pellicle lies within membrane stigma - light sensitive organ that aids in orienting toward light Euglena two flagella attached to reservoir contain numerous chloroplasts
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Euglenoids
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Euglenozoa Kinetoplastids unique, single mitochondrion in each trypanosome Trypanosomes are kinetoplastids that cause many serious human diseases. African sleeping sickness Chagas
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Alveolata Dinoflagellates distinctive flagella, protective coats, and biochemistry reproduce primarily by asexual cell division responsible for “red tides”
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Alveolata Apicomplexes spore-forming animal parasites unique arrangement of fibrils, microtubules, vacuoles, and other cell organelles malarial parasite - Plasmodium malaria eradication eliminating mosquito vectors poison parasites inside human body develop vaccines
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Plasmodium Life Cycle
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Alveolata Ciliates most feature large numbers of cilia usually arranged in longitudinal rows or spirals around the body form vacuoles to ingest food and regulate water balance waste emptied through cytoproct Paramecium
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Paramecium
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Stramenopila and Rhodophyta
includes brown algae, diatoms, and oomycetes brown algae - conspicuous seaweeds alternation of generations diatoms (phylum Chrysophyta) - photosynthetic, unicellular organisms with double shells of opaline silica
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Brown Algae
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Stramenopila and Rhodophyta
oomycetes (water molds) - parasites or saprobes. comprise water molds, white rusts, and downy mildews motile zoospores bear two unequal flagella life cycles characterized by gametic meiosis and a diploid phase
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Stramenopila and Rhodophyta
Red algae range in size from microscopic to very large. origin a source of controversy tentatively treated as a sister clade of green algae (Chlorophyta)
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Chlorophyta Green algae are the ancestors of the plant kingdom. extensive fossil record dating back 900 million years mostly aquatic Chlamydomonas well-known genus probably represents primitive state Chlorophyta did not give rise to land plants.
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Chlamydomonas Life Cycle
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Choanoflagellida Choanoflagellates are most like the common ancestor of the sponges. contain a single emergent flagellum surrounded by a funnel-shaped, contractile collar
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Amoebas contain pseudopods that can form at any point on the cell body and can move in any direction Phylum Actinopoda (radiolarians) secrete glassy exoskeletons of silica.
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Foraminifera heterotrophic marine protists with pore-studded shells complex life cycle with alternation between haploid and diploid generations
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Slime Molds Slime molds originated at least three distinct times. plasmodial slime molds stream along as a non-walled, multinucleate mass of cytoplasm, plasmodium produces sporangium during times of resource shortage forms spores that quickly undergo meiosis
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Slime Molds Cellular slime molds individual organisms behave as separate amoebas, moving through soil or other substrate and ingesting bacteria individual organisms aggregate and form moving mass “slug” when food becomes scarce
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Cellular Slime Mold Development
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Summary Endosymbiosis Classifying Protists General Biology of Protists Six Lineages Euglenozoa Alveolata Stramenopila Rhodophyta Chlorophyta Choanoflagellida
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