Chapter 20 The Diversity of Protists Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc Chapter 20 At a Glance 20 1 What Are Protists 20 2 What Are the Major Groups of Protists Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Most protists are single celled Protists include any eukaryote that is not a plant animal or fungus Most protists are single celled and microscopic in size Some are large aggregations or colonies of single celled individuals others are multicellular organisms Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Protists use diverse modes of nutrition They may ingest food They may absorb nutrients from their surroundings They may exhibit photosynthesis Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Protists use diverse modes of nutrition continued Protists that ingest food are typically predators They use extensions of the cell membrane called pseudopods to surround and engulf prey items Other predatory protists create tiny currents that sweep food particles into mouth like openings in the cell Food is typically contained in a membrane surrounded food vacuole for digestion Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Protists use diverse modes of nutrition continued Protists that absorb nutrients directly from the surrounding environment are of two types Free living types in the soil that decompose organic dead matter Parasites that live inside the bodies of other organisms sometimes harming the host Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Protists use diverse modes of nutrition continued Some protists have photosynthetic organelles called chloroplasts Photosynthetic protists are abundant in oceans lakes and ponds They are free floating They sometimes live in mutually beneficial associations with other organisms Solar energy captured by the protist is used by the host which in turn shelters and protects the protist Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Protists use diverse modes of nutrition continued Photosynthetic protists are collectively known as algae Single celled non photosynthetic protists are collectively known as protozoa Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Protists use diverse modes of reproduction Most protists reproduce asexually by mitotic cell division Some also reproduce sexually Two individuals contribute genetic material to an offspring that is genetically different from either parent Many protists reproduce asexually but adopt sexual reproduction during certain times of the year or under stressful circumstances e g a crowded environment or a food shortage The details of sexual reproduction in protists vary considerably but never includes the formation and development of an embryo as occurs in plants and animals Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Protists use diverse modes of reproduction continued Nonreproductive processes that combine the genetic material of different individuals are also common among protists Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Protists affect humans and other organisms Their ecological role of photosynthetic marine protists algae has a positive impact They capture solar energy and make it available to other organisms is the ecosystems They release oxygen gas Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 1 What Are Protists Protists affect humans and other organisms continued As the source of many human and plant diseases the protists have a negative impact Parasitic protists cause some of humanity s most prevalent ailments and some of its deadliest afflictions Protists also cause plant diseases some of which attack crops important to humans Some marine protists release toxins that can accumulate to harmful levels in coastal areas Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 2 What Are the Major Groups of Protists Excavates have a feeding groove and lack mitochondria They have 2 nuclei and move about by multiple flagella They are named for the feeding groove that gives the appearance of having been excavated from the surface of the cell The two largest groups are the diplomonads and the parabasalids Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 2 What Are the Major Groups of Protists Excavates have a feeding groove and lack mitochondria continued The diplomonads have two nuclei and move about by multiple flagella The parasitic diplomonad Giardia found in freshwater streams infects human and other mammalian hosts causing gastrointestinal disorders Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 2 What Are the Major Groups of Protists Excavates have a feeding groove and lack mitochondria continued Giardia exist as cysts a stage of their life cycle in the feces of animals When excreted the cysts enter water systems and if ingested develop into adult diplomonads In humans the adults can cause severe diarrhea dehydration nausea vomiting and cramps Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 2 What Are the Major Groups of Protists Excavates have a feeding groove and lack mitochondria continued Parabasalids are anaerobic flagellated protists named for the presence in their cells of a distinctive structure called the parabasal body Parabasalids in the gut of termites digest the wood the termites eat Another parabasalid Trichomonas vaginalis causes the sexually transmitted infection trichomoniasis in humans Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 2 What Are the Major Groups of Protists Euglenozoans have distinctive mitochondria continued Kinetoplastids derive their name from the arrangement of their DNA into structures called kinetoplasts Most kinetoplastids possess at least one flagellum that may propel the organism sense the environment or ensnare food Kinetoplastids may be free living in soil or water or live inside other animals A dangerous kinetoplastid is Trypanosoma which is responsible for African sleeping sickness that is transmitted to humans by infected tsetse flies Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 20 2 What Are the Major Groups of Protists
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