Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Kingdom Protista • Characteristics – – – – – – Algaelike or plantlike Protozoa or Animallike Funguslike Unicellular Multicellular Eukaryotes Kingdom Protista Algaelike or Plantlike • All obtain energy by photosynthesis. • All have chlorophyll a, but may have various other chlorophylls and different accessory pigments. • Phyla – Euglenophyta • One to three flagella, at their apical (leading) end – Dinoflagellates • Two flagella- one is posterior, while the second is transverse and rest in an encircling mid groove perpendicular to the first flagellum. • Some are bioluminescent. • Others produce nerve toxins that concentrate in filter-feeding shellfish, which then cause illness in human when eaten. Kingdom Protista Algaelike or Plantlike • Phyla – Chrysophyta • Golden algae • Have one or two apical flagella – Diatoms • Shells made of silica (SiO2) – Chlorophyta • • • • • • Green algae Have both chlorophyll a and b Cellulose cell walls Store their carbohydrates as starch Believed to be the ancestors of plants Variation in sexuality. Kingdom Protista Algaelike or Plantlike • Phyla – Phaeophyta • • • • Brown algae Multicellular Have flagellated sperm cells. Some are giant seaweeds or kelps Kingdom Protista Protozoa or Animallike • Heterotrophs – Consume either living cells (being predatory or parasitic) or dead organic matter. • Phyla – Rhizopoda • Amoebas • Move by extensions of their of their cell body called pseudopodia. • Pseudopodia encircle food and absorb it by phagocytosis Kingdom Protista Protozoa or Animallike • Phyla – Zooflagellates • Flagellated protozoa • Some mutualistic species digest cellulose in the guts of termites. • Others are parasites, such as Trypanosoma, which is transmitted by the tsetse fly and cause African sleeping sickness in humans. Kingdom Protista Protozoa or Animallike • Phyla – Sporozoa • Parasites of animals • No physical means of motility • They form spores which are dispersed by one or more hosts that participate in the completion of their life cycle • Sporozoan that causes malaria, spends part of its life cycle in mosquitoes and part in humans. Kingdom Protista Protozoa or Animallike • Phyla – Ciliophora • Distinguished by their cilia, which they use for moving. • Specialized structures – – – – Mouth Anal pore Contractile vacuoles for water balance Two kinds of nuclei (macronucleus and several small micronuclei) • Paramecium Kingdom Protista Funguslike • Resemble fungi because they form either filaments or spore-bearing bodies similar to fungi. • Three divisions: Kingdom Protista Funguslike • Acrasiomycota (cellular slime molds) – Exhibit both funguslike and protozoalike characteristics during their life cycle. – Spores germinate into amoebas which feed on bacteria. – When food sources are depleted, the amoebas aggregate into a single unit, which migrates as a slug. – The individual cells of the slug then mobilize to form a stalk with a capsule at the top similar to the sporebearing bodies of many fungi. – Spores are then released, which repeat the cycle when they germinate. Kingdom Protista Funguslike • Myxomycota (plasmodial slime molds) – Grow as a single, spreading mass (plasmodium) feeding on decaying vegetation. – When food becomes unavailable or when the environment desiccates, stalks bearing spore capsules form. – Haploid spores released from the capsule germinate into haploid amoeboid or flagellated cells which fuse to form a diploid cell. – The diploid cell grows into the spreading plasmodium. Kingdom Protista Funguslike • Oomycota (water molds, downy mildew, and white rust) – They are either parasites or saprobes. – They are much like fungi in that they form filaments (hyphae) which secret enzymes that digest the surrounding substances. – The breakdown products of digestion are then absorbed. Kingdom Protista Evolution of Eukaryotes • Cellular structures and processes unique to eukaryotes: – – – – – – Membrane-enclosed nucleus Mitochondria Chloroplasts Endomembrane system Cytoskeleton Multiple chromosomes consisting of linear DNA molecules compactly arranged with proteins. – Life cycles that include mitosis, meiosis, and sex. Kingdom Protista Evolution of Eukaryotes • First process in eukaryotic evolution: – Specialized infoldings of the prokaryotic plasma membrane, may have produced: • Nuclear envelope • Endoplasmic reticulum • Golgi apparatus Kingdom Protista Evolution of Eukaryotes • Second process in eukaryotic evolution: – Endosymbiosis hypothesis, Lynn Margulis, University of Massachusetts • Probably led to the mitochondria and chloroplast • Proposes that mitochondria and chloroplast were formerly small prokaryotes living within larger cells. • Proposed ancestors of mitochondria were aerobic heterotrophic prokaryotes that became endosymbionts. • Proposed ancestors of chloroplasts in early eukaryotes were photosynthetic prokaryotes, probably cyanobacteria, that became endosymbionts. Kingdom Protista Evolution of Eukaryotes • Evidence (mitochondria/chloroplast to bacteria) – Endosymbiotic relationships in the modern world. – Appropriate size – Inner membranes have several enzymes and transport systems that resemble those found on the plasma membrane of modern prokaryotes. – Replicate by a splitting process similar to binary fission in bacteria. – Contain a genome consisting of circular DNA not associated with histones or other proteins. Kingdom Protista Evolution of Eukaryotes • Evidence (mitochondria/chloroplast to bacteria) – Contain transfer RNA, ribosomes, and other items needed to transcribe and translate their DNA into proteins. – Ribosomes are more similar to prokaryotic ribosomes. • Size • Biochemical characteristics • Sensitivity to certain antibiotics – Lang and Burger, University of Montreal • Found that mitochondrial genome of the protist Reclinomonas americana closely matches that of bacteria in structure and function.