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Kingdom Protista. KEY CONCEPTS. Protists are a diverse group of eukaryotic organisms, most of which are microscopic. Protista. Not a really valid “Kingdom” Few real evolutionary relationships Contains Algae : “plant-like” protists Protozoa : “animal-like” protists
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KEY CONCEPTS • Protists are a diverse group of eukaryotic organisms, most of which are microscopic
Protista • Not a really valid “Kingdom” • Few real evolutionary relationships • Contains • Algae: “plant-like” protists • Protozoa: “animal-like” protists • Slime & Water molds: fungal-like protists
What Are Protists? • “Dumping ground” kingdom • Eukaryotic • Heterotrophic and/or autotrophic • Single or multicellular • Ancestors to animals, plants, fungi
Animal-like Protists • Called Protozoans • Unicellular • Require water (live in water or moist soil) • Most heterotrophic • Some photosynthetic • Most are free-living • Some parasitic
All Life Functions in Just One Cell • Have food and waste VACUOLES for storing and digesting food & wastes • Many are capable of MOVEMENT • RESPOND to environment – some have light sensitive eyespot Amoeba Paramecium
All Life Functions in Just One Cell • Maintain HOMEOSTASIS • Contractile Vacuoles pump out excess water • Form Protective Cysts when food or water is scarce (dormant stage with hard covering) Contractile Vacuole Pumping
Plant-like Protists • Photosynthetic • No true roots, stems, leaves Golden Algae Red Algae
Plant-like Protists • Photosynthetic • No true roots, stems, leaves Golden Algae Green Algae Red Algae Brown Algae
Fungi-like Protists • Heterotrophic • Decomposers • No cell walls Slime Molds Water Molds
Reproduction • Reproduction • Asexual: fission • Sexual: produce gametes (specialized sex cells) • Advantage: new combinations of genes from both parents (Red Queen Hypothesis)
Reproduction • All reproduce ASEXUALLY • Binary Fission - divides into 2 identical individuals (clones) • Rapid reproductive rate
Some Reproduce SEXUALLY Conjugation - Opposite mating strains pair and exchange genetic material (DNA)
General Characteristics • Eukaryotic • Unicellular • Some may live in colonies • May be Autotrophic or Heterotrophic or Both • Some are motile • Appeared about 1.5 BYA
Classified into Three Main Groups • Animal-like… heterotrophs capable of locomotion • Plant-like… photosynthetic autotrophs • Fungus-like… decomposers that reproduce by spores • Some protists may exhibit both animal-like & plant-like characteristics
Sizes of Protists • Unicellular organisms • microscopic • Colonies • loosely connected groups of cells • Coenocytes • multinucleate masses of cytoplasm • Multicellular organisms • composed of many cells • can get very large – some brown algae (the giant kelps) can be 100 feet in length
Locomotion • Protozoa used to be classified according to how they move. • Ciliates use fine “hairs” called cilia • Flagellates use longer, whip-like hairs called flagella • Amoebas and their relatives use pseudopodia • Pseudopodia are also used to capture food • Sporozoans (apicomplexans) don’t have any ability to move (non-motile)
Importance • Importance of Protists • Heterotrophic protists = protozoa • Consume bacteria and other protists • Components of aquatic and soil food webs • help with recycling nutrients • Some cause disease • Malaria • Dysentery • Sleeping sickness • others
Interactions • Protists are free-living or symbiotic • Symbiotic relationships range from mutualism to parasitism
Classification of Selected Medically Important Protozoa • Four groups • Mastigophora - flagellates • Sarcodina - amoebae • Ciliophora - ciliates • Apicomplexa – aka Sporozoans • Based on: • Method of motility • Mode of reproduction • Stages in the lifecycle
Amoeba surround and engulf their food… the process is called phagocytosis.
Ciliophora • all use cilia for movement • have many specialized structures, including mouths, anal pores, contractile vacuoles, and two nuclei (a large macronucleus and small micronuclei) • Ex. – Paramecium and Stentor
Phylum Zoomastigophora • have flagella • some species of zooflagellates have mutualistic relationships • ex.- Trichonympha digests cellulose in the guts of termites
Others are parasites, like Trypanosoma, which causesAfrican Sleeping Sickness (coma).
Trypanosoma Red Blood Cells Trypanosoma White Blood Cell Tsetse Fly: carries Trypanosoma to humans; in other words, it’s a Vector
Phylum Sporozoa • are parasites • have no means of locomotion • form spores that are dispersed by one or more hosts • ex. Plasmodium, which causes malaria
Portions of the Life Cycle of Plasmodium vivax Plasmodium vivax It’s Vector: Anopheles Mosquito Red Blood Cells
Pathogenic Flagellates: Trypanosomes • Giardia lamblia • Trichomonas vaginalis • Genus Trypanosoma • T. brucei causes sleeping sickness • T. cruzi causes Chagas disease
Giardiasis • Fecal-oral route of infection • recreational water, water, fomites, contaminated uncooked food • Symptoms normally begin 1 to 2 weeks (average 7 days) after becoming infected. • Symptoms • Diarrhea • Gas or flatulence • Greasy stools that tend to float • Stomach or abdominal cramps • Upset stomach or nausea • May lead to weight loss and dehydration • Symptoms of giardiasis may last 2 to 6 weeks.
Trichomonas vaginalis A flagellate - causes Trichomoniasis, a sexually transmitted disease
Trichomoniasis • STD • Clinical Features: • Trichomonas vaginalis infection in women is frequently symptomatic. • Vaginitis with a purulent discharge is the prominent symptom, and can be accompanied by vulvar and cervical lesions, abdominal pain, dysuria and dyspareunia. • The incubation period is 5 to 28 days. • In men, the infection is frequently asymptomatic; occasionally, urethritis, epididymitis, and prostatitis can occur.