A Survey of Eukaryotic Cells and Microorganisms Part 8

Protozoan Identification 1 Unique appearance of most protozoa allows easy identification to the level of genus and often species by microscopic morphology alone Identification clues include: • Shape and size of the cell • Type, number, and distribution of locomotor structures • Presence of special organelles or cysts • Number of nuclei 74 Protozoan Identification 2 Medical specimens taken from human fluids, feces or vagina smeared directly onto a slide and observed with or without special stains Some cultivated on artificial media or in laboratory animals for further identification or study 75 Important Protozoan Pathogens 1 Pathogenic flagellates: Trypanosomes • Genus Trypanosoma • T. brucei – African sleeping sickness • T. cruzi – Chagas disease Long, crescent-shaped cells with a single flagellum Occur in the blood during infection Transmitted by blood-sucking vectors 76 Important Protozoan Pathogens 3 Infective amoebas: Entamoeba • Entamoeba histolytica – amebic dysentery Ingested cysts germinate in the small intestine Trophozoites migrate to the large intestine and grow They can invade the liver, lungs, and skin Common symptoms include gastrointestinal disturbances 77 Important Protozoan Pathogens 4 78 Concept Check: (7) Which of the following descriptions is true of both Algae and Protozoa? A. They are both photosynthetic B. They are both always unicellular C. They both contain mitochondria D. They are both heterotrophs 79 Concept Check: (8) Which of the following descriptions is true of both Algae and Protozoa? A. They are both photosynthetic B. They are both always unicellular C. They both contain mitochondria D. They are both heterotrophs Answer: C 80 Parasitic Helminths Multicellular animals, organs for reproduction, digestion, movement, protection Parasitize host tissues Have mouthparts for attachment to or digestion of host tissues Most have well-developed sex organs that produce eggs and sperm Fertilized eggs go through larval period in or out of host body 81 Major Groups of Parasitic Helminths Flatworms – flat, no definite body cavity; digestive tract a blind pouch; simple excretory and nervous systems • Cestodes (tapeworms) • Trematodes or flukes, are flattened, nonsegmented worms with sucking mouthparts Roundworms (nematodes) – round, a complete digestive tract, a protective surface cuticle, spines and hooks on mouth; excretory and nervous systems poorly developed 82 Helminth Classification and Identification 1 Classify according to shape, size, organ development, presence of hooks, suckers, or other special structures, mode of reproduction, hosts, and appearance of eggs and larvae Identify by microscopic detection of worm, larvae, or eggs 83 Distribution and Importance of Parasitic Worms Approximately 50 species parasitize humans Distributed worldwide; some restricted to certain geographic regions with higher incidence in tropics Acquired through ingestion of larvae or eggs in food; from soil or water; some are carried by insect vectors Afflict billions of humans 84 Concept Check: (9) Parasitic helminths reproduce by: A. Cysts B. Spores C. Eggs and sperm D. All of the above 85 Concept Check: (10) Parasitic helminths reproduce by: A. Cysts B. Spores C. Eggs and sperm D. All of the above Answer: C 86