Chapter 28 Protists 1 m Living Small Protist is the informal name of the kingdom of mostly unicellular eukaryotes Antoni van Leeuwenhoek was the first to discover them in a drop of pond water Since Protista constitutes a polyphyletic group it is no longer valid as a Kingdom currently eukaryotes are arranged into four supergroups Species Panthera pardus Hierarchical Classification Linnaeus introduced a system for grouping species in increasingly broad categories The taxonomic unit at any level of the hierarchy is called a taxon Genus Panthera Family Felidae Order Carnivora Class Mammalia Phylum Chordata Kingdom Animalia Bacteria Domain Eukarya Archaea Linking Classification and Phylogeny Systematists depict evolutionary relationships in a branching diagram called a phylogenetic tree Each branch point represents the divergence of two evolutionary lineages from a common ancestor Branch point where lineages diverge Taxon A 3 Taxon B 4 2 ANCESTRAL LINEAGE 1 Taxon C Taxon D 5 Taxon E Taxon F Taxon G This branch point represents the common ancestor of taxa A G Sister taxa This branch point forms a polytomy an unresolved pattern of divergence Basal taxon A taxon is equivalent to a clade only if it is monophyletic consisting of an ancestral species and all its descendants A B Group I C D E F G a Monophyletic group clade A paraphyletic grouping consists of an ancestral species and some but not all of the descendants A B C D E F G b Paraphyletic group Group II A polyphyletic grouping consists of various species that lack a common ancestor A B C D E F G c Polyphyletic group Group III Figure 28 2 Excavata Archaeplastida 5 m 20 m 50 m Parabasalids Euglenozoans Excavata Diplomonads Stramenopiles Diatoms Golden algae Brown algae Apicomplexans Ciliates SAR clade Alveolates Dinoflagellates SAR Clade 50 m Unikonta Forams Rhizarians Cercozoans Radiolarians Green algae Chlorophytes Charophytes Land plants Archaeplastida Red algae Tubulinids Entamoebas Nucleariids Opisthokonts Fungi Choanoflagellates Animals Unikonta Amoebozoans Slime molds 100 m 100 m Figure 28 2aa Parabasalids Euglenozoans Excavata Diplomonads Stramenopiles Diatoms Golden algae Brown algae Apicomplexans Ciliates Forams Rhizarians Cercozoans Radiolarians SAR clade Alveolates Dinoflagellates Excavates The clade Excavata is characterized by its cytoskeleton Some have an excavated groove on the side of the body Diplomonads Giardia Intestinalis 5 m Giardia intestinalis Some have modified mitochondria others have unique flagella Giardia intestinalis can infect people who drink contaminated water Brain eating Amoeba Heteroloboseids Naegleria fowleri Parabasalids have reduced mitochondria called hydrogenosomes that generate some energy anaerobically releasing hydrogen gas Flagella Trichomonas vaginalis Undulating membrane 5 m Parabasalid Trichomonas vaginalis a sexually transmitted parasite that can feed on the vaginal lining Pyruvate Acetate Euglenozoans the main feature distinguishing them as a clade is a spiral or crystalline rod of unknown function inside their flagella This clade includes the kinetoplastids and euglenids Flagella 0 2 m Crystalline rod Ring of microtubules Figure 28 2aa Parabasalids Euglenozoans Excavata Diplomonads Stramenopiles Diatoms Golden algae Brown algae Apicomplexans Ciliates Forams Rhizarians Cercozoans Radiolarians SAR clade Alveolates Dinoflagellates Kinetoplastids have a single large mitochondrion that contains an organized mass of DNA called a kinetoplast Includes species that feed on prokaryotes and others that parasitize plants animals and other protists Kinetoplast Contains multiple copies of mitochondrial DNA Mitochondrion Nucleus Flagellum Motility Golgi Kinetoplastids are responsible for several debilitating or even fatal diseases in humans African Sleeping Sickness Chagas Disease Leishmaniasis Trypanosoma Kinetoplastid that causes sleeping sickness 9 m Parasites have Multiple hosts Intermediate Host Definitive Host Organism in which a parasite reproduces sexually Organism in which a parasite does NOT reproduce sexually Reservoir Non human organism which can harbor parasites Disease control in any of these hosts Trypanosoma brucei life cycle Definitive Intermediate Tsetse fly Reservoir Blood Lymph Spinal Fluid Savannah Antelope Sleeping sickness related to Tse tse fly range 70 million at risk Stages of African Sleeping Sickness Early stages parasites in blood and lymph swollen lymph nodes and anemia Later stages parasite crosses the bloodbrain barrier confusion daytime sleepiness nighttime insomnia and finally coma CDC 1996 Winterbottom s sign Once the disease has crossed the bloodbrain barrier the treatment options are limited Late stage infection Chagas Disease Definitive Reduviid bug Intermediate Slow Growing Tissue Cysts Reservoir Bursting cells cause local inflammatory response Mice opossums armadillos Trypanosoma cruzi intracellular to white blood cells Reduviid Transmission 1 Infected reduviid bug takes blood meal Saliva not infected 2 Bug defecates during feeding Feces contain parasites 3 Host scratches bite wound Parasites enter host Reduviid feces Reduviid taking a blood meal Chagas Disease Acute 1 Most severe in children under 5 Swelling and redness at bite site Fever chills malaise Death can occur within weeks Chronic and asymptomatic 30 Organisms invade and multiply within host tissues including heart spleen liver and brain Chronic infections can last up to 20 years Chronic Chagas disease is a common cause for heart transplants Megacolon Chagas Disease Related to Reduviid Range At risk 100 million Humans infected 16 18 million Deaths 14 000 year Reduviid habitat Leishmaniasis Definitive Intermediate White BloodCell Infection Sandfly Reservoir Tissue specific Migration Rats dogs Leishmania major Leishmania donovani Leishmania braziliensis Disease range 350 million at risk 2 million cases year 60 000 deaths year Cutaneous Disease Leishmania major Dermal localization Self healing Can take months or years Leaves scarring Veils Secondary infection Cutaneous Leishmaniasis in Iraq Baghdad Boil arm leg Euglenids have one or two flagella that emerge from a pocket at one end of the cell Many are mixotrophs combine photosynthesis and heterotrophic nutrition Long flagellum Eyespot Short flagellum Contractile vacuole Light detector Nucleus Chloroplast Plasma membrane Euglena LM 5 m Pellicle Figure 28 2aa Parabasalids Euglenozoans Excavata Diplomonads Stramenopiles Diatoms Golden algae Brown algae