L2_BiologicalForms_BV106G_Protists (1).pdf

Biological forms and function The diversity of organisms - Protists Overview ‘Definition’ of protists and their position in the tree of life… Why are protists ‘interesting’? Main groups of protists and their characteristics… Protists (Protista) Consists (mainly) of one of the...

Biological forms and function The diversity of organisms - Protists Overview ‘Definition’ of protists and their position in the tree of life… Why are protists ‘interesting’? Main groups of protists and their characteristics… Protists (Protista) Consists (mainly) of one of the kingdoms in the old classical model of the tree of life (i.e. with 5 main groups = kingdoms) Is today, however, from an evolutionary perspective, considered to represent a ‘ragbag’ that contains many only distantly related kingdoms, i.e. it is a very heterogeneous group with a lot of variability and still partly unclear phylogenetic relationships within this groups. → protists: paraphyletic group with the only thing in common that they are eukaryotes, but not being animals, fungi or plants! Most simply defined as: those eukaryotes (= organisms with a cell nucleus) that remain after you have sorted out (i) fungi, (ii) land plants and (iii) animals … → protists ≈ simple, mostly single-cellular eukaryotes,! Consists of, among others: protozoa (Sw. urdjur) Many different kinds of ‘plankton’ But also different kinds of macro algae (multicellular) And some groups closely related to animals and fungi…. Protists: simple eukaryote organisms that are not land plants, animals or fungi!  Terminology flagellum (Sw. flagell): (lat. Flagellum = whip) is an extra-cellular tail-shaped (‘cellular organ’) that can be found in certain eukaryote and prokaryote cells. The flagellum looks like a whip and is usually used for movement. Amoebae-like: undefined, variable cell shape in some protists (not only true amoebas) with capacity to form protruding cellular extension (pseudopodia) to aid movement and uptake of nutrients. symbiotic: living in symbiosis with another organism (i.e. mutual co-existence where both parts benefit from the cooperation) parasitic: living off (inside or on) another organism (i.e. exploitation with negative effects on the exploited) autotrophic: ‘self-supporting’, i.e. an organism that produces its own energy rich compounds, often (but not always) by means of photosynthesis (photoautotroph) heterotrophic: organism that receives the energy rich carbon compounds it needs by consuming other organisms pathogen: organism that induces disease in another org. Why are protists ’interesting’? Many are representatives of very important ’functional groups’ in ecosystems, e.g. photosynthesizing plankton in the sea & lakes decomposers of dead organic material parasites and pathogens In addition, some groups of protists are believed to represent living remnants of ‘early stages’ (predecessors) of multicellular fungi, plants & animals and may therefor provide important insights into how the latter groups evolved in the first place… Main groups of eukaryotes & protists So called super-groups (in between domains & kingdoms): Excavata: diverse group of flagellates (Sw. Eukarya (domain) gisseldjur) – single-celled org. with whip-shaped ”tail” (organelle used for movement) Rhizaria: amoeba-like plankton organisms within a calcerous or silicon-based outer shell, e.g. Foraminifera and Radiolaria Chromalveolata: diverse group of important plankton organisms, such as golden algae, dinoflagellates (Sw. pansaralger), ciliates (Sw. flimmerdjur) & diatoms (Sw. kiselalger), and brown algae Archaeplastida: green algae, red algae, and charophyceans (Sw. charofyter) (and land plants), Unikonta Unikonta Amoebozoa: most ”true amoebas” and slime molds (Sw. slemsvampar) Note: Rhizaria + Chromalveolata Opisthokonta: choanoflagellates etc. (and animals sometimes grouped together as & fungi) ”SAR” clade! Kingdoms within Eukarya super- kingdoms groups ”SAR” clade Note: Rhizaria + Chromalveolata sometimes grouped together as ”SAR” clade! Groups of protists within Eukarya 1: super group Excavata ”SAR” clade Note: Rhizaria + Chromalveolata sometimes grouped together as ”SAR” clade! Excavata Group of both free-living and symbiotic single-celled protists, that also includes some important parasites of humans. Many lack ‘normal’ mitochondria (but usually have modified mitochondria). Diplomonads: group of flagellates (Sw. gisseldjur) with mitosomes (modified mitochondria) of which some are parasites (e.g. Giardia lamblia -> infections of intestines) Parabasilids: group of flagellates with hydrogenosomes (modified mitochondria) of which some are symbiotic (e.g. with cellulose decomposing bacteria in the gut of termites) and some parasites (e.g. Trichomonas vaginalis -> Trichomoniasis = genital infection) Euglenozoans: large and diverse group of flagellates that includes both free-living and parasitic forms (e.g. Trypanosoma → sleeping sickness, Chaga’s disease) Trypanosoma Genus of parasitic flagellates that among other things cause sleeping sickness (Trypanosoma brucei) and Chaga’s disease (Trypanosoma cruzi) Groups of protists within Eukarya 2: Chromalveolata ”SAR” clade Chromalveolata Large and diverse group that includes many important single-celled plankton organisms: dinoflagellates (Sw. pansaralger) diatoms (Sw. kiselalger) golden algae But also: Apicomplexa: large group of protozoa that are exclusively parasitic (causes e.g. malaria, cryptosporidiosis, toxoplasmosis) Ciliates (Sw. flimmerdjur) And: the multicellular Brown algae  dinoflagellates (Sw. pansaralger) Very large and variable group of single-celled plankton in mainly marine environments with an outer shell of ’tough plates’ (Sw. ”pansar-plåtar”) made of cellulose and with one or several flagella in ridges between the plates many are photosynthetic (photoautotrophic) and contribute to a large share of the primary production in the seas, other groups are mixotrophic, or heterotrophic Some species can send out light (bioluminescent) and cause e.g. ’milky seas’ / ’mareel’ / ’sea-fire’ (Sw. mareld) (Noctiluca scintillans), other species can cause ”red tide”… Some species produce toxins (dinotoxins) under certain conditions and can cause massive fish-kills and be dangerous to humans (e.g. ‘paralytic shellfish poisoning’) Some are endosymbiotic (e.g. the genus Symbiodinium), that is an important component of many reef building corals in the seas (but also sea anemones, jelly fish & sea slugs). They capture sunlight (photosynthesis) and contribute energy to its host (the cnidarian), which is responsible for the excretion of calcium carbonate. Symbiodinium in corals Diatoms (Sw. kiselalger) Large group of single-celled eukaryotes that comprise a very large proportion of the algae in both the sea and lakes. They contribute up to some 45% of the photosynthesis in the seas! Constitute important food for mussels, sea squirts and many fishes forms an outer shell of silica (silicon dioxide) composed of two parts (sometimes symmetrical). The shape of the shell is species specific and can be used for species identification. Some line up several cells in the form of chains or simple star- shaped colonies. Plankton spring bloom: part of the seasonal cycle of algal blooms in lakes and the seas: When conditions (mainly the supply of silicon) in the upper water layers are beneficial (usually in the spring) they can reproduce rapidly and become the dominating plankton for a short period. Environmental indicators: Since the shells are well-preserved in sediments they are frequently used to study the historical environment in and around lakes and marine areas Golden algae Large group of mainly photoautotrophic algae that mainly are found in freshwater systems (some species are mixotrophic). The name refers to their often golden brownish colour. Most are single-celled flagellates with one or two flagella Most are mobile and lack a shell, but some species (e.g. Dinobryon) have a shell or outer plates, live in colonies and are thus largely immobile. Apicomplexa: Large group of protists that are exclusively parasitic in a large variety of organisms, from segmented worms (annelids = Sw. ringmaskar), mollusks & arthropods (Sw. leddjur) to vertebrates (e.g. causing malaria, cryptosporidiosis, toxoplasmosis in humans) characteristics: an apical complex (apicomplex ≈ foremost/upper ‘device’, organelle used as a ’drill’ to enter the host cell some time during its life cycle). Lack of flagellum and pseudopodia (except for certain parts of the gamete stage) Most have a complex life cycle with alternating sexual and asexual reproduction Life cycle of Plasmodium Salivary gland of mosquito ’Tropical fever’ Ciliates (Sw. flimmerdjur/infusionsdjur) Free-living single-celled eukaryotes that can be found in all types of (but mainly nutrient rich) waters Can often very easily be obtained from and cultivated in ’hay infusions’ Characteristics: Large set of cilia (Sw. flimmerhår) all around the cell (including the mouth ridge) used for movement and transport of nutrients, and two differently sized nuclei Are for the most part heterotrophic (consumes bacteria, algae & other ciliates), but a few parasitic species exist (on fish) as well as mixotrophic species Brown algae Large group of multicellular algae that superficially resembles plants, but that are not closely related to either plants or animals. Many species of marine macrophytes belong to this group, e.g. bladder wrack & toothed/serrated wrack (Fucus vesiculosus and F. serratus, Sw. blåstång & sågtång), and many species of kelp) Are mainly found in near-shore areas affected by tide Many species are used for food (e.g. Laminaria in soups, mainly Japan) the photosynthetically active pigment phycoxantin is responsible for the characteristic green-brown color of these algae Life cycle of brown algae with alternating generations Alternating generations: the presence of multicellular haploid as well as diploid stages in the life cycle Groups of protists within Eukarya 3: Rhizaria ”SAR” clade Rhizaria Single-celled and amoeba-like eukaryotes that are heterotrophic (consumes and uses compounds metabolized by other organisms) Consists of among others: Foraminifers Radiolarians Foraminifers: small single-celled organisms in mainly marine environments that breathes nitrogen oxide instead of oxygen, and with a calcareous shell that often resembles that of tiny snails. Their empty shells form ‘calcareous ooze’ (Sw. kalkslam) that is a major part of some (but not all) sedimentary limestone (Sw. kalksten). They are important ‘index fossils’ (Sw. ledfossil) in sedimentary rocks from the Jurasic period and onwards Radiolarians: amoeba-like protozoans with a silicon based skeleton that live as plankton almost everywhere in the seas. Their shell form silicon ooze (Sw. kiselslam) and are important index fossils (Sw. ledfossil) in sedimentary rocks from the Cambrian period and onwards Groups of protists within Eukarya 4: Archaeplastida ”SAR” clade Archaeplastida Mostly multicellular, with the exception of some single-celled red- and green algae ‘Plants’ in a wide sense that consist of land plants and the, from an evolutionary point of view, closely related groups (kingdoms): Red algae (Rhodophytes) Green algae (Chlorophytes & Charophytes), and (land plants, Plantae) (the former two groups (red and green algae) can be assumed to shed light on important steps in the evolution of land plants) Green Red algae algae ? Red algae One of the oldest and largest groups of eukaryote algae Mainly multicellular and very abundant in warm marine environments (but can to a lesser extent also be found in colder/temperate environments) Have, in addition to chlorophyll, a pigment (phycoerythrin) that is responsible for the red color of the organisms and that enables photosynthesis in deeper water than other phototrophic organism groups Some species are used for food (e.g. nori in sushi) ‘Coral algae’ consists of a subgroup of red algae that excretes calcium carbonate and contributes to the build- up of coral reefs (NOTE: not the same as ‘coral animals’ or cnidarians that the main part of a coral reef consists of!)  Why are red algae red? The color of a ’plant’ is the color (wavelength of light) that dominates the fraction of light that is reflected (i.e. not absorbed by photosynthesis)!!! Blue-green light penetrates deeper into water -> Red algae pigment absorbes blue-green light Simplified picture of approximately how and reflects the little red deeply light of different colors (wavelengths) that remains! penetrates water and what proportion of the total amount of light remains Green algae Large group of both single-cellular, colonial & multicellular species in both marine, freshwater and terrestrial systems, that all are photoautotrophic. Consists of two main groups: Chlorophytes & Charophytes (Sw. Kransalger) Land plants are believed to have originated from a primitive ancestral green algae Charophytes (Sw. Kransalger) so closely resembles land plants (and may thus be very closely related to them) that they here are dealt with in the section of land plants Groups of protists within Eukarya 5: Unikonta - Amoebozoa ”SAR” clade  Unikonta - Amoebozoa Maybe a somewhat inconspicuous group, but the main group within protists that from an evolutionary point of view are believed to be most closely related to Opisthokonta (the group incl. animals & fungi) Organisms of amoeba-type (incl. ”true amoebas”) Contains both free-living and parasitic species Consists of three main groups: Slime molds (Sw. slemsvampar): fungi-like amoeba organisms that during a parts of their life cycle forms a large and mobile, often brightly colored plasmodium Gymnamoeba: single-celled amoebas that are common in the soil as well as in freshwater and marine systems, usually heterotrophic Entamoeba: parasitic amoebas that infect a large number of organisms (e.g. causes amoebic dysentery in humans) Life cycle of a slime mold Groups of protists within Eukarya 6: Opisthokonta ”SAR” clade Unikonta - Opisthokonta Finally at the last group of eukaryotes within Protista. Consists of animals & fungi (not protists!) and a few groups of single-celled protists, that, from an evolutionary point of view, are believed to be closely related to animals and plants All of these will therefor be dealt with during the lectures on animals and fungi…