Protozoan Group Flashcards
What is a protozoan
Distinctly animal like: no cell wall
At least one motile stage in life cycle
Most ingest their food
Not a mono phyletic clade but share a basic body plan/grade
Completely contained within 1 plasma membrane (single celled)
What was first evidence of life on earth
First cells were prokaryotes
Unicellular eukaryotes appeared later, likely through serial endosymbiosis.
Mitochondria and plastids were likely small prokaryotes living within larger cells.
Where to find Protozoa
Everywhere!
All require moisture
Many free living but also numerous symbionts
Mutualistic, commensalism, parasitic
How do we classify Protozoa
Constantly under revision due to new molecular data so we will focus on Clades rather than taxonomic levels
Form and function of Protozoa
Single celled but special features of particular organelles can be defining features for Clades
Important organelles?
Nucleus: membrane bound structure containing genetic material as chromosomes. Nucleoli also often present.
Mitochondria: energy acquisition using oxygen. Also contains DNA (former prokaryote?)
Form of internal cristae can serve to group stuff into Clades.
More organelles?
Hydrogenosomes: substitutes when oxygen isn’t present.
Kinetoplasts: derivatives of mitochondria.
Golgi apparatus: part of secretory system. Parabasal bodies are structures with similiar function.
Plastids: organelles containing photosynthetic pigments, ex. Chloroplasts. Comes from ancestral engulfment of Cyanobacteria
Even more organelles?
Extrusomes: membrane bound organelles used to extrude something from a cell.
Important functions: locomotion?
Many protozoans capable of directly moving, chiefly by 2 means
Cilia and flagella: same ultra structure but different actions. Differ in beating patterns.
Flagella: undulating movement. Force generated in same dir as flagellum axis.
Cilia: like oars. Perpendicular strokes like oars on a row boat.
Micro tubules?
Both flagella and cilia have micro tubules. 9 pairs around central pair. 9+2 arrangement (axoneme) covered with continuous movement.
Different arrangements at entrance to cell. 9 triplets (kinetochore/basal body)
How do cilia and flagella propel protozoans
Sliding-micro tubule hypothesis
Pseudopodia?
Temporary protrusions of cytoplasm. Locomotion and ingestion in Protozoa and other ameboid cells. Aka leukocytes.
Exist in several forms.
Actin filaments assemble and disassemble to cause contractions and flowing of endoplasm by pressure.
Types of pseudopodia?
Lobo podia is most familiar.
Filipodia is thin extensions containing only ectoplasm.
Reticulopodia is repeatedly rejoin to form net like mesh.
Axopodia is supported axial rods of micro tubules.
Nutrition and digestion?
2 groups:
Autotrophs: synthesize own organic molecules.
Heterotrophs: must get organic molecules from others.
Heterotrophs either ingest visible food particles via phagocytosis (phagotrophs/holozoic feeders) or ingest in soluble form (osmotroph/saprozoic feeders)
Excretion?
Taken care by contractile vacuoles.
Usually in ectoplasm, act as pumps.
Reproduction?
Protozoans can reproduce sexually or asexually.
Asexual reproduction?
Cell multiplication producing genetically identical individuals via fission.
Binary fission is most common.
Sexual reproduction?
All protozoans reproduce asexually but there can still be genetic recombination.
Sexual process may exceed asexual processes but an embryo is never formed.
Protozoans sex?
Reduction in chromosome # (diploid to haploid)
Development of gametes/gametic nuclei (pronuclei).
Fusion of gametic nuclei (fertilization).
Meiosis reduces chromosome # before gametic formation (gametic meiosis).
Fusion–>diploid
Some do meiosis after fertilization. Haploid individuals then produced asexually via zygotic mitosis.
Syngamy?
Fertilization of 1 individual gamers by another. Not all protozoans produce gametes tho.
Autogamy?
Gametic nuclei result from gametic nuclei by meiosis and fuse to form a zygote within the same individual.
Conjugation?
Exchange of gametic nuclei occurs between paired organisms.
How do protozoans withstand extreme temperatures?
Ability to form cysts–>dormant form with resistant covering. Stops metabolism.
Encystment triggered by favourable conditions.
Class opisthokonta?
Mitochondrial cristae, 1 posterior flagellum, shared amino acid sequence.
Mostly metezoans and fungi.
Class called choloroflagellates.
Choanoflagellages?
Colonial Protozoa considered most likely sister taxa to the metezoans. Strong similarity between cells of choanocytes and sponges.
Class heterokonta?
Tubular mitochondrial cristae, 2 diff flagellum at anterior end.
Brown and yellow algae, diatoms, opalinids.
Clade viriplantae?
Chloroplasts,some have flagella
Green algae, bryophytes, green plants
Phylum chlorophyta?
Autotrophic. Single celled and colonial algae. Life cycle and development resembles that of metazoans.
Phylum euglenozoa?
Series of micro tubules beneath plasma membrane to stiffen pellicle. Divided into 2 subphyla: euglenids and kinetoplastids
Euglenids?
Chloroplasts with double membrane suggests secondary endosymbiosis.
Euglena is good representative. Can either use light (autotrophic) or become heterotrophic if not enough light is present. –>mixotrophs.
Kinetoplastids
Single large mitochondrion with DNA mass (kinetoplast).
Free living prokaryote consumers (aquatic or moist habitats)
Can also be parasites
Best known in genus trypanosoma.
Cause of sleeping sickness in Africa.
Phylum retortamonda
Lack mitochondria (retorting cuz it lacks) No longer considered a phylum but divided into 2 Clades: retortamonads+diplomonads
Retortamonads?
No mito and commensal+parasitic unicells.
Diplomonads
No mito but have 2 equal sized something and multiple flagella. Commensal and parasitic unicells too. Giardia is an example (looks like ghost)
Parabasalida?
Rod of micro tubules (axol body), absence of microchondria, Parabasal body
Mostly parasitic. Best known includes trichomonad Protists. Like trichomonas vaginalis (loooool). Can outcompete beneficial microbes and become infective.
Clade alveolata?
Membrane bound sacs (alveoli) just under PM
Divided into 3 phyla–>flagellate group (dinoflagellata), parasitic group (apicomplexa), group that move by cilia (ciliophora).
Phylum ciliophora?
All possess cilia at some state for feeding and/or movement. Arrangement varies. Diverse group of free living and symbiotic members.
Ex. Paramecium.
Cilia often short and often in longitudinal/diagonal rows. Cover entire surface or restricted. Can be fused into a sheet or into smaller membranelles. Both of these propel food into cytopharnyx. Fused cilia can form stiffened tufts (cirri) and aid in locomotion.
More on ciliophora?
Kinetosomes join fibrous structural system underneath the pellicle to form the infraciliature.
Some ciliates have small bodies embedded bw bases of cilia.
Toxicysts and trichocysts respond to mechanical stimulation and release thread like structure.
Most are holozoic (ingest solids or liquids)~food enters through cytosome (mouth).
Even more on ciliophora?
Contractile vacuoles aid in water balance. No osmoregularity system otherwise.
Multinucleate–>macro nuclei responsible for day to day functions.
Micro nuclei responsible for sexual reproduction.
Asexual-binary fission
Mitosis of micronucleus followed by division.
Reproduction of ciliophora?
Sexual conjugation: temporary union to exchange chromosomal material via micronuclei.
Meiosis of micronucleus followed by division into 2 pronuclei, 1 of which is exchanged to fuse with another pronucleus to restore diploid num.
always bw individuals of 2 diff mating types in any given variety.
Dinoflagella
Characteristic shape often reinforced by cellulose plates two flagella in perpendicular grooves.
Many are photo autotrophic.
Abundant components of marine and freshwater plankton.
More on Dinoflagella?
Blooms are episodes of explosive population growth.
Cause of red tides. Some produce deadly toxins.
Some are bio luminescent. ATP driven chemical reaction seen when dense masses agitated, mutualistic relationship wit corals.
Phylum Apicomplexa?
1 end-apical complex
contains organelles specialize for penetrating host cells and tissues.
Very intricate lifecycles (sexual and asexual stages) that often require two or more hosts for completion.
All are endoparasites and divided into 2 classes:
Coccidea and gregarinea.
Coccidea?
Affect vertebrates and in vertebrates. Eg. Plasmodium (malaria).
Consequences of apicomplexa?
Affects 300 million people (30 million deaths/yr)
Continually changes surface proteins.
Wears out immune system!
Sequencing plasmodium genome may help identify potential vaccine targets.
Toxoplasma?
Found in 25% of world pop.
Causes congenital defects, schizophrenia?
Gregarinea?
digestive tract and body cavity of invertebrates.
Amebas?
Poly phyletic taxon
Body form and ability to make a shell evolved independently
Now divided into several distinct Clades based on shapes of pseudopodia!
Nonactinopods amebas?
Can have lobopodia, Filopodia, rhizopodia.
Mostly harmless but some are endoparasites
Cause of amoebic dysentery. (Contaminated drinking water).
3rd cause of death in world (100 000 per year)
Actinopod amebas?
Have axopodia
Poly phyletic clade: foraminiferans, radiolarians
Foraminiferans?
Secrete complex multichambered shells of calcium carbonate
Slender pseudopodia extrude and form a protoplasmic net to catch prey
Mostly marine
Radiolarians?
Intricate siliceous skeletons
Poly phyletic group
Planktonic marine animals
Among oldest Protozoa
