1
Q
Six eukaryotic supergroups
A
- Amebozoa
- Opisthokonta (together with Amebozoa forms the Unikonta)
- Archaeplastida
- Excavata
- SAR
- CCTH/Hacrobia
2
Q
Defining features of the Opisthokonts
A
- Flagellated stages move with flagella towards the back, rather than the front
- Proposed that ancestor had one flagellum arising from single centriole
3
Q
Which groups comprise the Holozoa of the Opisthokonts?
A
- Ichthyosporea
- Capsaspora
- Choanoflagellates
- Metazoa (animals)
4
Q
What are the Choanoflagellates?
A
- Closes relatives to animals (have very similar cells to sponges - called “choanocytes”)
- May have role in multicellularity
- Silicate lorica basket - flagellated with actin-based microvilli to create current that brings bacteria to it
- Called the “collared flagellates”
- Mostly marine, some freshwater
- Very common in plankton, but so small they tend to pass through plankton nets
5
Q
What are the Capsaspora?
A
- Opisthokonts, Holozoa
- Filose amoeboid cell
- Symbiotic - found in snails
- Independent lineage from choanoflagellates
6
Q
What are the Ichthyosporids?
A
- Opisthokonts, Holozoa
- Commensals or parasites, all in association with animals
- Trophic (=feeding) stages are multinucleated cells with many large vacuoles
- CHITIN cell wall present
- Propagate via (opisthokont) flagellated stages, walled spores, or lobose amoebae
- Important pathogens of fish
7
Q
What are the general characteristics of the fungi? What groups does the fungi comprise?
A
- Chitin cell wall and lack of flagella (ancestor likely lost)
- Comprises Holomycetes, Microsporidia, Ascomycetes
8
Q
Describe the Ascomycota
A
- Yeasts (budding)
- Medically relevant (Candida albicans)
- Economically relevant (Saccharomyces cerevisiae)
9
Q
Describe the Microsporidia
A
- Fungi
- Important pathogens of insects
- Role as human pathogens is increased as a consequence of AIDS epidemic and use of immunosuppressant drugs (most infections GI, but ocular, respiratory, or muscular infections can occur also)
10
Q
What are the Rozellids? What group are they a part of? What is unique about this group of fungi?
A
- Rozellids are part of Cryptomycota
- Found in freshwater, marine, and soil environments
- Cryptomycota redefine fungi through their LACK of a chitin cell wall and PRESENCE of a flagellum
11
Q
What are the nucleariids?
A
- Basal relative of fungi
- Filose amoebae (=shape)
- Discoid mitochondrial cristae, completely atypical for Opisthokonts
12
Q
What are the two defining features of the Amoebozoa?
A
- Tubulinea: United by possession of tubular pseudopodia (filose - fine, thin pseudopods; lobose - thick, wide pseudopods)
- Unidirectional (monoaxial) cytoplasmic streaming (movement of things in the cytoplasm) –> cytoplasm always moves forward
13
Q
Describe the Amoeba and Giant Amoeba species
A
- Can be very large
- Have single polygenomic nucleus - nuclei divide simultaneously = a “plasmodium”
- Plasmodium = acellular, multinucleate mass; often enclosed by a slime sheath; often brightly coloured
14
Q
Describe slime molds
A
- Amoebozoa
- Mycetozoans
- Produce spores, share habitats with fungi
- Not saprophytic like fungi, they are bacterial predators
- Pseudopodia of amoeboid stages are often filose
15
Q
What is a myxomycete?
A
- Plasmodial slime mold
16
Q
What are dictyostelids?
A
- Amoebozoa
- Cellular slime molds - model system for cellular differentiation in eukaryotes
- Trophic stages generally amoebae, seldom uniflagellate amoeboflagellates
- Never form plasmodium
- Evolution of multicellularity - spore and stalk (spores are released and divide; stalks won’t have progeny)
17
Q
Describe the Archaeplastids
A
- Invented photosynthesis
- Morphological characteristics: Descendants of ancestral host cell that took up cyanobacterial endosymbiont (primary endosymbiosis is key feature of archaeplastids)
- Molecular characteristics: Many endosymbiotic genes transferred from plastid to ancestral host lineage; process = endosymbiotic gene transfer (EGT) - when this is shared between hosts, most likely explanation is that it diverged prior to divergence of lineages
18
Q
What are the three groups of the Archaeplastids?
A
- Glaucophytes (cyanobacterial symbiont)
- Viridiplantae (green algae and land plants)
- Rhodoplantae (red algae)
19
Q
Describe the viridiplantae
A
- Chlorophytes (green algae)
- Streptophytes (land plants and some algae)
20
Q
What are micromonas?
A
- Archaeplastids, Viridiplantae
- Very simple; may be smallest eukaryote
- One flagellum; no scales
- Very common and successful despite small size
- Model green algae
21
Q
What are volvox?
A
- Archaeplastids, Viridiplantae
- Green algae (Chlorophyceae)
- Between 500 to several thousand individual cells in periphery of mucilaginous shell
- Cells toward front have larger eyespots; daughter colonies tend to develop closer to the back
- Model system for multicellularity in algae and plants
- Unicellular and multicellular stages
22
Q
Describe the Glaucophytes
A
- Small group, rare, only in fresh water
- Contain blue-green plastids often called cyanelles
- Info on Archaeplastid origin
- Photosynthetic
23
Q
What are the Rhodoplastids?
A
- Red algae
- Lack flagella and flagellar roots in all life history stages
- Red plastids
- Most forms multicellular (likely arose early in evolution)
24
Q
Describe the Cyanidiophytes
A
- Rhodoplastids
- Unicellular
- Thick proteinaceous cell walls
- Often one single cup-shaped plastid
- Inhabit extreme environments
- Colour like that of cyanobacteria (i.e., not red!)
25
Provide an example of red algae
- Bangiomorpha pubescens - oldest multicellular eukaryote fossil reported: 1200MYA
- May be oldest clearly eukaryote fossil
- Very similar to examples of moderm red algae (e.g., Bangia atropopurea)
- Definitely an Archaeplastid - Archaeplastid symbiosis happened very early in lineage
26
What are the Excavata and what is the excavate hypothesis?
- Eukaryotic supergroup with very diverse morphology
| - Possess a ventral feeding groove
27
What are the Euglenozoa?
- Excavates
- Some free-living (photosynthetic)
- Some pathogens (Leishmania; Trypanosoma)
28
What causes Nagana?
- Excavates
- Trypanosoma species transmitted by the Tsetse fly
- Cattle die from severe anemia
29
What causes African Sleeping Sickness?
- Excavates
- Trypanosoma brucei
- Transmitted by Tsetse fly
- Causes damage to vascular, immune, CNS, and inflammation of brain
- Livestock can be reservoirs
30
What is Naegleria fowleri?
- Excavates
- Amoeba, free-living in warm bodies of fresh water
- Enters body of swimmers through nose
- Infects neural tissue (brain and spinal cord)
- Primal Amoebic Meningoencephalitis
- Feed on neural tissue
31
What are the metamonads and what are their defining characteristics?
- Excavata
- Defined by conspicuous Golgi and cytoskeletal apparatus
- Hydrogenosomes, no mitochondria
- Flagella, but NO GROOVE (exception)
- Almost entirely parasitic/symbiotic
- Anaerobic/microaerophilic (Trichomonads and Hypermastigotes)
32
Describe Trichomonas vaginalis
- Excavate, Metamonad
- Common parasite
- Infects genital tract
- Generally benign, but can increase risk of HIV or cancer
33
Describe Hypermastigotes
- Excavate, metamonad
- Obligate symbionts of wood-eating cockroaches and termites
- Anaerobe
- Very large cells, 100-300um
- Many rows of flagella with basal bodies arranged perpendicularly to parabasals (unknown why)
34
What are the diplomonads?
- Excavates (metamonad)
- Small group
- Many species have two karyomastigonts (symmetry in middle of cell). Resmble "double" organisms
- Highly diverged
- Many parasitic (Giardia, Spironucleus - hold in head disease in fish)
35
Describe the supergroup CCTH
- Haptophytes, Cryptophytes are united with two previously unplaced groups, the Telonemids and Centrohelids
36
Describe the haptophytes
- Not large group in terms of number of species but very ecologically important
- Mostly marine, some freshwater
- 3rd major group of primary producers in ocean, after diatoms and dinoflagellates
- Produce DMS (cloud condensation molecule) and therefore are implicated in cloud formation and global weather patterns
- Generally flagellated forms, some species coccoid (often embedded in mucous, filamentous or colonial)
- Have calcium carbonate shells
- Blooms fix lots of carbon; lots of carbon in shells as well (acid will dissolve shells, releasing carbon into atmosphere)
37
Describe the cryptomonads
- Haptophyte
- Hard to find/study
- Very small and inconspicuous; delicate
- Usually free-living flagellates, but forms encapsulated in mucous also exist
- Most photosynthetic, a few are not
- Both freshwater and marine forms
- Common in cold water and high latitudes
- Tolerate low levels of light, therefore found in deep ocean
- Cryptomonas sp. is only in fresh water and lost photosynthetic ability (but not plastid)
38
Describe the Telonemids
- High diversity
- Small cells, non-photosynthetic
- TWO posterior flagella
39
Describe the centrohelid heliozoans
- Rounded body surrounded by stiff axopodia (phagocytic pseudopodia containing MTs)
- Axopodia supported by internally interlinked MTs arranged in hexagonal patterns
40
What composes the SAR supergroup?
- Stramenopiles, Alveolates, and Rhizaria
| - So large that there is no single uniting feature (even within groups)
41
What is the morphological feature of the Rhizaria?
- United by presence of filose or reticulate pseudopodia (not a strong characteristic)
- Otherwise, shows huge diversity of size and body type
42
What are the three major groups of Rhizaria?
- Cercozoa (endomyxa, filosa)
- Foraminifera
- Radiozoa
43
Describe the cercozoa
- Part of Rhizaria
- Diverse group with photosynthetic flagellates (Chlorarachniophytes), heterotrophic flagellates (Cercomonas) or organisms covered in shells (e.g., Euglypha - very large protective shell; predatory!)
44
Describe Foraminiferans
- Large group, part of Rhizaria
- Some of the largest protists are in group. Xenophytes up to 25cm! (although most others are 6-12um)
- Still unicellular - multinucleate (plasmodium)
- Mostly marine; some colonize freshwater and terrestrial habitats
- "Pave sea floor" because they are so abundant
- Skeletons classified according to material they are made of: glycoprotein (organic shells); sand grains glued together (glue is organic matrix, calcium carbonate, or both); calcium carbonate
- Make around 1/4 of global calcium carbonate
- Skeletons can have compartments
- Nummulites (sp.): Fossil forams, main component of rock used to make Egyptian pyramids
45
Describe the Radiozoa
- Always planktonic, always marine
- Exist at all depths, including deep sea
- General morphology of group reflects adaptation to planktonic lifestyle (very diverse morphology)
46
Describe the Stramenopiles
- Stramenopiles (straw hair) refers to typical tripartite mastigonemes (hair/extensions) of group
- Flagella with three hairs on end
- Mastigonemes reverse thrust of flagellum: beating anterior flagellum pulls cells forward
- Stramenopiles = heterokonts
- Heterokonts have two flagella that differ in unique way. One if long, forward-directed. Other is short, smooth, and generally directed towards back
- Place photosynthetics together; stramenochromes/sloomycetes
47
Describe the diatoms
- Stramenochromes
- Ubiquitous in marine and freshwater
- One of the largest protist groups
- Responsible for 20% of global primary production
- Have two parts: Diatom Frustule (cells encased in unique type of siliceous (=glass) wall that takes form of box with overlapping lid
- When nutrients are low, diatoms sink and create large sections of ocean floor covered in fossil siliceous remnants of diatom frustules - large carbon sink
48
Describe brown algae
- Stramenochromes
- Microscopic to large kelp forests
- No unicellular species
- Huge primary producers in coastal areas, especially temperate and polar regions
- Not directly related to red/green algae
49
What are sloomycetes?
- Oomycetes
- Plant pathogens
- Non-photosynthetic heterokonts
- Very similar to fungi (look like fungi and infects like fungi) = horizontal gene transfer!
- This facilitated evolution of plant parasitism
50
What are sloomycetes responsible for?
- Ireland potato blight
| - Phytophthora infestans (likes wet cool summers)
51
What are the alveolates? What is their defining feature? What are the three major groups?
- Alveolae are flattened vesicles that lie below the plasma membrane
- Very robust in phylogenetic trees
- Three groups: ciliates, dinoflagellates, apicomplexa
52
Describe the ciliates
- Alveolate
- Many small flagella-cilia
- Mainly aquatic
- Nuclei of two types: Micronucleus (diploid, transcriptionally inactive, germ-line); macronucleus (polygenomic, transcriptionally active, control phenotype)
- Ecology: harbour photosynthetic bacteria-algae symbionts; can be raptorial feeders (chase prey); some are filter feeders
- Transformations: can transform into raptorial feeders when starved due to changes in transcription
- Often live in guts of mammals as commensals, digest soluble carbohydrates or starch grains
53
Describe the dinoflagellates
- Alveolate
- Both photosynthetic and non-photosynthetic species
- All aquatic environments
- Defined by presence of TWO flagellum (one transversal flagellum; one longitudinal flagellum)
- Many also possess plates/scales
- Cause red tides = phytoplankton blooms
- Fix a lot of carbon
- Two ways dinoflagellate blooms can be harmful: Toxins may act on fish and kill them or may accumulate in organisms; high densities of non-toxic cells in water may cause harm by decreasing oxygen levels and killing other aquatic life
54
Describe the Apicomplexa
- Alveolates
- Almost entirely parasitic
- Have "apical complex" (special set of organelles used to penetrate host cells; part of apicoplast - used to be chloroplast, but lost photosynthetic ability)
- Possess remnant plastid, unusual golgi organization
- Causes diseases of agricultural and human importance
- Plasmodium - causes malaria (should target apicoplast to develop treatment)
BIOL 322
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