Taxonomy of Eukaryotes Flashcards
Endosymbiosis Theories
- Eukaryotes began as a nucleus-bearing lineage that later acquired mitochondria & chloroplasts by endosymbiosis
- Intracellular association between a H2-producing bacteria gave rise to mitochondria & an H2-consuming archaeal host. Nucleus was later developed
Amitochondriate eukaryotes
Eukaryotes that lack a mitochondrion
Mitosomes
- Reduced form of mitochondrion (no TCA or ETC)
- Involved in the maturation of iron-sulfurclusters
Hydrogenosome
- Present in eukaryotes whose metabolism is strictly fermentative
- carries out the oxidation of pyruvate to H2 , CO2 and acetate
Cysts: Functions
Protect the cells against deleterious environmental conditions
Major clades of Eukaryia
6 major clades:
* Archaeplastida
* Rhizaria
* Chromalveolata
* Excavata
* Amoebozoa
* Opisthokonta
Are eukaryia phylogenetically closer to bacteria or archaea?
Archaea
Archaeplastida: Species
- Red Algae (rhodophytes)
- Green Algae (chlorophytes)
Rhodophytes: Characteristics
- Mostly marine, some freshwater/terrestrial
- Red color is from phycoerythrin
- Mostly multicellular
Chlorophytes: Characteristics
- Mostly freshwater, some marine/terrestrial
- Unicellular (flagellated) or multicellular
- Sexual & asexual reproduction
Excavata: General characteristics
- Unicellular
- Flagellated
- Lacks chloroplasts
- Live in anoxic habitats
Excavata: Species
- Diplomonads
- Parabasalids
- Kinetoplastids
- Euglenids
Diplomonads
- Have 2 nuclei of equal size
- Have mitosomes
- Ex: Giardia (cause giardiasis)
Parabasalids
- Contain a parabasal body
- Have hydrogenosomes
- Ex: Trichomonas (STD in humans)
Euglenoids
Characterised by? Species?
- unicellular flagellated eukaryotes
- Kinetoplastids & Euglenids
Kinetoplastids
- Characterised by presence of kinetoplast
- Ex: Trypanosoma
Trypanosoma brucei (Kinetoplastid)
Disease? Environment? Transmission?
- Causes African sleeping sickness
- Lives and grows in the bloodstream
- Transmitted by the tsetse fly.
Kinetoplasts
A mass of DNA present in
their single, large mitochondrion
Euglenids
- Nonpathogenic & phototrophic.
- Contain chloroplasts, can exist as heterotrophs; will lose its chloroplast if incubated in the dark for a long time.
- Can feed on bacteria by phagocytosis
Chromalveolata: Species
Alveolata:
* Ciliates
* Dinoflagellates
* Apicomplexans
Stramenophiles:
* Oomycetes
* Golden algae
* Diatoms
What are alveolates characterised by?
Characterized by the presence of alveoli (sacs underneath the cytoplasmic membrane) which help cells maintain osmotic balance
* In Paramecium: alveoli = contractile vacuole
Ciliates
- Cilia for motility and food
- 2 nuclei (macronucleus & micronucleus)
Dinoflagellates
2 (transverse & longitudinal) flagella with different insertion points on the cell
Apicomplexans
- Obligate parasites of animals
- Contain apicoplasts
- Ex: Plasmodium (malaria)
Apicoplats
Degenerate chloroplasts that lack pigments & phototrophic capacity, but still carry many anabolic pathways
Stramenophiles: General characteristics
All have flagella with many short hairlike extensions
Oomycetes (water molds)
- Filamentous growth & the presence of coenocytic hyphae
- Cell walls are made of cellulose
Golden algae (chrysophytes)
Chloroplasts are dominated by fucoxanthin which gives it its golden-brown colour
Diatoms
Characteriste by frustules (cell walls made of silica)
Frustules
Diatoms
Cell walls made of silica with proteins & polysaccharides attached to it
Rhizaria
Distinguished by their threadlike pseudopodia
Foraminifera
Form shell-like structures called tests made from OM reinforced with calcium carbonate
Radiolarians
- Tests are made of silica
- Name derived from radial symmetry of tests
Amoebozoa
Use pseudopodia for movement & feeding
Gymnamoebas
- Unicellular
- Free-living in soil & aquatic environments
Entamoebas
- Unicellular
- Parasites of vertebrates and invertebrates
Slime Mold: Types
- Plasmodial slime molds
- Cellular slime molds
Plasmodial slime molds
- Masses of protoplasm of indefinite size & shape that contain multiple nuclei (vegetative form)
- Sporangium forms containing haploid spores
- Spores germinate, yielding a swarmer cell
- Fusion of 2 swarmer cells regenerates the diploid plasmodium
Cellular slime molds
Life cycle?
- Single amoebae (haploid) (vegetative form)
- Aggregate as a pseudoplasmodium
- Fruiting body is formed, cells differentiate into spores
- Form diploid macrocysts
- Macrocysts undergo meiosis to form new amoebae (haploid)
Opisthokonta: Fungi
- Most fungi are multicellular
- Cell walls are made of chitin
- Extracellular digestion
Coenocytic
Cytoplasm and nuclei are not subdivided into cells (multinucleated)
Septate
Nuclei are separated by cross wall
Ectomycorrhizae
Form a sheath around the plant root but does not penetrate it
Endomycorrhizae
The fungal hyphae is embedded in the plant root
Haustoria
Specialized fungal hyphae that penetrate plant cells & consume the cytoplasm
Mycoses
Human diseases caused by a fungus
Fungi: Reproduction
Asexual (most common):
* Growth and spread of hyphal filaments
* Asexual production of spores called conidia
* Simple cell division (budding)
Sexual:
* Fusion of 2 haploid cells to form diploid cell
* Diploid cell undergos meiosis to produce haploid spores
* Spores are resistant to drying, heating, freezing, chemicals
