Lesson 12 of 12 · 16 min
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Must-know facts
25 facts
- 01Aristotle: plants as trees, shrubs and herbs; animals with and without red blood.
- 02Linnaeus: two kingdoms, Plantae and Animalia.
- 03R.H. Whittaker (1969): five kingdoms Monera, Protista, Fungi, Plantae, Animalia.
- 04Whittaker's criteria: cell structure, body organisation, mode of nutrition, reproduction, phylogenetic relationships.
- 05Monera wall: non-cellulosic (polysaccharide + amino acid); Fungi wall: chitin; Plantae wall: cellulose; Animalia: no wall.
- 06Three-domain system splits Monera into two domains, giving six kingdoms.
- 07Bacterial shapes: coccus, bacillus, vibrium (comma), spirillum (spiral).
- 08Archaebacteria: halophiles, thermoacidophiles, methanogens; different wall structure; methanogens make biogas in ruminant gut.
- 09Nostoc and Anabaena fix nitrogen in heterocysts.
- 10Mycoplasma: no wall, smallest living cells, can live without oxygen.
- 11Diatoms: soap-box silica walls, diatomaceous earth, chief producers of the oceans.
- 12Gonyaulax causes red tides; dinoflagellates have cellulose plates and two flagella.
- 13Euglena: pellicle instead of wall, two flagella, pigments same as higher plants.
- 14Slime mould spores have true walls and are dispersed by air.
- 15Protozoan examples: Amoeba and Entamoeba (amoeboid), Trypanosoma (flagellated, sleeping sickness), Paramoecium (ciliated), Plasmodium (sporozoan, malaria).
- 16Fungal walls: chitin and polysaccharides; coenocytic hyphae have no septa.
- 17Sexual cycle of fungi: plasmogamy, karyogamy, meiosis; dikaryon (n + n) in ascomycetes and basidiomycetes.
- 18Phycomycetes: aseptate coenocytic mycelium, zygospore; Mucor, Rhizopus, Albugo.
- 19Ascomycetes: conidia exogenous, ascospores endogenous in asci; Penicillium, yeast, Aspergillus, Claviceps, Neurospora.
- 20Basidiomycetes: four exogenous basidiospores on the basidium; Agaricus, Ustilago, Puccinia.
- 21Deuteromycetes: only asexual stage known; Alternaria, Colletotrichum, Trichoderma.
- 22Partly heterotrophic plants: bladderwort, Venus fly trap (insectivorous), Cuscuta (parasite).
- 23Ivanowsky 1892, Beijerinck 1898 (Contagium vivum fluidum), Stanley 1935 (crystallised virus).
- 24A virus has RNA or DNA, never both; bacteriophages usually double-stranded DNA; plant viruses usually single-stranded RNA.
- 25Viroid: free low-molecular-weight RNA, no protein coat, potato spindle tuber, Diener 1971. Prions: misfolded protein, BSE and CJD. Lichen: phycobiont + mycobiont, pollution indicator.
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Key terms
24 terms
- Five kingdom classification
- Whittaker's 1969 system: Monera, Protista, Fungi, Plantae and Animalia.
- Three-domain system
- A proposed system that splits Monera into two domains and places all eukaryotes in a third, giving six kingdoms.
- Archaebacteria
- Bacteria of extreme habitats (halophiles, thermoacidophiles, methanogens) with a distinctive cell wall structure.
- Heterocyst
- A specialised cell in some cyanobacteria, such as Nostoc and Anabaena, where atmospheric nitrogen is fixed.
- Mycoplasma
- Wall-less prokaryotes; the smallest living cells known, able to survive without oxygen.
- Diatomaceous earth
- Gritty deposits of silica-rich diatom walls, used for polishing and for filtering oils and syrups.
- Red tide
- Reddening of the sea by rapid multiplication of red dinoflagellates such as Gonyaulax, whose toxins can kill fish.
- Pellicle
- The protein-rich flexible layer that euglenoids have in place of a cell wall.
- Plasmodium (slime mould)
- The spreading aggregation formed by a slime mould in favourable conditions.
- Pseudopodia
- Temporary projections ('false feet') used by amoeboid protozoans to move and capture prey.
- Hypha and mycelium
- A hypha is a single thread of a fungal body; the network of hyphae is the mycelium.
- Coenocytic hypha
- A hypha without cross walls, a continuous tube of cytoplasm with many nuclei.
- Plasmogamy
- Fusion of the protoplasms of two gametes or cells, the first step of the fungal sexual cycle.
- Karyogamy
- Fusion of two nuclei, the second step of the fungal sexual cycle.
- Dikaryon
- A cell with two separate haploid nuclei (n + n), found between plasmogamy and karyogamy in ascomycetes and basidiomycetes.
- Ascus and ascocarp
- The ascus is the sac in which ascospores form; ascocarps are the fruiting bodies that hold the asci.
- Basidium and basidiocarp
- The basidium bears four basidiospores on its outside; basidiocarps are the fruiting bodies that hold the basidia.
- Deuteromycetes
- The imperfect fungi, whose sexual stage is unknown; they reproduce only by conidia.
- Alternation of generations
- The alternation of a diploid sporophytic phase and a haploid gametophytic phase in plant life cycles.
- Capsid and capsomeres
- The capsid is the protein coat of a virus; capsomeres are the small subunits that build it.
- Bacteriophage
- A virus that infects bacteria, usually with double-stranded DNA.
- Viroid
- An infectious agent of free, low-molecular-weight RNA without a protein coat, e.g. the cause of potato spindle tuber disease.
- Prion
- An infectious agent made of abnormally folded protein that causes neurological diseases such as BSE and CJD.
- Phycobiont and mycobiont
- The algal (autotrophic) and fungal (heterotrophic) partners of a lichen.