AIEM — ICSE Exam Prep

Biological Classification - Quick Revision

Aristotle: earliest scientific basis (morphology) - plants as trees/shrubs/herbs; animals by red blood or not.
Linnaeus: Two Kingdom system - Plantae and Animalia. Could not separate prokaryotes/eukaryotes, unicellular/multicellular, photosynthetic/non-photosynthetic.
Whittaker (1969): Five Kingdom Classification - Monera, Protista, Fungi, Plantae, Animalia. Criteria: cell structure, body organisation, mode of nutrition, reproduction, phylogenetic relationships.
Three-domain system splits Monera into two domains (six kingdom classification).

Monera: prokaryotic; noncellulosic wall; cellular body; autotrophic (chemosynthetic/photosynthetic) + heterotrophic.
Protista: eukaryotic; cellular; autotrophic (photosynthetic) + heterotrophic.
Fungi: eukaryotic; chitin wall; multicellular/loose tissue; heterotrophic (saprophytic/parasitic).
Plantae: eukaryotic; cellulose wall; tissue/organ; autotrophic (photosynthetic).
Animalia: eukaryotic; NO cell wall; tissue/organ/organ system; heterotrophic (holozoic etc.).

Bacteria are sole members; most abundant; live everywhere incl. extreme habitats. Shapes: Coccus (spherical), Bacillus (rod), Vibrium (comma), Spirillum (spiral).
Archaebacteria: harsh habitats - halophiles (salty), thermoacidophiles (hot springs), methanogens (marshy/ruminant gut, make biogas). Different cell wall structure.
Eubacteria: rigid wall; cyanobacteria = photosynthetic autotrophs with chlorophyll a, fix N2 in heterocysts (Nostoc, Anabaena). Chemosynthetic autotrophs oxidise nitrates/ammonia. Heterotrophic bacteria = decomposers; some pathogens (cholera, typhoid, tetanus, citrus canker).
Reproduce mainly by fission; spores in bad conditions; primitive DNA transfer.
Mycoplasma: smallest living cells, NO cell wall, survive without oxygen, pathogenic.

Chrysophytes (diatoms, golden algae): silica walls (diatomaceous earth), chief ocean producers.
Dinoflagellates: marine, photosynthetic, cellulose plates, two flagella; red tides (Gonyaulax).
Euglenoids: pellicle (no wall), two flagella; photosynthetic in light, heterotroph in dark (Euglena).
Slime moulds: saprophytic; form plasmodium; spores with true walls, air-dispersed.
Protozoans: all heterotrophs - amoeboid (pseudopodia, Entamoeba), flagellated (Trypanosoma, sleeping sickness), ciliated (gullet, Paramoecium), sporozoans (Plasmodium, malaria).

Heterotrophic; mostly filamentous (yeast unicellular); body = hyphae -> mycelium; coenocytic (multinucleate, no septa) or septate. Wall = chitin + polysaccharides.
Nutrition: saprophytes (dead matter), parasites (living), symbionts (lichens with algae, mycorrhiza with roots).
Sexual cycle: plasmogamy -> karyogamy -> meiosis; dikaryon (n+n) in ascomycetes/basidiomycetes.
Classes: Phycomycetes (aseptate/coenocytic; zoospores/aplanospores; zygospore; Mucor, Rhizopus, Albugo), Ascomycetes (sac-fungi; conidia + ascospores in asci/ascocarps; Penicillium, Aspergillus, yeast, Neurospora), Basidiomycetes (mushrooms/rusts/smuts; basidiospores on basidium/basidiocarp; Agaricus, Ustilago, Puccinia), Deuteromycetes (imperfect fungi; only conidia known; Alternaria, Trichoderma).

Plantae: eukaryotic chlorophyll-containing; cellulose wall; alternation of generations (sporophyte/gametophyte); includes algae, bryophytes, pteridophytes, gymnosperms, angiosperms.
Animalia: heterotrophic, multicellular, no cell wall; holozoic nutrition; store glycogen/fat.

Viruses: non-cellular, inert crystalline outside host; nucleoprotein with either RNA or DNA (never both); protein coat = capsid (capsomeres); obligate parasites; plant viruses ssRNA, bacteriophages dsDNA. Diseases: mumps, smallpox, herpes, influenza, AIDS.
Viroids (Diener 1971): free low-MW RNA, no protein coat; potato spindle tuber disease.
Prions: abnormally folded protein; BSE (mad cow), CJD.
Lichens: algae (phycobiont, autotroph) + fungi (mycobiont, heterotroph); good pollution indicators.