Diversity of Living Organisms: Classification, Plant Kingdom and Animal Kingdom
Diversity questions ask you to place an organism in the correct group from a list of diagnostic features, or to name the pigment, structure or symmetry that distinguishes one group from another. Learn the one or two unique features per taxon rather than long descriptions.
Classification and nomenclature
- Hierarchy: Kingdom, Phylum or Division, Class, Order, Family, Genus, Species.
- Binomial nomenclature uses genus and species; ICBN governs plants, ICZN animals; a type specimen anchors a name; taxonomic keys are dichotomous.
- Five kingdoms: Monera, Protista, Fungi, Plantae, Animalia; the three-domain system separates Bacteria, Archaea and Eukarya.
- Two-kingdom drawbacks: it does not separate prokaryotes from eukaryotes or autotrophs from heterotrophs.
Plant kingdom
- Chlorophyceae: chlorophyll a and b; Phaeophyceae: fucoxanthin; Rhodophyceae: phycoerythrin.
- Bryophytes are amphibians of the plant kingdom, with antheridia and archegonia and a dependent sporophyte.
- Pteridophytes are the first vascular plants, with a prothallus; Selaginella and Salvinia show heterospory.
- Gymnosperms bear naked seeds and generally lack double fertilisation.
- Angiosperms show flowers, double fertilisation and triple fusion.
Animal kingdom
- Porifera: choanocytes and spongocoel. Coelenterata: cnidoblasts. Ctenophora: comb plates. Platyhelminthes: flame cells. Aschelminthes: pseudocoelom.
- Annelida: metamerism and nephridia. Arthropoda: largest phylum, chitinous exoskeleton, Malpighian tubules. Mollusca: mantle and radula. Echinodermata: water vascular system and radial symmetry. Hemichordata and Chordata; chordates have a notochord, dorsal hollow nerve cord and pharyngeal gill slits.
Worked example
An animal shows radial symmetry, calcareous ossicles and a water vascular system. Radial symmetry with a water vascular system is the diagnostic combination for Echinodermata, for example a starfish; the water vascular system powers tube feet.
Traps that cost marks
- Do not apply double fertilisation to gymnosperms generally.
- Arthropoda, not Mollusca, is the largest phylum.
- Red algae use phycoerythrin; fucoxanthin belongs to brown algae.
- Lichens are symbiotic associations, not a taxonomic kingdom.