Scheme of Work Cambridge International as & a level

18.1.2 Describe the classification of organisms into three domains: Archaea, Bacteria and Eukarya.

18.1.3 State that Archaea and Bacteria are prokaryotes and that there are differences between them, limited to differences in membrane lipids, ribosomal RNA and composition of cell walls.

18.1.4 Describe the classification of organisms in the Eukarya domain into the taxonomic hierarchy of kingdom, phylum, class, order, family, genus and species.

18.1.5 Outline the characteristic features of the kingdoms Protoctista, Fungi, Plantae and Animalia.

18.1.6 Outline how viruses are classified, limited to the type of nucleic acid (RNA or DNA) and whether this is single stranded or double stranded.

Extend by prompting learners to use the taxonomic hierarchy of kingdom, phylum, class, order, family, genus and species to classify a variety of organisms. Explore the different types of species concept to deepen learners’ understanding.

Using internet research, learners prepare a poster explaining why the five-domain classification system was replaced by the three-domain system in the 1970s. Emphasise the evidence from molecular biology. Each poster must include a blank table with three columns (ready to accept examples of each of the three domains). After learners complete their work, discuss why viruses are not included in the three-domain classification. (I)

Learners identify examples of species that have been reclassified in the light of molecular evidence. This article describes the news that the African elephant, previously thought of as one species, Loxodonta africana, is in fact two: www.nationalgeographic.com/news/2010/12/101222-african-elephants-two-species-new-science/. You may wish to extend the discussion by considering the concept of convergent evolution, including the vertebrate and cephalopod eyes, e.g. www.zo.utexas.edu/courses/THOC/Convergence.html. Learners produce a factsheet for future reference. (I)

Learners summarise the characteristic features of the kingdoms Protoctista, Fungi, Plantae and Animalia. For example, they may produce a series of cards showing photomicrographs and photographs of various species with their characteristics on the reverse side. Further information and useful images: www.linnean.org/learning/teaching

Provide learners with a sheet listing all of the key terms and brief definitions. Ask them to link together 5–10 pairs of terms to write a set of summary notes on this topic. (F)

Recap the key terms associated with classification. For example, learners complete a crossword containing clues for various taxa, or identify the ‘odd one out’ in a series of words. For example, the odd one out in the series ‘vertebrate, mollusc and plant’ is the plant, because it is a kingdom. (F)