This topic follows the development of multicellular organisms from single cells to complex individuals. Cell structure and ultrastructure, cell division, the importance of fertilisation, the roles of stem cells, gene expression, cell differentiation and tissue organisation are all considered within this topic, as is the role of the genotype, epigenetics and the effect of environment on phenotype.
Students should be encouraged to carry out a range of practical experiments related to this topic in order to develop their practical skills. In addition to the core practicals detailed below possible experiments include examination of animal cells under the microscope and using electron micrographs, plant tissue culture to demonstrate the totipotency of plant cells, and demonstration of how a gene can be switched on by, for example, the induction of β-galactosidase.
Opportunities for developing mathematical skills within this topic include using ratios, fractions and percentages, making order of magnitude calculations using decimal and standard form and using the appropriate number of significant figures, understanding the terms mean, median and mode, constructing and interpreting frequency tables and diagrams, bar charts and histograms, and completing a statistical test.