Thompson studied medicine at the university in his native city of Edinburgh, where he was greatly influenced by Charles Thomson, who had recently returned from the Challenger Expedition. In 1884 he became professor of biology (subsequently natural history) at University College, Dundee. In 1917, when he became senior professor, Thompson published On Growth and Form, in which he developed the notion of evolutionary changes in animal form in terms of physical forces acting upon the individual during its lifetime, rather than as the sum total of modifications made over successive generations – the latter being the traditional credo postulated by Darwinists. In a later edition (1942), however, Thompson admitted the difficulty of explaining away the cumulative effect of physical and mental adaptations, which can scarcely be accounted for in the experience of one generation. In addition to such theoretical work, Thompson was much involved in oceanographic studies, as well as fisheries and fur-seal conservation in northern Europe. He was one of the British representatives on the International Council for the Exploration of the Sea, from its foundation in 1902. He was also interested in classical science, publishing works on the natural history of ancient writers, including an edition of Aristotle's Historia Animalium (1910; History of Animals) and accounts of Greek birds and fishes.