Biomineralisation in the context of geological time

ABSTRACTThe basic properties of living systems are remarkably consistent and involve energy interactions between intracellular and extracellular environments. These interactions predispose living systems to deposit minerals from many solutions. The evolution of biomineralisation was not a single cellular invention but rather the association and perfection of a few of these fundamental properties of cell biology. The components of biomineralisation systems involve some mechanism for modifying the activity of at least one ion, an interface for initiating and possibly controlling crystal growth, a diffusion limited size and a mechanism for manipulating the growth of the crystal lattice. The evolution of these components of biomineralisation in the context of geological time inevitably concentrates on the Precambrian–Cambrian boundary. Over a time scale of less than 50 × 106 years there was a proliferation of metazoan phyla, the mineralisation in a large number of taxa and the exploitation of a diverse set of processes involving agglutinated sediments, silica, phosphates and carbonates. A large number of theories have been proposed to explain why biomineralisation occurred at this particular time. Such theories should recognise the importance of the incorporation of the citric acid cycle into the cellular metabolism of many organisms and its exploitation in an aerobic environment, the development of multicellularity which enormously increased the opportunities for modifying ion activities in diffusion-limited sites, and the exploitation of browsing and carnivorous feeding habits. These influences had major effects on ecosystems and population structures and put considerable selective pressure on the advantages that could be gained from a skeleton.