Emerald Planet

It ... points toward a carbon dioxide-rich atmosphere as an environmental 'barrier' to leafy plants, the barrier at plants' evolutionary gateway only been lifted after carbon dioxide levels dwindled. Interestingly, an analogous barrier has been proposed for the Cambrian explosion of marine invertebrate animals in the form of low atmospheric oxygen levels. In the case of marine animals, a step increase in the oxygen content of the atmosphere seems to have coincided with the geological 'sudden' evolution of complex multicellular animals. (p. 29)

Plants, and their fungal partners below ground, are evidently engaged in a conspiracy of silence as they gradually consume the rocks beneath our feet over the ages. Careful investigations have shown them to dissolve rocks five times faster than normal, irrespective of whether they are tropical rainforests in Hawaii or conifer forests in the Swiss Alps. (p. 33)

Comments: Evolution favors systems that can circulate faster for they generate higher rates of return. That is how organic systems replace nonorganic systems because organic systems circulate faster.

Some further reading

Davies, P. (2003) The Origin of Life, Penguin.

Knoll, A.H. and Caroll, S.B. (1999) Early animal evolution: Emerging views from comparative biology and geology. Science, 284, 2129-37.

Nick Lane: Oxygen: the molecule that made the world FOr a more technical briefing, read Halliwell, B and Guttridge, J.M.C. (1999) Free radicals in biology and medicine, Oxford University Press