Chemical ecology

Cells that live in the soil have both a changing pattern of distribution and a changing pattern of chemical substances surrounding them. Sometimes the cells will be relatively independent of each other, and sometimes they will be closely linked in some type of colony or even a small multicellular organism. In considering the primitive organization of the soil and the role played by the chemical substances, I want to show that this chemical ecology gives a direct insight into the evolutionary origin of multicellularity and its development in the life cycle of an organism. The reason for choosing the organisms of the soil rather than aquatic forms is simply that the soil has more structure and more pattern; the environment of water is relatively homogeneous and constant, at least from the point of view of a microorganism. The size of the grains of soil, the air cavities, the moisture content, the distribution of organic, edible material will differ from one region to the next, or even in the same region over a period of time. The soil is a truly heterogeneous environment, and the problems of adapting to such conditions are correspondingly diverse.