puhekieltä A surface on which an organism grows, or to which an organism or an item is attached.
The rock surface of a rockpool is the substrate for a sessile organism such as a limpet.
2006, Edward A. Wasserman, Thomas R. Zentall, Comparative Cognition: Experimental Explorations of Animal Intelligence (ISBN 0195167651), page 520:
Detach/subtract tasks involve Severing a fixed attachment between environmental objects (or the substrate) or removing object(s) from another unattached object, so the latter is a more useful tool.
2000, Mike Hansell, Bird Nests and Construction Behaviour (ISBN 1139429086), page 90:
This definition of "tool" is not simple, but contains several elements. The tool must not be part of the animal's body (a beak is not a tool); the user must manipulate the tool in some way for it to realise its function; and, finally, a tool cannot be attached to the substrate. This is a fairly clear definition, but does seem to produce some rather arbitrary distinctions (Hansell 1987b). The spider Dinopis, for example, makes a small web which it holds in its legs, thrusting it down on passing ants. This is a tool, but all other webs, however complex, are not since they are anchored to the substrate. The woodpecker finch ... that uses a fine stick held in the beak to extract insect prey from wood, is a tool user, but a shrike ... that impales an insect on a thorn still attached to the bush is not.