Curiosity goes back to the dawn of human existence (EXIST). This irrepressible desire to know is not a ___________________________(1) (CHARACTER) of inanimate objects. Nor does it seem to be attributable to some forms of living organism which, for that very reason, we can scarcely bring ourselves to consider alive. A tree, for example, does not display ___________________________(2) (RECOGNISE) curiosity, nor does a sponge or even an oyster. If chance events bring them poison, predators or parasites, they die as ___________________________(3) (CEREMONIOUS) as they lived.

Early in the scheme of life, ___________________________(4) (DEPEND) motion was developed by some organisms. It meant an ___________________________(5) (ORDINARY) advance in their control of the environment. A moving organism no longer waited in stolid ___________________________(6) (RIGID) for food to come its way, but went out after it. The individual that hesitated in the ___________________________(7) (ZEAL) search for food, or that was overly ___________________________(8) (CONSERVE) in its investigation, starved.

As organisms grew more complex, more messages of greater variety were received from and about the ___________________________(9) (ROUND) environment. At the same time, the nervous system, the living instrument that interprets and stores the data collected by the sense organs, became ___________________________(10) (INCREASE) complex.