It’s hard for children to understand evolution (how things change over time) and equilibrium (how things attain a steady and balanced state of being). During these early years, you can, however, talk about how things change over time and point them out to your child.
For instance, show your child a series of photos of himself from birth to the present and talk about the many ways he’s changed. And, you can talk about balance and the work it often takes to achieve it: Learning to ride a bicycle or walk with a book on his head are good examples.
Form and Function
One of the simplest themes in science is all around: The shape of a natural thing is almost always related to its function. Begin with man-made objects. Can your child guess the use of a thimble, a corkscrew, a phonograph record? When you are looking at animals, ask him questions such as: “What might those plates do on the stegosauros’s back?” “What sort of habitat would a web-footed platypus like?” His best guess will almost always be correct.