A stacking ring toy can represent an energy pyramid. A balloon can be blown up and let go to illustrate the jet propulsion locomotion of cephalopods. Then a strip of cellophane tape can be placed along the facing sides of the two balloons. If the balloons are further inflated, they will curve inward as guard cells do because of the fact that the tape prevents one side from expanding normally. A Y-tube will make will make it easier to fill the two balloons simultaneously.
Illustrate leaf veins with drinking straws.
Bundle 10 large diameter straws together with 10 small-diameter straws. The larger straws represent xylem while the smaller straws represent phloem. A piece of dryer vent tubing can be used to illustrate the spiral vessel structure of xylem. Spiral tubing from a carpet shampooer or shop vacuum could also be used. A three-prong adaptor simulates the way transfer RNA allows an amino acid to fit the messenger RNA molecule even though the shapes of the two molecules are not complementary.