Mold is a simple fungus that feeds on food sources like bread. Tiny spores land on the surface and start growing when moisture and warmth are present. Rub a cotton swab of household dust across a piece of bread, add a few drops of water, and seal it in a plastic bag. Place it in a warm spot and check it every day — within a few days, fuzzy patches appear.

Fungi grow best in warm, moist conditions. Cold temperatures slow their feeding on dead matter nearly to a halt. Placing bread samples at different temperatures shows this clearly, since the warm sample grows fungi the fastest.

Yeast is a fungus that feeds on organic matter, breaking it down in a visible way. When you sprinkle dry yeast on a banana slice and seal it in a bag, the yeast consumes the sugars and releases carbon dioxide gas. A plain slice sealed in a separate bag stays as the control. Over three to four days, the yeast-covered slice breaks down noticeably faster.

Blue mold (Penicillium) and gray mold (Botrytis cinerea) are two common fungi that feed on harvested fruit like pears. Coating the surface with oil or a chemical dip may block fungal spores from reaching the organic material they need. In this experiment, forty red D'Anjou pears are divided into four treatment groups — chlorine solution dip, water dip (control), zinc oxide solution dip, and vegetable oil wipe. After fourteen days at room temperature, each pear is rated on a visual mold scale from 1 to 10, and the average ratings reveal which treatment protects pears best.