Light, Heat, Electricity, and Magnetism Light travels in a straight line until it strikes an object. Light can be reflected by a mirror, refracted by a lens, or absorbed by the object. Heat can be produced in many ways, such as burning, rubbing, or mixing one substance with another. Heat can move from one object to another by conduction. Electricity in circuits can produce light, heat, sound, and magnetic effects.
Electrical circuits require a complete loop through which an electrical current can pass.
Magnets attract and repel each other and certain kinds of other materials. The characteristics of organisms Organisms have basic needs. Organisms can survive only in environments in which their needs can be met. The world has many different environments, and distinct environments support the life of different types of organisms. Each plant or animal has different structures that serve different functions in growth, survival, and reproduction.