Plants are referred to as autotrophs. Auto– means "self," and in this case, –troph means "feeding." Autotrophs are those organisms that make their own food. All plants are autotrophs, and so are algae and many bacteria. Organisms that are unable to produce glucose through photosynthesis are called heterotrophs. Heterotrophs obtain organic food molecules for energy and nutrition by eating other organisms or by eating and absorbing by-products of other organisms.