... kinds of organisms, from the plants, ani-mals, fungi, and algae that can be readily seen in nature, to the multitude of tiny creatures known as protozoa, bacte-ria, and archaea that can be seen ... potentially harmful materials are produced in plants, animals, and humans in the process of living. Plants release waste gases into the air through their stomata. Animals and humans sweep waste ... ChArACteristiCs of living things 18 A Closer look At living things RegenerationThe process by which plants and animals replace lost or damaged parts by growing them anew is called regeneration....