The "Viruses" interactive lesson introduces students to the hidden world of viruses—how they differ between plants, animals, and bacteria; how they enter cells and replicate; and how they can cause (or sometimes even prevent) disease. Activities for students • Identify plant, animal, and bacterial viruses using hints (drag & drop) • Explore the structure of the tobacco mosaic virus • Find all the ways plant viruses can enter through wounds or openings • Examine common symptoms of plant vira