Classify each of the organisms as herbivore, carnivore, or omnivore: Heron, grass, frog, grasshopper, dead algae, tadpole, water boatman, yellow perch. Why are they what they were classified as?

Grass and dead algae are not in any of those categories - the dead algae especially as it is dead! Grasshoppers are herbivores. Water boatmen, frogs, and herons come closest to being carnivores as they eat insects and other pond life (and in the case of herons they eat frogs, tadpoles and water boatmen...) and don't tend to eat vegetable matter. Tadpoles eat almost anything, as do yellow perch, and are therefore omnivores. Sounds like homework, but a rather peculiar list to be given. Grass and algae are in the Plant Kingdom, and aren't classifiable as -vores. (Exceptions being the 'insectivorous' plants like sundew and Venus flytrap.) Herbi- indicated plant material, carni- indicated meat of some sort, and omni- indicates everything (or anything); -vore indicates eating. Humans are naturally omnivores, and great pandas are 'designed' as carnivores, despite their mainly bamboo diet (they DO eat meat as well, but keep it rather quiet - bad for the image!)