Question

All animals-whether herbivores, carnivores or omnivores-depend on plants for their food. Discuss

Answer 1

plants are autotrophs. They prepare their own food using CO2,H2O, chlorophyll in the presence of sunlight. All the heterotrophs are unable to prepare their own food because they don't have chlorophyll.They depend upon autotrophs for food.

Answer 2

All animals in herbivores depend on plants for their food because plants are the only organisms in this earth that can synthesize its own food by means of photosynthesis reaction. The herbivores are the only animals that entirely depend on plant.

Hence, an herbivore eats a plant to get energy, this energy is in turn transferred to a carnivore when it feed on an herbivore. Omnivores in turn feed on all plants, herbivore and carnivore for their energy, so ultimately the source of energy becomes a plant.  

Thus, all the animals which includes herbivores, carnivores or omnivores depend on plants in one way or another.