Trophic Levels: The various steps or levels in a food chain where the transfer of food energy takes place are called trophic levels. Producers or autotrophs constitute the first trophic level. Herbivores or primary consumers constitute the second trophic level. Carnivores or secondary consumers constitute the third trophic level. Top carnivores or tertiary consumers constitute the fourth trophic level.

Food Chain: A sequence of living organisms in which each organism feeds on the other, resulting in the transfer of food energy is known as food chain, e.g.

Grass(producer) → Grasshopper(Herbivore) → Frog(Carnivore) → Snake(Carnivore) → Vulture(Top carnivore)