Trophic levels are the way ecology uses to organize the organisms that make up a food chain, where mass and energy transfer occurs between individuals or populations. The components of these chains can be simplistically divided into three broad groups: producers, consumers and decomposers. Foods that are involved in trophic levels have as their main elements carbon, hydrogen, nitrogen and oxygen. These elements are present at all trophic levels and are responsible for helping energy move from one trophic level to another.
Phylum. The classification system goes: Kingdom, Phylum, Class, Order, Family, Genus, Species. Anything that shares a class also share anything above it.
Release of a neurotransmitter across the synapse is triggered by the entry of Ca++ into the presynaptic axon. No Ca++ entry means no transmission across the synapse.
