Speed does not break down atoms in itself, but high speed collisions do, and that happens at very high temperatures, because temperature is random motion on a sub-microscopic scale.
Fungis. Any decomposer
First of all, it is scientifically impossible for any type of matter to reach light speed. Secondly, if said matter is near light speed, then that matter will increase in density as it increases in speed. Also, time will slow down around the matter as it increases in speed.
The mouth breaks down and absorbs sugars in the food we eat.
erosion
erosion
No. Chemical changes can only result in rearranging representative particles (atoms, molecules, formula units.) They can't break down atoms any farther than, well, atoms.
Any rock that breaks down into sediments and then pressed back into a solid form.
Bacteria that break down dead organisms are considered consumers. They are not the only consumers; any organism that feeds on another is a consumer.
You think to atoms of chemical elements.
Biodegradable
An atom is the smallest particle there can be and can't be broken down any further while compounds are composed of two or more different atoms of elements.
Any kind of decomposer will break down the tissue that made the lion. Bacteria, worms, small animals or even birds and larger animals.