Apure substance that cannot be broken down into any other substance by chemical or physical means is a ?

A pure substance that cannot be broken down into any other substance chemical or physical means is a element.

Elements  are the elemnts have same numbers of protons or we can say that elements. It is made up of only one type of atom. example is hydrogen. In hydrogen one proton and one electron is present.

nucleus

would be most reasonable answer tbh

only about ten percent of the energy at one trophic level is passed on to organisms at the next trophic level. the remainder of the energy is used in life processes or lost as heat.