In what organelle (cell component) does cellular respiration take place?

Cellular respiration takes place in mitochondria of a cell, hence it is also known as power house of cell , because it gives us energy in the form of ATP molecule .

the reason the two sea urchins don't compete with each other for food, resources, etc. is because the urchins have adapted to the environment but they have also adapted to each other. this is most likely because the genes of the sea urchins.

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds