Atoms are arranged into molecules then into macromolecules which make up

Atoms are arranged into molecules, then into macromolecules, which make up organelles, which work together to form cells.

Atoms are the smallest and important building blocks of ordinary matter. Atoms have the properties of a chemical element and they can combine together to form molecules, and macromolecules which in turn form organelles that functions together to form cells. All gas, liquid, solid, and plasma is made up of ionized or neutral atoms.

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.