A change in the environment outside the organism that causes a change in the organism * 5 points
stimuls
internal stimulus
external stimulus
stable

lysosomes contain a variety of enzymes, enabling the cell to break down various biomolecules it engulfs, including peptides, nucleic acids, carbohydrates, and lipids (lysosomal lipase). the enzymes responsible for this hydrolysis require an acidic environment for optimal activity. hope i !

i'd say that the moon rock is about 2.2 billion years old.