Stimuli are anything that causes arousal or enables an object to respond or react.
There are many different kinds of stimuli for which is different for every organism, for example, water, light and carbon dioxide are three stimuli and materials needed for photosynthesis in plants to manifest.
In humans, we have nutrients or food, oxygen and water for us to survive. These are stimuli, eyes need light as a stimuli for it see and function. Nasal receptors needs smell as stimuli caused by molecular reactions of an object as a stimuli. And others.
A pure substance is any substance on its own. For example, sand is impure for containing lots of different substances. However, diamonds are mostly pure for only containing one type of substance.
Whether a substance is pure or not doesn't relate to a substance's molecular structure, but different molecules in a substance. Water by itself is only H2O, therefore it still pure.
Water is not an element but a compound for containing different elements, however it still pure.
Can someone please help me with just this one question?
Cells are the basic unit of structure in all living things. ... Since cells are in all living things, they provide information about all life. Because all cells come from other cells, scientists can study cells to learn about growth, reproduction, and all other functions that living things perform
