Index fossils (also known as guide
fossils, indicator fossils or zone
fossils) are fossils used to define
and identify geologic periods (or
faunal stages).
The material or substance on which an enzyme acts upon is known as the substrate, they are nothing but reacting molecules and or substances that are able to ultimately be converted to product substances. By the aid of biological enzymes, that lower the energy of activation needed for a chemical reaction to proceed.
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Answer:
Convection only occurs in liquids and gases. For example: Air and ocean