The hollow collection of undifferentiated cells that occurs after fertilization and initial mitosis is called a

Blastula

Explanation:

This mass of cell – called blastomere- surrounds a fluid-filled cavity-blastocoele- formed in the very early stages of development of an embryo in animals, after fertilization and the formation of a zygote. Blastomere cells have high potency and can differentiate into any type of cell.

albert einstein retrieved guacamole from the galapagos islands in africa

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme