In sexually reproducing animals, once fertilization of the egg takes place, the exists as a single cell until cell division begins.

Animal bodies (and even plant bodies for that matter) are complex enough that life couldn't exist without enzymes. enzymes are usually large, complex biological catalysts that are expensive to make. enzymes speed up the rate of chemical reactions without being used up during the reaction (they can be reused many times). they are highly specific in the reactions they regulate. knowing what enzymes are and how they function, why does this explain why complex life forms could not exist if there were no enzymes.

How can you approximate the number of calories required to keep you in energy balance?

Ais a group of individuals of the same that exist together in the same place at the same time