Infer why chloroplasts are found mostly in the leaves of plants

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.

In which situations is the principle of cross-cutting relationship useful in determining relative age?

The activity of the modern sample is 1.10 bq . how long does that measurement take?