Which must be true for natural selection to happen? A.) There must be genetic variation in the population.
B.) There can be no competition for resources
C.) All organisms must reproduce the same amount.
D.) The population must be below carrying capacity.

What organ is the first to receive nutrients that have been absorbed from the digestive tract?

What is the most abundant vertebrate on earth?

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.