The organic matter in humus is made
a. dead worm
b. stem
c. roots
d. all of the above

Awic dietitian is meeting with a client who has an infant and a young child. the mother says that the young child is a very picky eater and will only eat crackers and juice. the health worker notices that the child's hair is brittle, his nails tear easily, and the skin inside his lower eyelids is very pale. these are all signs of iron deficiency.

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

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.