Specialized cells regulate the expression of genes because they
a. do not want the genes to become worn out.
b. cannot control the translation of proteins.
c. do not carry the complete genetic code in their nuclei.
d. do not need the proteins that are specified by certain genes.

Read the following scenario to answer the following question. in some zoos, rare crosses between a male lion and a female tiger have produced hybrid offspring called "ligers." male ligers are sterile but some female ligers are fertile. in the wild, lion and tiger ranges do not naturally overlap, making such a cross unlikely. furthermore, the solitary behavior of tigers and the social organizations of lions create behavioral differences. applying the biological species concept, the sterility of ligers reveals that a. lions are probably a subspecies of tigers b. tigers and lions are the same species c. a new species called "ligers" is forming d. tigers and lions are separate species

What causes temperature extremes in the desert

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?