What are proteins that are needed to lower the amount of energy required to start chemical reactions?

What is the function of nucleic acids

Which of the following sex and generation combinations directly produces the pollen tube of angiosperms? a) male gametophyteb) female gametophytec) male sporophyted) female sporophyte

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