What is the physical basis for the "mitotic clock" , which controls the number of divisions one cell can undertake?

If plant breeders were to breed plants for release of certain compounds that attracted wasps this could help protect the plants from

A. other insects B. herbivores C. certain caterpillars D. All of these are correct. E. None of these is correct.

Which of the following contributes to the removal of organic material in home sewage treatment system leach fields?

A. Entrapment of microbes B. Adsorption of organic material C. Aerobic digestion D. All of these choices are correct.

Sponges can have skeletons made of all these materials except:

a. silica. b. calcium carbonate. c. starch. d. spongin. e. protein.

Which of the following STDs is caused by a virus?

a. HPV infection b. Trichomoniasis c. Chlamydia d. Gonorrhea e. Syphilis