He types of living organisms on earth have changed over time-new species have originated and existing species have disappeared. this is an example of

Which parts of the heart prevent backflow of blood in the circulatory system and allow the heart to work like a pump? A.) atria B.) valves C.) ventricles

5. The blob operon produces enzymes that convert compound A into compound B. The operon is controlled by a regulatory gene S. Normally these enzymes are synthesized only in the absence of compound B.

Are artificial sweeteners safe

Which vascular plant organ is most dependent on surface area to carry out its function?

Alternative energy source are always dependent upon favorable weather conditions

Ozone hole refers to ... ? A. hole in ozone layer B. decrease in the ozone layer in troposphere C. decrease in thickness of ozone layer in stratosphere D. increase in the thickness of ozone layer in troposphere

Chemicals used in chemotherapy treatments to fight cancer can also harm cells in hair follicles and bone marrow. What characteristic do these cells most likely share with cancerous cells? A.) They form tumors. B.) They spread through the blood. C.

Binary fission is a process through which A. all cells divide. B. eukaryotic cells divide. C. prokaryotic cells divide. D. cellular DNA is cut in half.

Describe how this algal bloom might alter the local nitrogen cycle in that ecosystem.

What are the reactants in the equation for cellular respiration?