Why is there free oxygen in the air?
A. Evaporation of the oceans liberated oxygen.
B. It is a by-product of photosynthesis.
C. Organisms need oxygen to manufacture ATP.
D. Free oxygen has seeped from cracks in the earth's crust.
E. Free oxygen has been present since the formation of the earth's atmosphere.
Answer: B
You might also like to view...
Most of the significant changes in activities and functions that accompany passage through a cell cycle checkpoint are regulated by the:
A. activation of microtubules. B. changes in membrane polarization. C. activation of kinase enzymes. D. activation of DNA polymerase. E. inhibition of cyclin proteins.
Deinococcus radioduransis (select all that apply):
A. resistant to ionizing radiation. B. able to repair DNA breaks without ATP. C. killed via desiccation. D. unique in its ability to withstand ionizing radiation. E. adapted to withstand the desert environment.
Which of the following type of microscopy would be most effective in visualizing the fine structure of viruses and cytoskeletal filaments 10–25 nanometers in diameter?
A. standard light microscopy B. phase-contrast light microscopy C. transmission electron microscopy D. darkfield light microscopy E. differential-interference microscopy
The subunit of a kidney that purifies blood and restores solute and water balance is called a
a. glomerulus. b. loop of Henle. c. nephron. d. ureter. e. urethra.