Question 1

Which compound is the best conductor of electricity?

Options :

A : Water

B : Copper

C : Diamond

D : Graphite

E : Silicon

Answer: B

Question 2

Guard cells are kidney-shaped cells surrounding the stomata on the underside of leaves. These cells

change their shape according to the amount of water that exists within them. The more water within, the

more swollen the guard cells are and the stomata open. When water is sparse the guard cells shrivel and

close the stomata. Recent evidence suggests that there are blue-light receptors on the plasma membrane

surface of guard cells that are coupled to potassium (K+) ion channels. K+ ions are normally found in high

concentration outside guard cell membranes when the channels are closed.

What mechanism may account for the fact that guard cells are usually open during the day and closed at

night?

Options :

A :

Photosynthesis uses K+ ions; therefore, lower concentrations of potassium within the leaf drive the

movement of K+ into the leaf through the guard cells.

B :

The presence of sunlight drives K+ into guard cells, while driving water out of the guard cells and

opening the stomata.

C : There is more water in the air during daylight hours than during nighttime hours.

D : K+ ions enter the cell through active transport only when enough water is present.

E :

The presence of sunlight opens the K+ ion channels, driving potassium inside, and causing water to

follow by osmosis, swelling the guard cells.

Answer: A

Question 3

Of the following compounds, which one reacts the most vigorously with water?

Options :

A : HCl

B : Na

C : Zn

D : Fe

E : Li

Answer: B

Question 4

Which of the following statements correctly ex-plains the flow of energy through a food web?

Options :

A : There is more and more energy available as one moves up the food web in order to supply the larger organisms with the energy they need.

B : Organisms of the third trophic level use three times the amount of energy that organisms of the second trophic level use.

C : Radiant energy from the sun is shared equally at all trophic levels of the food web.

D : Energy is recycled through an ecosystem much as carbon and nitrogen are.

E :

There is a step-like decline of available energy from one trophic level to the next as organisms use

energy for activities such as growth and reproduction.

Answer: A

Question 5

A given mass of gas exerts a pressure of 24 cm of mercury at −20° C. What pressure the gas would exert

at 10° C for an isochoric process?

Options :

A : 25.11 cm

B : 24.44 cm

C : 34.45 cm

D :

12.23 cm

E :

26.88 cm

Answer: A