Biology 2015

A nutrient element is considered essential if
a. plant growth increases with a reduction in the concentration of the element.
b. plants die in the absence of the element.
c. plants can substitute a similar element for the missing element with no ill effects.
d. the element is a positive ion.

Humus
a. supplies nutrients to plants.
b. is basic in its pH.
c. is found in the deepest soil horizons.
d. is inorganic in origin.

Soils rich in which type of mineral particle will have a high waterholding capacity?
a. sand
b. silt
c. clay
d. All soil particles hold water equally well.

Negatively charged clay particles attract
a. $\mathrm{K}^{+}$.
b. $\mathrm{NO}_{3}^{-}$.
c. $\mathrm{Ca}^{2+}$.
d. Both a and b are correct.
e. Both a and c are correct.

The Casparian strip affects
a. how water and minerals move into the vascular cylinder.
b. vascular tissue composition.
c. how soil particles function.
d. cation exchange.
e. Both a and c are correct.

Nitrogen-fixing bacteria
a. reduce atmospheric nitrogen.
b. can live independently in the soil.
c. are usually associated with legume plants.
d. break $\mathrm{N}=\mathrm{N}$ bonds.
e. All of these are correct.

Which of the following is not an adaptation by plants to obtain minerals?
a. specialized leaves that capture insects
b. parasitic plants, such as a dodder
c. mycorrhizal associations
d. nitrogen-fixing bacteria in root nodules
e. broad leaves in low sunlight

The opening in the leaf that allows gas and water exchange is called the
a. lenticel.
b. hole.
c. stoma.
d. guard cell.
e. accessory cell.

Stomata are usually open
a. at night, when the plant requires a supply of oxygen.
b. during the day, when the plant requires a supply of carbon dioxide.
c. day or night if there is excess water in the soil.
d. during the day, when transpiration occurs.
e. Both b and d are correct.

What role do cohesion and adhesion play in xylem transport?
a. Like transpiration, they create a tension.
b. Like root pressure, they create a positive pressure.
c. Like sugars, they cause water to enter xylem.
d. They create a continuous water column in xylem.
e. All of these are correct.

After sucrose enters sieve tubes,
a. it is removed by the source.
b. water follows passively by osmosis.
c. it is driven by active transport to the source, which is usually the roots.
d. stomata open so that water flows to the leaves.
e. All of these are correct.

The pressure-flow model of phloem transport states that
a. phloem content always flows from the leaves to the root.
b. phloem content always flows from the root to the leaves.
c. water flow takes sucrose from a source to a sink.
d. water pressure creates a flow of water toward the source.
e. Both c and d are correct.