The gate control theory of pain says that pain impulses traveling through the lateral spinothalamic tract can be suppressed by increased activity of the

A) anterior spinothalamic tract.
B) tertiary neurons.
C) extrapyramidal tracts.
D) dorsal column/medial lemniscal system.
E) spinocerebellar tracts.

In the blood, most (60%) of the carbon dioxide moves through plasma as which of the following substances?

A) Bicarbonate
B) Lactic acid
C) Carbonic acid
D) Formic acid
E) Acetate

Bundle scars would be found within a leaf scar.

What best describes the location where sexual spores form in club fungi?

A) in gills of the mushroom
B) in club-shaped cells at the gill base
C) in fruiting bodies
D) in club-shaped cells of mycelium
E) in hyphae of an embryonic mushroom

The closest living relatives of tetrapod include

A) coelacanths.
B) lungfishes.
C) telosts.
D) a and b
E) all of the above

Describe the vertebrate adaptations to terrestrial life.

In the process of double fertilization, one sperm fuses with the egg and the other sperm fuses with a spore.

A group of cacti on a sun-exposed slope have greater reproductive success than cacti on a shaded slope. The habitat on the sun-exposed slope can be classified as which of the following?

A) r -selected habitat
B) K -selected habitat
C) Both an r -selected and a K -selected habitat
D) Sink habitat
E) Source habitat