The continued geographic isolation of Kaibab squirrels from Abert squirrels has allowed the animals to evolve into two distinct subspecies. This is an example of:

A) hybridization.
B) allopolyploidy.
C) adaptive radiation.
D) allopatric speciation.
E) sympatric speciation.

Intraorganizational bargaining is more visible on the union's side because:

A) Unions are essentially political institutions whose agendas are determined by many constituents.
B) Unions are essentially economic institutions whose interest is in self enrichment.
C) Management does not have constituents with competing interests.
D) Management is better at hiding the competing interests of their constituents.

In an Asian rice paddy, carp eat algae around the base of rice plants while a snail scrapes algae from the leaves and stem. The carp and snails can coexist in the same rice paddy because they

A) occupy the same habitat but use the resources differently.
B) occupy the same habitat and use the same resources.
C) use the same resources but occupy different habitats.
D) occupy different habitats and use the resources differently.
E) work according to the competitive exclusion principle.

Muscle tone

A) is a time during which the tissue cannot respond again.
B) results in complete and incomplete tetanus.
C) is a condition in which the muscle fiber only partially relaxes between contractions.
D) is a condition in which stimuli occur so rapidly that there are no intervening relaxations.
E) is a constant tension produced by muscles for long periods of time.

Refer to the accompanying figure. Which organelle evolved from the photosynthetic bacteria?

A) Nucleus
B) Chloroplast
C) Food vacuole
D) Mitochondria
E) Endoplasmic reticulum

Which of the following is NOT a direct effect of parathyroid hormone (PTH) ?

A) Increased Ca²⁺ uptake by the small intestine
B) Increased vitamin D formation in the kidneys
C) Increased Ca²⁺ reabsorption by the kidneys
D) Decreased Ca²⁺ loss by the kidneys
E) All of the choices are direct effects of PTH.