Today, the major danger to species is

A) hunting by humans.
B) introduction of exotic species.
C) destruction of habitats.
D) predator control.
E) commercial harvesting.

At the end of the NFL lockout of referees, the NFL could have kept the replacement referees on staff without hiring back the union referees if they had wanted to do so.

Hoverflies are attracted to sweets at outdoor picnics. The reaction of humans is usually to flee because of the flies' uncanny resemblance to bees. The survival of hoverflies is enhanced by ____.

A) mimicry
B) camouflage
C) warning coloration
D) chemical defenses
E) display behavior

How does a sperm penetrate an egg?

A) Enzymes in the acrosome dissolve the zona pellucida.
B) The sperm binds to a receptor protein in the membrane and this initiates endocytosis.
C) The forward pressure of the flagellum forces it through the plasma membrane.
D) Spermatids are wedge-shaped and are chemically attracted to the inside cytoplasm of the egg cell.
E) The haploid sets of chromosomes match across the membrane and this triggers the membrane to dissolve.

Diagram a flower, labeling the parts, and identify the part(s) that possess the functions described in the following list:
A) male reproductive organ, b) female reproductive organ, c) attracting a pollinator, d) point of attachment of flower parts, and e) bud protection.

Which of the following events would occur when the environmental temperature is considerably lower than body temperature?

A) Sweating
B) Vasoconstriction of the blood vessels of the skin
C) Increased heat loss through the skin
D) Decreased muscular activity to maintain heat
E) Vasodilation of the blood vessels of the skin