2. You have probably seen at least one movie where aliens invade the earth and humans find
that their weapons are of little use in defending themselves against alien technology. In the end,
the world (usually led by the United States) has finally figured out how to adapt human
technology to defeat the invaders. In nature, we find a similar situation when humans transport
an alien (nonnative) species from its natural ecosystem to a new one. However, unlike in the
movies, the original species in nature frequently loses the war for survival and is overcome by
the aliens. Choose the reasons that help explain why a native animal species might not survive
when an alien species is introduced into its ecosystem. Which is NOT a possible reason among
the choices?
A. Unlike humans, animals cannot change their behavior or learn how to defend themselves.
B. An animal may not recognize that an alien is a threat to its survival until it is too late.
C. Since the alien is new to the ecosystem, there may not be a mechanism (e.g., predator,
parasite, competitor) to control growth of the alien species. Therefore, the alien may be able to
quickly increase its numbers, overwhelming resident species.
D. Animals are adapted only to those pressures and threats that their ancestors experienced
over many generations. They cannot quickly change their anatomy or physiology to respond to
a new type of alien attack.
