Malaria, a disease the infects RBCs, and sickle cell anemia (SCA), a homozygous recessive disease that shortens the life cycle of RBCs, both effect millions of people worldwide. During massive malarial outbreaks, researchers have observed that individuals with a mild form of SCA are more disease resistant when compared to normal individuals within the same population. Which of the following accounts for this finding? (QID 133403)

A. Mild SCA confers a protective effect due to a genetic mutation affecting RBCs.
B. Malaria directly stimulates hemoglobin production by RBC in people with mild SCA.
C. RBCs in non-SCA individuals tend to be less susceptible to malaria-induced
D. Non-SCA individuals tend to consume more malaria-infected grains that make the
disease more potent.

Rattlesnakes make a very distinct hissing and rattling sound when startled or when pursuing prey. Scientists have found that after many years that rattle snakes thriving in areas populated by humans have lost their rattling ability. This observation is likely because…. (QID 133402)

A. humans carry air-borne virus that infect rattle snakes causing muscle paralysis of
their dorsal muscles that cause the rattling.
B. urban development always leads to death and destruction of warm-blooded
desert rattle snakes.
C. habitat destruction caused the selection of evolutionary traits that provide greater
stealthy predatory tactics for protection and catching prey.
D. the entire urban rattle snake population has succumbed to a fatal bacterial
infection which caused the rattle snakes to become paralyzed.

After several centuries, the height of Redwood trees in the densely populated forest have been recorded to be over 300ft tall. Their Redwood counterparts in less densely populated regions of the same forest have only reached height of 200ft. The height of taller Redwood trees is an example of which of the following? (QID 133401)

A. natural selection B. adaptation C. deletion mutation D. phenotypic mutation