Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
A) Natural selection cannot account for losses, only for innovations.
B) Natural selection accounts for these losses by the principle of use and disuse.
C) Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.
D) The ancestors of these organisms experienced harmful mutations that forced them to find new habitats that these species had not previously used.
Some organisms used as models in genetic research
Richmond, Virginia, lies in ruins in April 1865 at the time of Lincoln’s visit—and a few days before
Time course of HIV infection.
Time course for antibodies to the EBV viral–specific antigens.
BISON: Ceiling of a cave at Altamira
Number of Chromosomes in Selected Organisms