A. can be accurately identified
B. had traits resembling man more than monkeys C. had traits resembling monkeys more than man D. was a very primitive Primate
60.The flesh eating animals are known as ______.
A. Carnivores B. Cetaceans C. Rodents D. Ungulates (3)
In the past ,evolutionary biologists contemplating the absence of wheels in nature agreed that the explanation was not undesirability ;wheels would be good for animals, just as they are for us. Animals were prevented from evolving wheels, the biologist reasoned, by following dilemma: living cells in an animal's body are connected to the heart by blood vessels, and to the brain by nerves. Because a rotating joint is essential to a wheel, a wheel made of living cells would twist its artery, vein, and nerve connections as the first revolution, making living wheels impracticable. However, there is a flaw in the argument that the evolution of wheeled animals was thwarted by the insoluble joint problem. The theory fails to explain why animals have not evolved wheels of dead tissue with no need for arteries and nerves. Countless animals, including us, bear external structures without blood supply or nerves -- for example, our hair and fingernails, or the scales claws and horns of other animals. Why have rats not evolved bony wheels, similar to roller skates? Paws might be more useful than wheels in some situations, but cat's claws are retractable; why not retractable wheels? We thus arrive at the serious biological paradox flippantly termed the RRR dilemma: nature's failure to produce rats with retractable roller skates.
61..Which of the following is the best title for the passage? A. Evolutionary Biology: New Research Meth