One of the differences between some whales and dolphins is that whales don't provide milk for their young, but dolphins do
although dolphins have lungs for breathing, most whales don't
while all dolphins are warm-blooded, whales are cold-blooded
whales are less aggressive than dolphins and not as big as them
whereas all dolphins have teeth, some whales don't have any
From the information given in the passage, we can infer that dolphins have difficulty surviving in captivity
use only one lung at a time
are among the largest marine animals
don't breathe underwater
cannot survive in climates warmer than their body temperature
One of the special characteristics of the bottle-nosed dolphin is that it is very interested in people
unlike others, it lives in salt water
it is cleverer than most animals
it enjoys being held in captivity
it is an especially studious animal
60 SWIMMING BIRDS OF THE ANTARCTIC Penguin ancestors could fly as well as any other sea bird. Now its wings are short, paddle-like flippers that are entirely useless for flight. The bird has lived for ages in or near the Antarctic regions, where it has few enemies. Thus it came to spend all of its time on land or in the water. For generations it did not fly. In the course of evolution, its wings became small and stiff and lost their long feathers. The penguins, however, became master swimmers and divers. Of all birds, they are the most fully adapted to water. Their thick coat of feathers provides a smooth surface that is impenetrable to water. Their streamlined bodies glide through the water easily. The birds use their wings as swimmers use their arms in a crawl stroke, and they steer with their feet. Penguins can swim at speeds of more than 25 miles per hour.
When they want to leave the water, they can leap as much as 6 feet from the water's surface onto a rock or iceberg.
