In the very distant geological past, all animals were aquatic. The very first vertebrates or animals with backbones, of which we have any fossil record, lived in water. These vertebrates, the fish, were adapted to underwater living. Their streamlined bodies were covered with scales to reduce surface friction: they had muscular tails so that they could swim swiftly in such a dense medium as water; and they were endowed with gills for breathing underwater. Descendants of fish-type ancestors crossed the seashore barrier and accommodated themselves to life on land. As amphibians, they possessed limbs instead of fins and lungs instead of gills. But they never became completely free of the bonds that tied them to the water; even today many amphibians return to the water to lay their eggs. Millions of years after the first clumsy amphibians crawled over the land, newer types of land dwellers appeared, these animals give rise to the present-day reptiles and mammals. They were completely converted for land dwelling, with bodies and biological activities far different from those of fish. With these special adaptations, mammals have been able to colonize the woods and meadows, the deserts and high mountains, often far removed from the sea.

Animals found desert living possible only _____

Câu hỏi liên quan

• According to the passage, what does a constricted and harsh voice indicate?

• Broadsides could bs published with little risk to colonial printers because they .........

• The word "their" in paragraph 1 refers to ______.

ZUNIA12

• Which of the following can be inferred from the first paragraph?

• What did researchers discover in the study of honeybees discussed in paragraph 2?

• Which of the following best expresses the main idea of the second paragraph of the passage?

• The word “doubtless” in the passage mostly means ...............

• According to the passage, who was the first person to use artificial refrigeration for a practical purpose?

• According to the passage, all of the followings are TRUE except ___________.

• It’s probable that the next paragraph would discuss ________.

• The word "This" in paragraph 5 refers to .................

• In the paragraph 2, the word “accomplishments” can be best replaced by ..............

• The word “they” refers to ................

• According to the passage, what causes the unique color and look of hummingbirds?

• The underlined word “sophisticated” in paragraph 1 can be best replaced by ...............

• Which of the following would be the best title for this passage?

• According to the text, Marrination, when built, will be a(an)__________ city.

• According to the passage, the highest amount of pheromone vapor is found ........

• What is the setting of Tolkien's trilogy?

• According to the passage, when James Monroe came to the White House, it had been .......