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.
An example of an amphibian’s incomplete adaptation to land life is…….
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Lời giải:
Báo saiĐáp án B
Giải thích: Thông tin nằm ở: “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.”
Dịch nghĩa: Một ví dụ về sự thích ứng không đầy đủ của lưỡng cư đối với cuộc sống đất đai là ...
A. cần giữ da ẩm ướt
B. trở lại với nước để đẻ trứng
C. không có khả năng hít thở không khí.
D. vảy bao phủ da