iBT TOEFL Topic Vocabulary Breakthrough Unit 074

iBT TOEFL Topic Vocabulary Breakthrough Unit 074
Author: Li Xiaolai

74. Birds are the only animals with feathers, collectively called plumage, although some other animals, such as insects and bats, also have wings. Nearly all birds can fly, and even flightless birds, such as ostriches and penguins, evolved from flying ancestors. Many characteristics and behaviors of birds are distinct from all other animals, but there are some similarities. Like mammals, birds have four-chambered hearts and are warm-blooded — having a relatively constant body temperature that enables them to live in a wide variety of environments. Like reptiles, birds develop from embryos in eggs outside of the mother’s body.

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