Video Transcript
Which of the following statements describes a characteristic shared by amphibians, reptiles, and birds? (A) These organisms all have skin that is covered by scales. (B) The females of these organisms produce milk to feed their young. (C) These organisms all typically lay eggs rather than giving birth to live young. Or (D) these organisms all typically give birth to live young.
The groups of organisms we are being asked about belong to three different classes: Amphibia, Reptilia, and Aves. However, they are all members of phylum Chordata. So they will have some shared characteristics, for example, a notochord and a closed circulatory system comprised of a heart and blood vessels. So let’s take a look at the answer choices to see which one correctly describes a characteristic shared by these three classes.
Class Reptilia includes lizards, snakes, turtles, and crocodiles. The skin of reptiles is covered by dry scales. However, members of Amphibia, which include salamanders, frogs, and toads, have smooth, moist skin. And class Aves, the birds, are covered in feathers. So this statement does not describe a shared characteristic.
The three remaining answer choices involve reproduction. The production of milk to feed offspring is a defining feature of class Mammalia, the mammals. So we can rule out this statement as well. Amphibians, reptiles, and birds typically do not give birth to live young but rather lay eggs. Reptiles and birds lay their eggs on land, often in a nest or other protective structure, while amphibians lay their eggs in water.
Therefore, a statement that describes a characteristic shared by amphibians, reptiles, and birds is these organisms all typically lay eggs rather than giving birth to live young.
