Name and briefly describe two traits that amphibians and reptiles share that are not common to all vertebrates
Two traits that amphibians and reptiles share but are not common to all vertebrates are 1) the presence of a three-chambered heart and 2) the ability to lay eggs.
1) To address the first trait, we need to understand the general classification of vertebrates. Vertebrates belong to the phylum Chordata, and they are characterized by having a notochord, a dorsal hollow nerve cord, pharyngeal slits or pouches, a post- tail, and segmented muscles. This phylum includes not only reptiles and amphibians but also fish, birds, and mammals.
When it comes to the circulatory system, vertebrates can have either two, three, or four chambers in their hearts. Reptiles and amphibians have a three-chambered heart, which consists of two atria and one ventricle. This characteristic allows for separation of oxygenated (oxygen-rich) and deoxygenated (oxygen-poor) blood to some extent, but there is still a mix of both types of blood in the ventricle. In comparison, mammals and birds have a four-chambered heart, where the oxygenated and deoxygenated blood is completely separated, resulting in more efficient oxygen delivery to the body.
2) Moving on to the second trait, the ability to lay eggs, we can see that not all vertebrates lay eggs. This reproductive method, known as oviparity, involves the female producing and laying eggs externally, where the embryos develop and hatch outside the mother's body.
Amphibians and reptiles both fall under the category of oviparous animals. Amphibians, such as frogs and salamanders, lay their eggs in water or moist environments, allowing the eggs to be protected from dehydration. Reptiles, such as snakes and turtles, also lay shelled eggs, but they can do so in a wider range of environments, including on land.
In contrast, other vertebrates, such as mammals, birds, and some fishes, have different reproductive strategies. Mammals give birth to live young through internal development and nourishment via a placenta, a process called viviparity. Birds also lay eggs, but their eggs have a hard shell and are incubated by the parents until they hatch. Fishes, on the other hand, can be oviparous (lay eggs) or viviparous (give birth to live young), depending on the species.
So, while the traits of having a three-chambered heart and laying eggs are shared by both amphibians and reptiles, they are not common to all vertebrates.