Eggs: Not Just for Breakfast
Animals that Hatch from Eggs : When you think of eggs, you might imagine them sunny-side up, scrambled, or turned into a breakfast omelet. But for many animals, eggs are how they give birth to their babies. One way to classify animals is by class. A class is a way to group together animals that have many things in common. For example, fish, mammals, and reptiles are all classes. Usually, animals that are in the same class have babies in the same way: by laying eggs or through live birth. Most mammals, like humans and dogs, have a live birth. Other classes lay eggs. In this lesson, you will learn more about the classes of animals that lay eggs, and some of the exceptions to those rules.
One class of animals is reptiles. Included in the reptile class are snakes, lizards, and skinks. Reptiles all have scales on part of their body and have a skeleton. Also, almost all reptiles lay eggs. Some scientists also include birds in the reptile class because they are very closely related. Scientists believe that birds are more closely related to dinosaurs. Other scientists group birds in their own class called Aves.
Keep in mind, that’s a lot of different species. Imagine how many different types of birds there are, ranging from penguins and ostriches to robins and sparrows that you probably see in your yard. All birds lay eggs, as do crocodiles and turtles. But for snakes and lizards, there are some exceptions.
Some snakes and lizards have live births instead of laying eggs. There are some advantages to a live birth: you don’t need to protect your eggs or keep them warm. This may be why some reptiles that live in colder areas are more likely to have a live birth.
Almost all fish lay eggs, but there are a few exceptions. The sand shark and the ragged tooth shark give birth to live sharks, but other sharks lay eggs. Guppies are another example of a fish that does not lay eggs.