There are two main types of animals: vertebrates and invertebrates. Invertebrates, which are animals without backbones are divided into different classes, like arachnids and insects. There are five main classes of vertebrate animals. These are birds, mammals, fish, reptiles and amphibians. Each of these classes of animals have distinct characteristics that distinguish from the other classes of vertebrates. For instance, mammals are distinguished as having mammary glands, birds are born out of hard-shelled eggs and have feathers, fish have gills, fins and scales and live in water, reptiles are cold-blooded, live on land, and have scaly skin, while amphibians are distinguished as having gills when they are young and hence living in water, but having lungs when they mature and hence living on land.
Similarities Between Birds And Mammals
Birds and mammals share certain characteristics that have led some people to believe that they belong to the same animal class. For instance, some people erroneously believe that the main distinguishing feature of birds is that they have wings, and since bats have wings and are mammals, then to them it follows that birds are mammals. However, this logic is flawed since, as we have already established, birds are not distinguished as birds because they have wings, but because they have feathers and are born out of hard-shelled eggs. Furthermore, both birds and mammals are warm-blooded, a feature that separates them from the other vertebrate classes. Birds and mammals both also have four-chambered hearts with two ventricles and two atria, a model that enables them to have different pathways for oxygenated and deoxygenated blood, unlike, for example reptiles in whose bodies oxygenated and deoxygenated blood sometimes flow through the same chambers, hence leading to an efficient system of blood circulation. Furthermore, birds and mammals are the only animal classes that feed and care for their younger when they are still young, as the other animals leave their young to care for themselves.
Differences Between Birds And MammalsHowever, while all is said and done, there are a couple of features that distinguish birds from mammals. For instance, while birds lay eggs, mammals give birth to their young live. Thus, while the duck-billed platypus has many features that a lot of birds have, because it gives birth to live young and does not lay eggs, it is a mammal and not a bird. Moreover, while mammals feed their young by giving them milk from their mammary glands, birds feed their young by chewing, swallowing and regurgitating into their mouths partially-digested food. Furthermore, while birds have feathers to keep them warm, for mammals this function is performed by their hair and fur. In addition, because birds need to fly to move from one place to another, their bones are porous and less dense than those of mammals who have thicker and more dense bones. Another fundamental difference between birds and mammals lies in how they produce sound. While both classes of animals have a larynx, only mammals use this organ to produce sound. Birds, on the other hand, produce sound through their syrinx. Lastly, one can distinguish birds from mammals by pointing that while birds have wings, the limbs of mammals end in paws, hands and hooves.