Do you've any idea about how many animal species are there on Earth? There are as many as 30 million animal species alive. It always excites a person to learn more about these species, but it's pretty a challenging task too. As there's giant number of species, it becomes hard to bear in mind each one of them. So, to possess a clearer idea, you can segregate these species of animals into 6 fundamental classes.
Invertebrates are the first animal species group. The name of the category itself shows that invertebrates don't have a vertebral column or a spine. Most of the back pain sufferers might as well wish that they were born without a spine too. Flatworms, microorganisms, insects and so on are some of the species, which come under this category.
Another well known animal group is formed by fishes. Fishes are the 1st vertebrates that have evolved. These species may be additionally classified into three divisions that are cartilaginous fishes, lobe finned fishes and ray finned fishes. Ray finned fish is one of the most versatile kinds of fish that has 24,000 species. Fishes make a brilliant alternative for pet, other than a pet dog.
Another broad category of animal is amphibians. These are the animals that live both- on land and water. The 1st amphibians developed from lobe finned fishes, approximately 370 million years ago. Approximately, there're 5000 to 7000 species of amphibians. Some animals that fall in this category include frogs, salamanders and the like.
Reptiles, is another considerable category of animals. By essence, they are cold blooded vertebrates. There are two different characteristics of reptiles. First of all, they have scales on their body and 2nd they lay hard eggs. The 1st amphibians date back to 340 million years ago. Crocodiles, turtles, tuataras and squamates are some examples of reptiles.
Mammals is maybe the most evolved category of animals. They inhibit a diverse selection of characteristics and may adjust themselves to a wide variety of habitats. There are at least 5,400 species of animals alive today. Mammals are extremely diverse. They range from the tiny Bumblebee Bat, that is three centimeters to the blue whale, which is 33 cm long. Did you know that human beings are also mammals?
When we talk about animals, we also talk about birds. There are many birds that are animals and that can even fly. Moreover, birds have specific characteristics that make them different from the others. These features are furcula, feathers, bills, etc. Flying birds give a sense of contentment. So, bird watching is a hobby for a lot of people. You can also enjoy bird watching, with no worries regarding sun tan.
Gaining knowledge about species of animals is an enriching experience for sure.
![[Valid RSS feed]](http://www.look4articles.com/images/icon_Rss.png "XML Feed For RSS"){kind=icon}
Category Rss Feed
Print This Article
Add To Favorites
![[Valid RSS feed]](http://www.look4articles.com/images/rss.jpg "XML Feed For RSS")