Animal Classification | Evolution | Biology

Animal Classification | Evolution | Biology

All living things are grouped into five kingdoms. In this video, we are going to look at the animal kingdom in more detail. Make sure to watch our video 'Classifying Organisms' first.

There are thought to be over 7.5 million species of animal on planet Earth, of which 900,000 have been described. These are arranged into over 30 phyla, of which these are the nine most common: Porifera, Cnidaria, Platyhelminthes, Nematoda, Mollusca, Annelida, Arthropoda, Echinodermata and Chordata. These are the five main animal phyla: arthropods, annelids, molluscs, nematodes and chordata.

A big question to ask when classifying animals is “Do they have a backbone?” If yes, they are a vertebrate. If no, they are an invertebrate. The chordata contain all of the vertebrates. Not all chordates are vertebrates, but all vertebrates are chordates.

There are many different classes of vertebrate, but the five most well known ones are: fish, birds, amphibians, mammals, reptiles. Each class has different characteristics that defines them, like mammals, which have fur or hair, feed their young on milk and are warm-blooded. Sometimes people aren’t too sure whether something is a reptile or an amphibian. Reptiles have scaly skin, breathe air and usually live on land - except for turtles. Snakes, lizards, turtles, tortoises, crocodiles, and alligators are all reptiles. Amphibians live double lives. They start in water and breathe with gills, and as they grow older they develop lungs, like frogs, toads, salamanders.

Once inside a class - so mammals for example - different species are grouped together in even more detail. There are about 5000 species of mammals, classified into 3 subclasses and about 26 orders.

Now for the invertebrates. Let's go back to the 5 main animal phyla: arthropods, annelids, molluscs, nematodes and the chordata.

Let's look at arthropods in more detail. Arthropods all have a hard exoskeleton and have jointed legs. Spiders are not insects! They are different classes of arthropods altogether called arachnids.

And, just like in animals, these classes break down even further!