All animals belong to a biological kingdom called kingdom Animalia. This kingdom is then broken down into over 30 groups, or phyla (plural form of phylum). About 75% of all species on Earth are animals. Animals are then broken down into two types: vertebrates and invertebrates.
- Animals with a backbone are vertebrates.
- Vertebrates belong to the phylum called Phylum Chordata.
- Vertebrates are further broken down into five classes: amphibians, birds, fish, mammals, and reptiles.
- Animals without a backbone are invertebrates.
- Most invertebrates are in the phylum Arthropoda.
You can find examples of amphibians all around the world. In some cases, examples of amphibians seem like the same animals, but they can be quite different like a frog and a toad.
Birds are a type of warm-blooded vertebrate that are adapted to fly.
- Not all birds can fly, but they do all have wings.
- Birds have beaks that help them catch and swallow food.
- The digestive system of a bird allows it to eat whenever it can and digest the food later.
- Birds lay eggs to reproduce.
- They are endothermic, meaning they maintain their own constant body temperature.
- They are bipedal, which means they have two legs.
- They have hollow bones and their bodies are covered in feathers.
- Birds belong to the class called Aves.
Fish are also vertebrates, and they are considered the oldest-known vertebrates.
- They are ectothermic, or cold-blooded, which means they rely on their surroundings to regulate their body temperature.
- Fish have fins.
- Most, but not all, fish have bodies covered in scales and breathe through gills.
- Fish live underwater.
There are over 30,000 species of fish alive today, more than all other vertebrate groups combined.
Mammals are another type of vertebrate that belong to the class Mammalia.
- Young mammals get nourishment from milk produced by their mothers.
- Most mammals have hair.
- Their jaw is hinged directly to their skull, unlike all other vertebrates.
- Almost all mammals give birth to live babies.
- They are endothermic, or warm-blooded.
There are over 5,500 living species of mammals all over the world.
Reptiles are thought to be the first vertebrates to live completely on land. But, not all reptiles live only on land today.
- They are cold-blooded, or ectothermic.
- They lay eggs to reproduce.
- They have four legs or are descended from animals with four legs.
- They breathe through lungs.
- Their bodies are covered in scales or scutes.
Different species of reptiles can be tiny or huge.
- sea turtles
Approximately 95% of all animals are invertebrates. Invertebrates do not have a backbone. There are different types of invertebrates, but they all share a few characteristics.
- They are made up of many cells that work together or are multicellular.
- Most, but not all, have tissues, cells that work together in a more complex way.
- Most, but not all, can move.
- There are over 35 phyla of invertebrates.
- They generally have soft bodies.
There are eight phyla of invertebrates that are alive today.
- annelida - have a segmented body and primitive brain
- arthropoda - have jointed appendages and an exoskeleton
- cnidaria - have tissues and an incomplete digestive system
- echinodermata - have some type of spiny structure on their outside
- mollusca - generally have soft bodies and a hard exoskeleton
- nematoda - unsegmented with worm-shaped bodies
- platyhelminthes - soft, ribbon-like worms with no respiratory system
- porifera - multicellular organisms living in water with no organs or tissues
Most invertebrates are insects, but there are over one million species of invertebrates in the world.
- anemone (cnidaria)
- clams (mollusca)
- coral (cnidaria)
- crabs (arthropoda)
- earthworms (annelida)
- flatworms (platyhelminthes)
- insects (arthropoda)
- jellyfish (cnidaria)
- leeches (annelida)
- roundworms (nematoda)
- sea urchins (echinodermata)
- snails (mollusca)
- spiders (arthropoda)
- sponges (porifera)
- squid (mollusca)
- starfish (echinodermata)
- tapeworms (platyhelminthes)
While all animals have a few things in common, they are a very diverse group of living things. You can learn more about animals by exploring things like names for groups of animals or even the names of animals in Spanish. You can learn about other living things by checking out the different types of plants in the world.