Scientists sort the different types of animals in the world into categories based on certain characteristics. Animals are generally grouped into six types of animals. The system for animal classifications is called taxonomy.
The Animal Kingdom
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.
All About Amphibians
All amphibians are vertebrates, and they need moist environments or water to survive.
- They are cold-blooded.
- They absorb water and breathe through their thin skin.
- They have at least one special skin gland used for defense.
- Most follow the life cycle of egg-larva-adult.
Examples of Amphibians
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.
All About Birds
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.
Examples of Birds
Birds are some of the most recognizable animals, and you probably see different types of birds every day.
All About Fish
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.
Examples of Fish
There are over 30,000 species of fish alive today, more than all other vertebrate groups combined.
All About Mammals
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.
Examples of Mammals
There are over 5,500 living species of mammals all over the world.
All About Reptiles
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.
Example of Reptiles
Different species of reptiles can be tiny or huge.
- sea turtles
All About Invertebrates
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.
Types of Invertebrates
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
Examples of Invertebrates
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.