Vertebrates and Invertebrates

Vertebrates:

Vertebrates are the animals with backbones. They are classified into five groups called classes. 

Fish:

Fish are vertebrates with fins. Their skin is covered with scales. They breathe using gills. They lay eggs in the water.

Amphibians:

Amphibians include frogs, toads, newts and salamanders. The adults live on land and breathe using lungs. They have four limbs. They lay eggs in water. The young are called tadpoles, and develop in water where they breathe using gills. Amphibians have smooth skin without scales.

Reptiles:

Reptiles are vertebrates with scaly skins. Most of them have four legs, although snakes have lost their legs. Some reptiles live on land, but some – such as crocodile – live in water. Reptiles reproduce by laying eggs on land. The dinosaurs were reptiles.

Birds:

Birds are vertebrates with wings, feathers and a beak. They lay eggs on land.

Mammals:

This is the group that humans belong to. Mammals are vertebrates with hair. Mammals give birth to live young, which are fed on milk from the mother.

Invertebrates:

Invertebrates are the animals without backbones. There are many different groups of invertebrates. Only a few of them are described here.

Molluscs:

Molluscs are animals with a soft body. They have a muscular foot which they use to move around. Some molluscs have shells. Slugs, snails and octopuses are molluscs.

Annelids:

Annelids are worms with bodies divided up into rings (segments). They do not have legs but they do have tiny bristles called chaetae. Earthworms are annelids.

Arthropods:

Arthropods are invertebrates with joined legs. Their bodies are divided into segments. Arthropods have a skeleton on the outside of their bodies, called an exoskeleton.

Arthropods are the most common kinds of animals on Earth. There are several different groups of arthropods.

Insects: 

Insects are arthropods with six jointed legs. Their bodies are divided into three parts – a head, thorax and abdomen. Each of these parts is made up of several segments. Most insects have two pairs of wings attached to their thorax. The legs are also attached to their thorax. They have one pair of antennae on their head.

Arachnids:

Arachnids are arthropods with eight jointed legs. They do not have wings or antennae. Spiders and scorpions are arthropods.

Crustaceans:

Crustaceans are arthropods with an especially tough exoskeleton. They have more than four pairs of jointed legs. They have two pairs of antennae. Lobsters, water fleas and woodlice are crustaceans.

Myriapods:

Myriapods are arthropods with many pairs of jointed legs. They have one pair of antennae. Millipedes and ccentipedes are myriapods.