Animals

An animal is any member of the kingdom Animalia. All animals are multicellular organisms, meaning that they are made of many cells. They can move at will, and need food to survive. Animals have senses and a nervous system that enables them to see, hear, smell, and touch the world around them.

Animals are divided into two main groups, or "classes." These are the classes:

1. Invertebrates

2. Vertebrates

Let's go a little more in-depth here with these groups.

Invertebrates have relatively simple in their bodies and inner composition. They have no backbones or internal skeletons; rather, their skeletons are on the outside. Invertebrates make up ninety-seven percent of the world's animal population. Invertebrates are divided into six groups. They are divided into Porifera, Cnidana, Platyhelminthes, Annelida, Mollusca, Echinodermata, and Arthropoda. Porifera is mostly sponges, or coral. Mollusca could be clams, slugs, and snails. All Mollusca have soft bodies. An Arthropod is an invertebrate that has jointed legs. An example of this could be a horseshoe crab. Cnidaria have a sting cellm if it is triggered, they will sting. This is like a jellyfish.

Fish have lived in the Earth's water for over five hundred million years. They breathe underwater using gills, which breathe oxygen that has been dissolved into water. Fish have a network of receptors throughout their bodies, called "lateral lines," that enable the fish to detect currents and sometimes electricity.

Amphibians are known for their semi-aquatic life. That means that amphibians spend some of their life in water and the rest of their life on land. Amphibians need the water because their skin must constantly be moist and they lay their eggs in the water.

Reptiles are the most diverse types of vertebrates in the world. That means that, out of all the animals with a backbone inside of them, reptiles are the most colorful, are many different sizes, and have very different qualities. Reptiles are cold-blooded, and need the sun's warmth to keep them going. They have scaly skin and eggs that look like they are wrapped in leather. Unlike Amphibians, Reptiles can lay their eggs out of the water.

Most birds are able to fly. Birds have feathers of many different colors, and are found almost anywhere on the Earth. Birds are warm-blooded, which means that their body temperature stays around the same temperature no matter how hot/cold it is outside.

Mammals have hair or fur, and their babies are raised on their mother's milk. Mammals give birth to live young, as opposed to their young being born out of eggs. Like birds, mammals are warm-blooded, and live all across the globe.

Guess what? You, a human, are a mammal too!