Heather has taught high school and college science courses, and has a master's degree in geography-climatology.
What Is an Arthropod?
What makes you who you are? You might say you could be identified based on your hair color, how tall you are, or that you like to eat pizza.
All of these identifying features you thought of are what we call 'characteristics'. A characteristic is a feature of a person or thing that helps us to identify them from other people or things. Arthropods are a group of animals that share a common set of characteristics.
Characteristics of Arthropods
There are many different types of animals that are grouped together as arthropods. Each animal that is classified as an arthropod has a specific set of characteristics. The most important of those characteristics are:
- Having jointed limbs: All arthropods have jointed limbs. This means their arms or legs can flex and bend at joints. If you imagine human limbs (our arms and legs), we have joints at our elbows, wrists, ankles, and knees. These joints can bend to help us move more easily, and they do the same job in arthropods.
- Being an invertebrate: All arthropods are invertebrates. This means they don't have a backbone. Humans have backbones that help keep us upright. Arthropods don't need to be upright like we do, so they don't need a backbone to survive.
- Having an exoskeleton: An exoskeleton is a hard shell-like cover for the inside parts of the animal's body. Instead of having a backbone, arthropods have an exoskeleton to help give their body a more solid shape and protect their insides. It's also what causes arthropods to make a crunching sound when you step on them.
- Having good senses: All arthropods have very good senses. They have better eyesight than humans because they have more sophisticated eyes. They use their antennae to help them sense motion in the area around them. They have excellent ear-like parts called tympanic membranes that allow them to hear. And they even have a pretty good sense of taste, thanks to the taste sensors in their feet. That's right - instead of tasting food with a tongue like we do, they taste it with their feet!
- Bilateral body symmetry: All arthropods have what is called bilateral body symmetry, which means they're the same on both sides, like you and I are. 'Bi' is another word for two, and that means their body can be divided into two equal parts. 'Lateral' means 'side.' Humans have bilateral body symmetry - if you drew a line from your head to right between your feet, it would be the same on each side.
There are millions of arthropods in the world, and it's a very big category of animals. We can't possibly talk about them all in just one lesson, but to give you an idea, this group includes cockroaches, crabs, and many other sea creatures, butterflies, centipedes, and spiders.
Arthropods are a group of animals that are found throughout the world that have jointed limbs; good senses; an exoskeleton, which is a hard shell-like cover for the inside parts of the animal's body; and bilateral body symmetry, which means you can visually divide their body into two pieces from top to bottom. They also are all invertebrates, which means they don't have a backbone.
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