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Flat Earth Academy- Science

Biology: Arthropods- a phylum of the animal kingdom

This is a work in progress... please bear with me, come back and watch it grow? Send constructive suggestions?

What you see below might be seen as an outline for what will eventually be spread across multiple pages.

The arthropods are a phylum (next level subdivision) of the animal kingdom.

Meet the Arthropods

The arthropods phylum is split up into a number of different groups. Except for the insects, these are not actually "classes", which you would imagine to be the case from our simplified outline of nomenclature. Except for the insects, they are actually "sub-phylums", which collect together several similar classes, but you will see what the main classes in each group are. For example, the centipedes form a class, as do the millipedes.

... which we will now consider in more detail


For the natural history enthusiast, I cannot recommend the study of insects too highly. I'd best stop there... for now! Other than to say that you can recognize an insect by its six legs.


Crustaceans have been called "the insects of the seas". They fill, in the sea, many of the niches filled by insects on land.

The crustaceans include crabs, shrimp, lobsters, barnacles.

Krill... a shrimp-like creature... are tremendously important in marine food webs. It is estimated that the weight of all the krill in the world is roughly equal to twice the weight of all the humans in the world. Not bad for an organism which is usually about 1 or 2 centimeters long!


The group's name comes from "myria-", (many), and "-pod", which means "foot". Humans are bipods. Cameras sit on tripods.

There are several classes in the group, but if you start with the centipedes and millipedes, you will have made a good start. They don't literally have one hundred or (strictly speaking "a thousandth") a thousand feet. (Funny... I never noticed that the millipede really ought to be called a "kilopede" until this moment. About 50 years of using a "wrong" term, without noticing!)... but they do have many, and lots and lots of feet, respectively.

Go to the Wikipedia article for many, many fun (well, I found them fun, anyway!) facts about centipedes. A few I can't resist passing on: Some grow to 30cm (about 12 inches). They always have an odd number of pairs of legs. Who knows why! (The millipede article is interesting, too. One millipede has up to 750 feet.)

The chelicerata

This sub-phylum contains classes for...

These organisms all "possess chelicerae which are jointed appendages close to the mouth", hence the group name. I got that bit of information from...


(It isn't one of the important things you "should" know!... but I thought you, too, might be wondering about the name.)

I put the "crabs" in horseshoe "crabs" in quotes to emphasize that these are different from ordinary crabs, which fall into the crustacean group. Horseshoe crabs are believed to have been on earth since more than as long before the heyday of the dinosaurs as there has been time since the beginning of that long heyday. (Horseshoe crabs from about 450 million years ago, dinosaurs from about 160 million years ago, for about 100 million years, in other words.) (Compare that to the idea that humans have been around for about 0.2 million years, if you believe the scientists. Do remember, though, that some people have other beliefs about where the diversity of life came from.)

The arachnids are the various classes of organism with eight legs... the spiders, scorpions, mites, ticks, etc. This might be one of those times when we think "Ick. We could do without them." But no... while some animals (floppy bunnies?) are cuddly, and others are not, everything is an important piece in the overall mechanism. It is wise to fight your natural tendency to think of some groups as unattractive, or worse, "unnecessary". Different creatures are "beautiful" in different ways. But yes, I too find ticks (and the diseases they spread) less cute than bunnies. However, both are worthy of study. (And a wild bunny might well carry disease, too. Cute or not.)

This page is still under construction. Complain if this note hasn't been updated by 22 October? I hope you will agree that what is above is worth something as it stands??

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