Why are arthropods invertebrates?

Answer 1

all arthropods are not insects because.. Arthropods aka the Phyla Arthropoda consists of 4 classes. (yr 1 university level here :D ) they are the Crustacea arachnida myriapoda and as you said the insecta. ok so these CLASSES are well defined by the characteristics the organisms of the class bear in common. hence one should not confuse the insect class with the phyla arthropods because one is a main category whilst one is a sub category which aid in defining the main category as a whole. hope this was helpful.

Answer 2

They're invertebrates because they don't have an internal skeleton - like humans and mammals do. Instead, they have an external covering - called an exo-skeleton.
By definition an invertebrate is an organism with no vertebra (backbone, spine). Arthropods don't have them nor need them as they use an external skeleton (exoskeleton) made from a hard protein (chitin), to provide the same functions as internal skeletons (endoskeletons) on vertebrates.

Answer 3

Because they have jointed legs, that's what arthropoda means. Animals that have the same legs are arachnids and crustaceans, the reason why they're also in the groups of the arthropods.

Answer 4

Arhtopods have segmented (jointed) legs, in contrary to other invertebrates like worm.