What’s the differences between the three main classes of sponges.

There are three classes. These classes include Calcerea, Desmospongia, and Hexactinellida. They are divided into these classes based mostly on the composition of their spicules and skeletal fibers. (spicules are rod-shaped cellular projections that make up the skeleton of sponges) hope this helps!

Explanation:

the  frequency of a wave represents  the number of wavelengths that pass a specific point per second. the unit for  frequency  is hertz (hz).

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igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

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