All matter whether solid, liquid, gas has a chemical formula or elemental symbol.
Filtration may work, there are many types of filters capable of filtering specific types if compounds.
<span>In a dichotomous key you named them by their traits while in a branching diagram it already has the name and it's traits.
</span><span>
Hope this helps :)</span>
Sponges are similar to other animals in that they are multicellular, heterotrophic, lack cell walls and produce sperm cells. Unlike other animals, they lack true tissues and organs, and have no body symmetry.
The shapes of their bodies are adapted for maximal efficiency of water
flow through the central cavity, where it deposits nutrients, and leaves
through a hole called the osculum. Many sponges have internal skeletons of spongin and/or spicules of calcium carbonate or silicon dioxide. All sponges are sessile
aquatic animals. Although there are freshwater species, the great
majority are marine (salt water) species, ranging from tidal zones to
depths exceeding 8,800 m (5.5 mi).
I'm sorry but can you be a bit more specific on these following observations?
