Take the right fork in the trail, and you’ll end up above a small waterfall. Here, the rapid trenching of this stream has been delayed by a layer of dolomite. Dolomite is a special form of limestone fortified with magnesium. Not only is dolomite harder than regular limestone, it also cannot be dissolved by slightly acidic rainwater. Dolomite is what created this waterfall and is also the cap rock for our most famous and long-lasting hoodoos.
Echinoderms of the class Asteroidea have arms that are smoothly connected to the body; echinoderms of Ophiuroidea have arms that shoot out from a disk-shaped center. Both are capable of regenerating their limbs when one is broken. In some cases, a lost limb can generate an entirely new starfish. The small protrusions on the top of the starfish are indonesia email list known as dermal gills and are used to absorb oxygen from the water for respiration. Pedicellariae are small appendages used to keep foreign bodies away from the starfish. The madreporite is a hard opening on the aboral side of the starfish used to regulate and filter seawater.
Starfish also have an eye-like structure at the end of each arm, called the eyespot, which is used to detect light.
Hemichordates
Hemichordates are a relatively small phylum. These creatures are extremely important for the study of vertebrate evolution. They are characterized by a body divided into three main areas: the preoral lobe, the neck, and the trunk. Hemichordates are partial chordates and are closely related to early chordates. According to DNA analysis, hemichordates are closely related to echinoderms, which is also evident during observations of the larval stages of the hemichordate and echinoderm. Hemichordates have gill slits, a structure resembling a notochord but called a stomochord, a dorsal nerve cord, and a reduced ventral nerve cord.
