Eventually, I replaced it with a full-size tire, but I've always wondered why manufacturers say you shouldn't use the spare for longer than necessary. Since the spare tire is used so infrequently, carmakers have switched to narrow, compact spares to save space and weight. Of course, a spare tire is a lifesaver when regular tires go pop, but leaving the temporary tire on for longer than the manufacturer recommends invites a host of problems. First, a temporary spare isn't as durable as a normal tire.
Cells have become specialized and form true tissues and cnidarians are the first group to have B nerve cells organized into a nerve net B sense organs (statocysts and ocelli) B extracellular digestion Cnidarian Body Plan The diploblastic cnidarians are radially or biradially symmetrical with oral and aboral ends.
One of the most important distinguishing characteristics of the phylum are the Nematocysts. Nematocysts, and their enclosing Cnidocysts come in about 24 different forms, the differences play a functional role in the classification of the phylum. A Cnidocyst is a cell that secretes a nematocyst within it.he word Cnidaria refers to Cnidocysts, specialised cells which contain the Nematocysts, the stinging organelles that allow the Cnidaria to subdue their prey. The Cnidaria are the oldest of the true metazoan phyla.