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.
Cnidaria: Life History and Ecology. Cnidarian ecology is a complex subject indeed, because it is cnidarians, in particular corals, that are the builders of some of the richest and most complex ecosystems on the planet, coral reefs.Other cnidarians are important as predators in the open ocean. Cnidarians generally occupy two major niches.They may use their cnidocysts to trap prey items. On the other hand, many cnidarians, anthozoans in particular, depend on zooxanthellae, symbiotic dinoflagellates within the tissues, to survive.ther cnidarians are important as predators in the open ocean. Cnidarians generally occupy two major niches. They may use their cnidocysts to trap prey items. On the other hand, many cnidarians, anthozoans in particular, depend on zooxanthellae, symbiotic dinoflagellates within the tissues, to survive.