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July twenty seven, 2008
Cephalopods would be the mollusk category cephalopoda (" head-foot”) and are characterized by bilateral body symmetry and usually a big head (Campbell et 's. 2004). Cephalopods are found in all the oceans with the earth for nearly every depth. None can tolerate freshwater, but those hateful pounds can withstand living in brackish (where sodium and freshwater meet) water. There are two main subclasses of cepahalopds, the coleoidea and the nautiloidea, and are labeled by set up mollusk has a shell. Cephalopods are often regarded as the most clever of invertebrates as they posses large minds complemented by simply well-developed senses. The class developed during the late Cambrian, and early cephalopods were very likely predators near to the top of the foodstuff chain. Their lengthy evolutionary history spans a remarkable 500 million years and has left a huge record of fossils, which makes them an excellent speciment to study and track all their evolutionary history (Vendetti et ing. 2006). Today cephalopods will be eaten throughout the world and are essential to those who have consume all of them. Playing the roll in their particular ecosystem as both predator and food, cephalopods demonstrate to have an important role on earth (Piatkowski et approach. 2001). Features:
There are roughly 17, 000 named types of fossil cephalopods with just 800 species still living. With these kinds of a diverse quantity of species it has been identified that 3 clades have become completely extinct: Endoceratoidea, Actinoceratoidea, and Bactritoidea. Primary will be driven upon both living clades, the coleoidea and the nautiloidea. The coleoidea is characterized by having a great internalized layer or no layer at all, including the octopus, squid, and cuttlefish. The nautiloideas have a covering and this clade includes the nautilus (Vendetti et al. 2006). The greatest number of well-known cephalopods will be members of the coleoids. From the coleoids the squids are the most common and they are characterized by a flexible internal shell called a dog pen, a torpedo shaped physique, and quick movement. The cuttlefish appears similar to a squid but provides a more stout body, a larger internal layer called a cuttlebone, and fins for propulsion. Octopuses are definitely the most progressed of cephalopods and through evolutionary variation have lost their shell, implying successful modifications to their environment. Nautiloids will be characterized by having an external shell, and are among the earliest cephalopods discovered. There is a planispiral covering shape with interconnected internal chambers, enabling the animal to withstand great pressure but resulting in the loss of buoyancy control (Vendetti et approach 2006). One particular prominent characteristic first seen by many regarding the cephalopods is the scale their head compared to the associated with their body system. Surprisingly, these kinds of heads perform in fact hold large brains, and cephalopods are widely regarded as one of the most intelligent invertebrates. With very developed sight and other sensory organs, cephalopods are able to retain information and learn by example or through trial and error. Obtaining the most complex nervous approach to any invertebrate, giant neurological fibers present in the mantle have been a favorite experimental specimen of neurophysiologists for many years (Wood 2006). Cephalopods have great vision, and everything but one particular species see in black and white. This can be strange since cephalopods have the ability to change color in the existence of a predator or when they feel endangered. When changing color they use their particular chromatophores to change brightness and pattern according to their environment. Their ability to blend with their surroundings originates from cells including iridophores and leucophores that reflect light from the environment (Vendetti ou al. 2006). In addition to the highly developed anxious system, cephalopods are the just molluscs having a closed circulatory system. Their vascular system that has two gill minds that approach...
Cited: " Cephalopods. " Biology. By Neil A. Campbell, Her B. Reece and Lisa A. Urry. Boston: Benjamin-Cummings Company, 2004.
" Cephalopods and People. " Octopods Nautilids Cuttlefishes Squids and Family: Cephalopoda. 2 Aug. 08.
Piatkowski, U. A., G. J. Piere, and Meters. M. Cunha. " Effect of cephalopods in the food chain and their interaction while using environment and fisheries. " Fisheries Study 52 (2001): 5-10
Vendetti, Jann. " The Cephalopod. " University or college of California Museum of Paleontology. 06\. 1 Aug. 2008.
Wood, James. " Cephalopod Data source. " Ceph Base. of sixteen June 06\. 1 August. 2008.
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