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	invertabrates; the evelotion of animals
Darth Vader Big Fish Posts: 338 Kudos: 334 Votes: 35 Registered: 05-May-2005	phylum coelenterata contains a range or lower animals that would most likely have been some of the earliest animals to have evolved from the kingdm protista. coelenterates all have in common the following: all have a digestive system that comes to a dead end sack so food and excretions occur through the same opening they all have 2 and only two 2 cell layers and for this reason it would be correct to say that coelenterates are hollow they all contain tenticals in which the outer layer of cells contain touch sensitive triggers which when activated fire a venemous harpoun in to its victim they are all carnivours(except anthezoas which still eat plenty of meat) so when their victim is paralised it draws the victim into its primative digestive system phylum porifera containing sponges are the most primative of all animals and would fool most people for a plant infact they have no form of locomotion and many biologests classify them as colonial protists sponges feed buy filtering water thuogh their pores and expelling it through the large opening at the top of the organism(s) movment of the water is obtained through flagelum extending from the cells that line the canals within the pores phylum ctenophora has most likely evolved from phylum coelenterata not long after coelenteates became this phylum commonly refered to as comb jellies are similar to coelenterates in that they have tenticals but that is about the only similarity between two phyla comb jellies have a complete digestive track with two openings they don't have a pylop stage in their development unlike coeleterates they also lack stinging cells and compensate by having their tenticals covered in a stiky mucas secreted by the cells that traps prey phylum platyhelminthes other wise known as flat worms are known for their notorius parasitic predeters tape worms and flukes flat worms are divided in to three classes in which only one of which isn't parasitic the other two classes are tape worms and flukes it is beleived that animals evoled from protists in three stages the fist; sponges the second; coelenterats and third; flat worms and it is also beleived that all other animal phyla evolved from flat worms these animals are primative with a digestive track that comes to a dead end sack and actualy alot of flat worms don't have a digestive system and relie on other animals to digest food for them which is the case with tape worms phylum nemertea contains a group of worms known as ribbon worms at first one would think that they are no different to flat worms but but they have a complete digestive track and sensory organs and a basic nervous system with a primative brain. they can live in fresh water or marine habitats and a few live in damp terestrial eviroments. phylum nematoda much like flat worms are mostly parasitic and have few free living species they evolved from ribbon worms though round worms are at the stage of evelotion of animals and at this stage it was race to who could get the best deffence and the best ofence so this resulted in the use of skeletons of which round worms were the first to use skeletons in this case it was a fluid filled cavity with in the body and organs suround this cavity by musule contraction of vairying location rigide posision can be obtained phylum rotifera contains some of the smallest animals that are difficult to see with the naked eye but they are quite complex in structure. they have a complete digestive track with a mouth that is surrounded cillia to draw water and food into the mouth. some biologists say they ere like mid way between arthropods and analids P.S. THIS IS MY WORK NOT PLAGERISM I ACED BIOLOGY IN COLLEGED
Posted 26-Jan-2006 11:27
Darth Vader Big Fish Posts: 338 Kudos: 334 Votes: 35 Registered: 05-May-2005	I WILL FINISH THE ANALASIS OF THE ANIMAL KINGDOM IN DAYS TO COME SO STAY TUNED
Posted 26-Jan-2006 11:27
aquatexan Banned Posts: 151 Votes: 1 Registered: 03-Aug-2004	*evolution
Posted 26-Jan-2006 11:27
Megil TelZeke Fish Addict Posts: 863 Kudos: 890 Votes: 393 Registered: 21-Jul-2003	umm interesting, definetly need to work on some punctuation it very difficult to read. also I believe platyhelminths would be the first to display a simple nervous sytem, since they have a simple nerouvs sytem with a ganglion located on the anterior end, they also have light receptors which would fall under the nervous system. they are evolutionarily speaking more primitive than nemertians and as such would be the first to have a "nervous system". Last edited by Megil Tel'Zeke at 19-Jun-2005 20:47
Posted 26-Jan-2006 11:27


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