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Posted on March 19th, 2013, by

A phylum is a category bellow kingdom and above Class in biological grouping, particularly of animals. At the most fundamental level, a phylum may be characterized in two courses: “as a group of organisms with a certain degree of morphological or developmental similarity (the phenetic definition), or a group of organisms with a certain degree of evolutionary relatedness (the phylogenetic definition)”¯ (Veterinary Dictionary). A Phylum depicts the biggest scientific classifications of life forms. Phyla may also be regarded as the same universal body plan, group sharing, which comprises both the external appearance, but is more significantly contingent of the body’s internal organization.

There are 36 acknowledged animal phyla, but nine (Porifera, Mollusca, Platyhelminthes, Cnidaria, Nematoda, Chordata Arthropoda, Annelida, and Echinodermata) include the huge majority of depicted, present species.

Body plan is one access to define phyla. Development of the body plan is assumed by huge and complex gene regulatory networks. Different components of these networks bring out at various levels and in many ways, and are very much contingent on selection compressions from changeable environments.

Key words: phyla, symmetry, cephalization, skeleton, layer.
Which phyla lack organs? What type of symmetry do they have?

Cnidaria and Porifera are those couple of phyla that lack organ systems and organs. The Porifera lacks an enclosed body tissues, cavity, organs, and neural network. Symmetry that Porifera species hold is irregular. The Cnidaria lacks an enclosed cavity of a body. Cnidaria’s symmetry is radial. The platyhelminthes lack the enclosed cavity of a body, and organs specified for circulatory system and also for gas exchange. Their symmetry is bilateral symmetry. The nematode lacks system of circulation. They have bilateral symmetry. Some mollusca lack exoskeleton as the cephalopoda class. Mollusks lack a closed circulation exclude for cephalopoda class. Some “do not have their gills or the gills are secondarily lost. The mollusks have bilateral symmetry”¯ (Scott).
List all of the phyla that show cephalization? Most of the phyla that hold bilateral symmetry also hold cephalization. These comprise: Phylum arthropoda, Phylum mollusca, Phylum platyhelminthes, chordate or Phylum vertebrae.

Do all organisms on the table have 3 germ layers (endoderm, ectoderm and mesoderm? If not, which Phyla have fewer than three germ layers?
Not all organisms have 3 germ layers. The next Phyla have less than 3 germ layers: Porifera ”“ any germ layers at all, Cnidaria ”“ 2 germ layers. “One phylum has more species than all the others”¯.
One phylum has more species than all the others. State the name of this phylum and provide several different examples of species found in this phylum.

Phylum arthropoda has the majority of various species among others. Kinds that belong to these phylum are the following: “dragonfly, damselfly, grasshopper, katydid, cricket, mantis, cockroach, walkingstick, termite, true bug, leafhopper, cicada, aphid, scale insect, beetle, butterfly, moth, fly, mosquito, flea, bee, ant, wasp and many more”¯ (Scott).

Fish do not all have the same skeletal structure. Describe the differences among fish from the most primitive to more advanced types.
Fishes have various spinal columns. The spinal column of fishes compasses from the most primeval to the most complicated. Various spinal columns contain the most primeval notochord, the cartilaginous spinal column of the chondrichthyes. Fishes also have various skulls. According to the skull there are three fish types: “the jawless fish, cartilaginous fish and bony fish”¯. Fish can also be grouped according to skeleton: osteichthyes and chondrichthyes.

Describe the three types of mammals based on how their young develop?
Three types of the mammals based on how their youth develops, are monotremes, marsupials and placentary mammals


Work Citied
Scott, N. Study Guides. The Skeletal System. (2004) Montana State University.
Saunders Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. (2007). D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier.


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