Phylum Porifera Essay Example for Free

Phylum Porifera EssayWhich phyla lack organs? What type of symmetry do they capture?Phylum Porifera which lacks any symmetry (asymmetry) and phylum Cnidaria which has radial symmetry.List each of the phyla that show cephalization.Phylum Annelida, Phylum Mollusca, Phylum Arthropoda, Phylum Platyhelminthes, Phylum Nematoda, and Phylum Chordata.Do all organisms on the table have 3 germ layers (endoderm, ectoderm, and mesoderm)? If not, which Phyla have fewer than three germ layers? non all the organisms have three germ layers. The organisms with less than three germ layers belong to Phylum Porifera which has no received germ layers and phylum Cnidaria which has two germ layers (diploblastic). One phylum has more species than all the others. State the call up of this phylum and provide several different examples of species found in this phylum.Phylum Arthropoda. Examples of species in this phylum include Brazilopelma colloratvillosum, Dermacentor variabilis, Limulus polyphemus, C olossendeis megalonyx, Branchinecta gigas, Pyromaia tuberculata, Asterocheres echinicola, Narceus americanus, Scaphiostreptus parilis, and genus Musca domestica.According to chapter 24, tip do not all have the same otiose bodily structure. Describe the differences among fish from the most primitive to more advanced types.Fishes greatly differ in their anatomical features especially their skeletal structures. The most primitive group of fishes based on skeletal structure is cognize as segmentation Agnatha and the fishes in this class ar referred to as the jawless fishes. These have a cartilaginous indispensable skeleton which means that they have no unbent bones (Layman, 2003). They also lack true teeth, true jaws, and true vertebrae (Layman, 2003).The other group of fish is referred to as the cartilaginous fishes and they belong to a class of fishes cognize as Chondrichthyes. Their skeleton is made up of cartilage. Unlike the jawless fishes, fishes in this group have jaws and true teeth which are careworn as is seen with sharks (Layman, 2003).The final group of fish is known as the atrophied fishes and fishes in this group belong to a class known as Osteichthyes. These fish are really advanced and unlike the other two groups, fishes in this group have a skeletal structure that is made of true bones meaning that their skeletal structure is mineralized (Layman, 2003). They have a bony jaw, bony teeth, and bony vertebrae (Layman, 2003).Describe the three types of mammals based on how their unfledged extend?One group of mammals is referred to as placental mammals. The young ones of mammals under this group develop for long wrong their mothers. This prolonged development is facilitated by the forepart of an allantoic placenta (Go Pets America, 2010). This placenta allows close contact between the vascular systems of both the mother and the growing embryos and this ensures that the embryos are adequately and continually nourished (Go Pets America, 2010). The placenta also allows for removal of waste products from the womb. In addition, the embryos are protected inside their mothers. For example the body temperatures of the mothers are usually constant and this protects the developing young ones from the harsh surroundings. These conditions provide a conducive environment which allows for development of the young ones to a very high degree.The other group of mammals is known as marsupial. The young ones of mammals under this category develop in the womb just like in placental mammals but their period of development is short. The reason for the short development period is due to presence of a yolk placenta whose ability to nourish the fetus is limited (Vaughan Ryan, 2010). After birth, the undeveloped young ones hold out their development inside their mothers pouches where they cling to the mothers nipples with their mouths (Vaughan Ryan, 2010). The young ones get fed on milk through the nipples.The final group of mammals is referred to as monotremes. Mammals in this group reproduce by laying nuts. With these mammals, two eggs are laid each time and the young ones grow inside the eggs for a short time before they are hatched (Vaughan Ryan, 2010). Inside the eggs, the young ones are nourished by use of egg yolk. The hatched young ones are always very immature at birth and they continue to develop by feeding on milk from their mothers. But unlike the other groups of mammals, these mammals lack teats and milk oozes from the mothers abdomens and the young ones feed by licking the oozing milk (Vaughan Ryan, 2010).