Animals in the phylum Platyhelminthes, widely known as flatworms, were the first to develop bilateral symmetry, triploblasty, and cephalization. Bilateral symmetry means that an animal's left and right side of their body are mirror images of each other. Cephalization is the development of nervous tissues becoming concentrated towards the anterior end of an animal. Triploblasty means that an organism has three tissue layers, an ectoderm (outer layer), mesoderm (middle layer), and an endoderm (inner layer). Flatworms do not have a body cavity which makes them acoelomate. During embryonic development the blastopore develops into the mouth, making them protostomes. Flatworms can be parasitic and non-parasitic. Dugesia (planaria) are a group
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Animals in this phylum are commonly known as mollusks. They are triploblastic, protostomes, and have bilateral symmetry. Mollusks have coelomate coelom, mesoderm lines the organs and body cavity. Phylum Mollusca has distinct features, such as a visceral mass, a muscular foot, and a mantle. The muscular foot aids them in locomotion and capturing food. In some cases, like class Cephalopoda, the foot evolved into tentacles. The mantle helps secrete the shell that some animals in certain classes have. In the class Bivalva, animals have two lateral shells attached at the umbo. Mollusks diversity helped them invaded both terrestrial and freshwater …show more content…
During the laral stage, echinoderms display bilateral symmetry. During the adult stage and juvenile stage, they display radial symmetry (body can be divided along central axis). Echinoderms are also triploblastic and coelomate. Instead of being protostomes, the blastopore develop into the anuss, making them deuterostomes. Classes in this phylum are characterized by their arrangement of ossicles, which are hard calcium plates. Part of the body cavity transforms into a water vascular system, a water powered system. Some echinoderms, like sea stars, have arms which contain tube feet. Tube feet help echinoderms by aiding in locomotion and filtering
Animals in this phylum are commonly known as mollusks. They are triploblastic, protostomes, and have bilateral symmetry. Mollusks have coelomate coelom, mesoderm lines the organs and body cavity. Phylum Mollusca has distinct features, such as a visceral mass, a muscular foot, and a mantle. The muscular foot aids them in locomotion and capturing food. In some cases, like class Cephalopoda, the foot evolved into tentacles. The mantle helps secrete the shell that some animals in certain classes have. In the class Bivalva, animals have two lateral shells attached at the umbo. Mollusks diversity helped them invaded both terrestrial and freshwater …show more content…
During the laral stage, echinoderms display bilateral symmetry. During the adult stage and juvenile stage, they display radial symmetry (body can be divided along central axis). Echinoderms are also triploblastic and coelomate. Instead of being protostomes, the blastopore develop into the anuss, making them deuterostomes. Classes in this phylum are characterized by their arrangement of ossicles, which are hard calcium plates. Part of the body cavity transforms into a water vascular system, a water powered system. Some echinoderms, like sea stars, have arms which contain tube feet. Tube feet help echinoderms by aiding in locomotion and filtering