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- Specialized tissues allow more efficient functioning because differentiated tissue types can perform unique functions and work together in tandem to allow the animal to perform more functions. For example, specialized muscle tissue allows directed and efficient movement, and specialized nervous tissue allows for multiple sensory modalities as well as the ability to respond to various sensory information; these functions are not necessarily available to other non-animal organisms.
- Humans have body plans that are bilaterally symmetrical and are characterized by the development of three germ layers, making them triploblasts. Humans have true coeloms, and are thus eucoelomates. Humans are deuterostomes.
- The sponges draw water carrying food particles into the spongocoel using the beating of flagella in the choanocytes. The food particles are caught by the collar of the choanocyte and brought into the cell by phagocytosis. Digestion of the food particle takes place inside the cell. The difference between this and the mechanisms of other animals is that digestion takes place within cells rather than outside of cells. It means that the organism can feed only on particles smaller than the cells themselves.
- Poriferans do not possess true tissues, whereas cnidarians do have tissues. Because of this difference, poriferans do not have a nerve net or muscle cells for locomotion, which cnidarians have.
- In a complete digestive system, food material is not mixed with waste material, so the digestion and uptake of nutrients can be more efficient. In addition, the complete digestive system allows for an orderly progression of digestion of food matter and the specialization of different zones of the digestive tract.
- An advantage is that it is a tough covering that is protective against adverse environments, and predators and parasites. A disadvantage is that it must be shed and regrown for the animal to grow, which requires energy and makes the animal vulnerable during this process.
- Mollusks have a large muscular foot that may be modified in various ways, such as into tentacles, but it functions in locomotion. They have a mantle, a structure of tissue that covers and encloses the dorsal portion of the animal and secretes the shell when it is present. The mantle encloses the mantle cavity, which houses the gills (when present), excretory pores, anus, and gonadopores. The coelom of mollusks is restricted to the region around the systemic heart. The main body cavity is a hemocoel. Many mollusks have a radula near the mouth that is used for scraping food.
- It suggests that the notochord is important for support during locomotion of an organism.
- During embryonic development, we also have a notochord, a dorsal hollow nerve tube, pharyngeal slits, and a post-anal tail.
- Comparison of hagfishes with lampreys shows that the cranium evolved first in early vertebrates, as it is seen in hagfishes, which evolved earlier than lampreys. This was followed by evolution of the vertebral column, a primitive form of which is seen in lampreys and not in hagfishes.
- A moist environment is required as frog eggs lack a shell and dehydrate quickly in dry environments.
- Birds have feathers that streamline the bird body and assist in flight. They also have pneumatic bones that are hollow rather than tissue-filled. Birds are endothermic, which allows for a higher metabolism demanded by flight.
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