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Animal Kingdom Two Types 1)Invertebrates- do not have a backbone 2) Vertebrates- have a backbone Cell specialization Every animal starts out as a blastula- a ball of cells. The ball folds in on itself and forms a single opening called a blastopore. The blastopore leads into a central tube that runs the length of the embryo. This tube will become the digestive tract. Two types of central tubes 1) Protosome- is an animal whose mouth is formed from the blastospore. 2) Deuterosome- is an animal whose anus is formed from the blastospore. Embryo development The cells that form from the blastula form three distinct layers. A) Endoderm- the intermost germ layer, these cells become the digestive tract and the respiratory system B) Mesoderm-the middle layer, becomes the muscles, the circulatory, reproductive and excretory system C) Ectoderm-the outmost layer, becomes the sense organs, nerves and out layer of skin Phylum Porifera • Sponges are the simpliest animals • The word “Porifera” means pore-bearers • Water flows into and out of tiny pores (go in ostia and go out oscula) all over their bodies. • Food comes in with the water (dissolved nutrients) Why are Sponges animals? Sponges are classified as anumals because they are multicellular, heterotrophic, have no cell walls and contain a few specialized cells Characteristics of Sponges 1) Multicellular 2) Body with pores that serve as a passage for water. 3) Mostly marine, all aquatic (habitat) 4) Mostly epidermal cells with Choanocytes on the inside. These are cells with flagellum that create water currents Characteristic (cont.) 5) Simple skeletal structure made of spiny spicules (spike shaped structure made of chalk-like calcium carbonate or glass-like silica) Spicules are made by archaeocytes; specialized cells that move around within the walls of the sponge. 6) No true organs or true tissues 7) Digestion happens intercellularly Characteristics (cont) 8) Excretion and respiration by diffusion 9) Most likely no nervous system—no response to stimuli 10) Asexual reproduction by buds and sexual reproduction by eggs and sperm; free swimming ciliated larvae Habitat and protection Sponges are important in aquatic type environments. They are sessile, which means that they stay put. Their structures are varied so they can become homes for other organisms. They commonly practice mutalism, a situation in which both partners benefit Some sponges provide protection to small organisms while others contain photosynthetic organism that need sunlight to thrive. Some spicules have a cross-shaped antennae which directs sunlight to the photosynthetic parts like a magnifying glass or lens. Predators Sponges thrive because they have few predators. They also have a noxious odor which makes sampling them unpleasant. Because of their skeleton in would be like eating splinters of glass. Classes of Sponges Calcarea- calcium carbonate spicules Hexactinellida- six-rayed silica containing spicules Demospongiae- skeleton made of silica or spongin (specialized collagen) Sclerospongiae- contain massive amounts of calcareous (calcium carbonate) skeleton with silica spicules.
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