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Phylum NematodaNematoda are more advanced than Platyhelminthes because they have both a mouth for bringing in food and an opening at the other end of their digestive cavity for getting rid of wastes. They have muscles, excretory organs and reproductive organs organized into simple systems. They also have a tough cuticle or waxy outer covering.

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Phylum PoriferaPorifera are made of three simple and independent cells. The first are the collar cells, which line the canals in the interior of the sponge. The second cells are the porocytes, which are cells that make up the pores of the sponge. Finally, the amoebocytes carry out functions of the sponge and help transport nutrients. They also form spicules, which are the sponge’s skeletal fibers. They work together with the collar cells to digest the food for the sponge and produce gametes for sexual reproduction.

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Sponges reproduce sexually and asexually, because it helps keep them alive in their habitats. Most sponges are both male and female. In sexual reproduction, they may play either role. The ‘male’ sponge would release sperm into the water, which would travel and then enter a ‘female’ sponge. After fertilization in the sponge, a larva is released into the water. It floats around for a few days and then sticks to a solid to begin its growth into an adult sponge. Sponges are also able to reproduce asexually through budding. This is when a small piece of sponge is broken off but is still able to survive and grow into another sponge. Sponges are also able to repair damages to their bodies. Sponges are important in nutrient cycles in coral reef systems. They may be important factors to changes in water quality. Also, sponges collect bacteria when they filter the water around them. These bacteria are believed to be able to do many things. First, these bacteria may be able to create forms of nitrogen from the nitrogen gas in the water that may be nutritional for the sponge. They may also be able to turn ammonium from the sponge’s breathing into nitrogen gas that is then released into the atmosphere. This process would lower excess nitrogen levels in coral reefs, also preventing harmful ecosystem changes. Scientists believe that the conversion of nitrogen gas into useful nitrogen is also beneficial to the survival of other organisms in the area. Back to

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Phylum Mollusca

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Mollusks use external gills for respiration. Diffusion also occurs through the moist skin of the mollusks. Most have an open circulatory system (blood is not restricted to circulating within blood vessels), although some have a closed circulatory system. Excretory functions are carried out by a pair of nephridia, tubular structures that collect fluids from the coelom and exchange salts and other substances with body tissues as the fluid passes along the tubules for excretion. The nephridia empty into the mantle cavity. Mollusks have a complex brain, nerves, and a compound eye. Reproduction occurs sexually with separate sexes. Fertilization is external. All mollusks have a visceral mass, a mantle, and a foot. Generally the mollusc phylum can be divided into two classes, the Aculifera (spiny molluscs) and the Conchifera (shell bearing molluscs). Aculifera comprises groups of all those molluscs, that originally do not produce a complete shell. Instead they are protected by a hard exterior skin called a cuticula. This cuticula additionally is protected by calcareous spines.

Phylum Cnidaria

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Cnidarians feed in several ways: predation, absorbing dissolved organic chemicals, filtering food particles out of the water, and obtaining nutrients from symbiotic algae within their cells. Most obtain the majority of their food from predation but some depend almost completely on their endosymbionts and on absorbing dissolved nutrients. Predatory species use their cnidocystes to poison or entangle prey, and those with venomous nematocysts may start digestion by injecting digestive enzymes. The smell of fluids from wounded prey makes the tentacles fold inwards and wipe the prey off into the mouth. In species for which suspended food particles are important, the tentacles and oral arms often have rows of cilia whose beating creates currents that flow towards the mouth, and some produce nets of mucus to trap particles. They produce asexually and sexually. The male and female produce sperm and eggs into the water. The sperm and eggs turn into larva after fertilization. the larva hooks onto rocks and dirt on the bottom of the ocean floor. It turns into a pupa and grows ridges. after time, the ridges break off and turn into medusae. Cnidaria are important to the environment because they filter and clean the water, and they also form symbiotic relationships will other ocean life. Cnidaria possess distinct tissue layers, also cnidaria have a nerve net and porifera don't.

Phylum AnnelidaThe class Oligochaeta live in marine, freshwater and terrestrial habitats. Generally they have a more rounded cross-section, a less distinct head and are less diverse in form than the Polychaetes. They are normally hermaphrodites, and possess a clitellum as adults, an organ which looks like a bandage of skin wrapped around the animal. This clitellum has an important function in sexual reproduction. A few species are parasitic but most species are free living. They also have appendages in the form of pointed bands encircling the dorsal surface of the body.The class Polychaeta are the most diverse group of

the Annelida. They are predominantly marine. Some have well developed heads and complex paddles that they can use for swimming. They are often dorsoventrally flattened. Most polychaetes are either male or female, however some are one sex first and then change to being the other sex. Reproduction is often accompanied by the production of special modified reproductive segments which may become independent of the parent worm before mating. These segments are destroyed or die during or immediately after they have released their gametes.

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The class Huridina are well known for their blood sucking habits and their head to tail looping mode of locomotion. They have 33 body segments, and two suckers which in most cases are located at the head and at the tail. Like the Oligochaeta from which they are believed to have evolved the Huridina occur in fresh water, marine and terrestrial environments.Annelids are more advanced than Nematodes for many reasons. First, they have an obvious head and tail. All segmented worms have one of two types of structures extending from their bodies that are used for locomotion. Most annelids have hair-like and some have fleshy protrusions. Also, annelids have a coelom. The coelom is a space filled with fluid between the gut and the skin. These organs are more complex than the organs in animals in the lower phyla and are organized into more complex systems. For example, the segmented worms have blood vessels which carry food to all of the cells. Nematoda do not have blood vessels. Another organ in the coelom is the nephridium. It is an excretory organ that gets rid of liquid wastes.

Phylum Platyhelminthes

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Adaptations: •have suckers & hooks so that they can attach to the host•have a tough tegument to prevent being digested by the host (tapeworm) or they have a cuticle (flukes)•absent or reduced digestive, circulatory, and muscular systems as they are parasites living inside a host•produce 10’s to 1000’s of eggs to ensure survival•have a complex lifecycle which involves several hosts and different environmental conditions which makes prevention difficult.Most are capable of asexual reproduction, and often pair with other individuals to exchange gametes. A platyhelminthe reproduces by splitting in two. When a flatworm is split up it immediately forms a new flatworm.

Phylum Echinodermata

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In respiration gills on the skin exchange gases. They have an open circulatory system with cilia circulating the fluids through each arm. Amoeboid cells carry wastes out of the body. Echinoderms have a nerve ring around the central disc instead of a brain. Eyespots on the tips of arms sense light. Echinoderms have the ability to regenerate new parts asexually. They also have separate sexes with sex organs in each arm. Sexual reproduction involves releasing gametes into the water (external fertilization).Arthropods are the most advanced invertebrates. Arthropods have exoskeletons, which is lightweight and protects the internal soft body parts. The exoskeleton is waterproof, which allows many arthropods to live on land. Arthropods have well developed nervous systems, they have an open circulatory system and are segmented. Arthropods also have jointed legs that allows many different functions such as swimming, biting, crawling, hopping, flying, jumping, digging and grabbing.

Phylum Arthopoda

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Crustaceans use gills. Insecta, chilopoda, and diplopoda use trachea and spiricles. Arachnids use book lungs. Arthropods have an open circulatory system. They have a dorsal heart and arteries. Crustaceans excrete through nephridia or green glands. Others use a network of Malpigian tubes which collects liquid wastes in the gut. Wastes are crystallized and then excreted to reduce weight for flight. Arthropods have a highly complex nervous system with a brain and a ventral nerve cord. They also have compound eyes, proprioceptors, touch receptors, chemoreceptors, and auditory receptors. Most have separate sexes and internal fertilization. Most undergo some form of metamorphosis.Arthropods have jointed appendages and an exoskeleton. The exoskeleton has three layers. The lipoprotein outer layer provides water proofing. The chitin middle layer provides hard protection. The flexible inner layer allows movement. Like the annelids, their bodies are segmented. The 2 classes are insects and arachnids. Insects have three body segments, six legs, and an exoskeleton. Arachnids have at least eight legs, two body segments, and an exoskeleton.

Bibliography• Ramel, Gordon. "The Annelids (Phylum Annelida)." N.p., n.d. Web. 1 Jun 2010.

<http://www.earthlife.net/inverts/annelida.html>.• "Invertebrate Phyla." N.p., n.d. Web. 1 Jun 2010.

<http://staff.tuhsd.k12.az.us/gfoster/standard/binvert.htm>. • "Cnidaria - Wikipedia, the free encyclopedia." Wikipedia. Wikipedia®, 30 05 2010.

Web. 1 Jun 2010. <http://en.wikipedia.org/wiki/Cnidaria#Feeding_and_excretion>. • "What is the mode of reproduction of cnidarians?." WikiAnswers. Answers

Corporation, n.d. Web. 1 Jun 2010. <http://wiki.answers.com/Q/What_is_the_mode_of_reproduction_of_cnidarians>.

• "Phylum Mollusca." N.p., n.d. Web. 1 Jun 2010. <http://infusion.allconet.org/webquest/PhylumMollusca.html>.

• "Phylum Mollusca." Bio Review Animals. N.p., n.d. Web. 1 Jun 2010. <http://library.thinkquest.org/28751/review/animals/6.html>.

• Khan, Amna. "Phylum Platyhelminthes." DocStoc. N.p., n.d. Web. 1 Jun 2010. <http://www.docstoc.com/docs/451370/Phylum-Platyhelminthes>.

• "Flatworm." N.p., n.d. Web. 1 Jun 2010. <http://www.mcwdn.org/Animals/Flatworm.html>.

• "Further Mollusc Classes." N.p., n.d. Web. 1 Jun 2010. <http://www.weichtiere.at/Mollusks/Andere/haupt.html>.

• "Brief Survey of Animals." N.p., n.d. Web. 1 Jun 2010. <http://www.chs.k12.nf.ca/science/b3201/WebCT-Copy/units/unit2-08.htm>.

• "About Sponges." Tree of Life Web Project. © 2004 Dlloyd, n.d. Web. 1 Jun 2010. <http://tolweb.org/treehouses/?treehouse_id=3431>.

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