Characteristics Porifera Cnidaria Platyhelminthe s Rotifers Mollusca Annelida Nematoda Arthropod a Echinoder mata Example Sponge hydra Flatworms Pararotatoria Bivalvia Earthworm Enoplea Limulus polyphem us (King Crab) Asterias (Starfish) #of tissue layers two thin layers Have diploblastic tissues triploblastic, triploblastic (contain three germ layers.) Body has more than two cell layers, tissues and organs. triploblasti c. triploblasti triploblasti triploblasti c. c. c. Tissue /organ system present? no organs or true tissues have no organs like hearts or lungs have organ systems, including an excretory, digestive Specialized organ systems and complete digestive tract Has gaseous exchange organs called ctenidial gills. they exhibit organ system grade of organisatio n, showing organ differentiati on They exhibit an organ system level of organizati on. The head is well developed and bears the sensory organs and brain. exhibits organ system grade of organisatio n. Bilaterally symmetrica l. bilaterally symmetric . bilateral symmetry. The larval forms show bilateral symmetry and adult forms show radial symmetry. Has a pair of kidneys Symmetry -radial symmetry or none Radial symmetry bilateral symmetry Bilaterally symmetrical- Bilaterally symmetrica l. Characteristic feature generally marine aquatic organisms, with a few freshwater species. aquatic; majority marine Their body is dorsoventrally flattened. Most are freeliving, some sessile, very few parasitic characteriz ed by having a soft body, muscular foot, and (most often) a protective shell; The body is segmented which is the most distinguishi ng feature of annelids. The body is cylindrical or thread like with elongated, slender worm-like appearanc e and tapering at both ends. These are exclusivel y marine animals. Coelom/type no true coelom hece called as Acoelomates Digestive system type Circulatory system type No Coelom because they are diploblastic Acoelomate pseudocoelom coelomate coelomate not considered to be a true coelom. not coelom. considered to be a true coelom. intracellular digestion Sac-like gut (gastrovascul ar cavity, incomplete digestive tract) The digestive system is incomplete or absent. digestive system (has stomach (stores food)) Body possesses a through gut with mouth and anus. The digestive system is complete and developed. all digestion in gut or lining. The digestive tract is complete with the mouth and anus at opposite ends of the body. do not have a true circulatory system do not have respiratory or There is no circulatory system and gas Has an closed open circulatory circulatory system system with a heart Lack Circulatory System The body is uniquely shaped. It can star like, elongated or spherical. simple digestive system with a mouth, stomachs, intestinean d anus. have no have no open circulatory circulatory circulatory or or system circulatory systems. Nervous system do not have a nervous system. Nerve net, non polarized and an aorta. central nervous system (CNS), primitive nervous system Has a nervous system with a circumoesophagal ring, ganglia and paired nerve chords. respiratory respiratory systems systems Well developed nervous system The nervous system consists of a nervering that encircles the oesophagu s They have a welldeveloped central nervous system. The brain is absent but a nervous system is present with a nerve ring and radial nerve cords. Complete the following table, which compares the different types of flatworms Description Free-living flat worms Flukes Tapeworms Flatworms are soft-bodied invertebrates. This article provides an insight about the various types of flatworms and their life cycles. Flukes have complex life cycles, and they live within one or more hosts. Tapeworms are the intestinal worms. Flatworms are members of the phylum Platyhelminthes. There are more than 20,000 known species of flatworms. They are characterized by a welldeveloped digestive system with mouth at the anterior end and one or more suckers surrounding the mouth. Suckers are used to remain attached to the internal body surface of the host. They can be found in freshwater, marine, or damp terrestrial environment. Most flatworms are Schistosoma (blood flukes) free-living, however, some are spends some part of its life in parasites. Parasites live in the snails. host body and can be harmful to When humans wade in the the host. water containing snails, they get Flatworms have bilaterallyinfected. symmetrical flat bodies. They are A larva of a Schistosoma invades ribbon-shaped and are flattened the blood vessels of humans. dorsoventrally. Its eggs are passed through There are four major classes of human feces into water and the flatworms such as Cestoda snail is infected. (tapeworms), Turbellaria (planarians), Trematoda (flukes), and Monogenea. They live in the intestinal tract of many species, including dogs, cats, and even human beings. Tapeworms have segmented bodies and each segment is known as proglottid. Each proglottid is a reproductive organ. Tapeworms do not have a well-developed digestive system. They can grow very long. They remain attached to the intestine of the host using the hooks and suckers present on the head. Complete the following table, which compares the three major groups of annelids: Description Earthworms Polychaetes Leeches Each segment on an earthworm’s body has a number of bristly hairs, called setae These hairs provide some grip to help the earthworm move through the soil. The body of free-moving polychaetes of a head, or prostomium, which may bear two or more eyes; a preoral segment, with such appendages as antennae, tentacles, and palpi (fleshy sensory projections); a trunk divisible into distinct segments; and a tail, or pygidium, which may bear anal cirri (fleshy projections) or plaques and a terminal anus. Leeches have 34 segments, and elongation occurs by the subdivision of these segments. An earthworm has a streamlined body with no antennae or fins or arms or legs! This streamlined shape is an adaptation to living in narrow burrows underground and the need to move easily through the soil. An earthworm has circular muscles that surround each body segment. It also has longitudinal muscles that run the length of its body. These two groups of muscles work together to help the earthworm move. In order to get food into its mouth, an earthworm pushes its pharynx out of its mouth to grasp hold of its food. It then pulls the Each body segment following the second segment (peristome) usually has paired parapodia; i.e., fleshy, lateral outgrowths used in feeding, locomotion, or breathing. The parapodia, generally prominent in free-moving polychaetes, bear bundles of setae, which can be extended, and aciculae (needlelike structures), which are used for support. Leeches have a small sucker at the anterior end and a large sucker at the posterior end. A clitellum is present in the midregion during the reproductive period. The poorly developed eyes are paired structures at the anterior end. Setae are absent. food back into its mouth and wets Complete the following table, which compares the three major groups of arthropods: Description Chelicerates Millipedes/centipedes Crustaceans Chelicerata is a division within the Arthropoda, containing animals such as spiders, scorpions, harvestmen, mites and ticks. They are both invertebrates (without backbones) and belong to the largest phylum in the Animal Kingdom which also includes insects, spiders, crabs, lobsters, etc. This is a very diverse class. Its members display much variation in the tagmata and the appendages. There are about 30,000 species of Crustacea. Most are aquatic, the majority of which are marine. Crustaceans includes lobsters, crabs, crayfish, shrimp, barnacles, and several less familiar forms. One of the latter is the Isopoda, the sowbugs and pillbugs or rolypolys. Most people will likely Like all arthropods, they have a segmented body and segmented limbs and a thick chitinous cuticle called an exoskeleton. Chelicerates have two body segments; a cephalothorax and an abdomen. They both have one pair of antennae, many pairs of legs, and breathe through little holes or spiracles on the sides of their bodies. They have no antennae, but have six pairs of appendages. The most anterior appendages are called the chelicerae and are normally modified into pincers or fangs. The following pair, the pedipalps, are also commonly modified. The posterior four pairs of appendages are normally used for walking. Other than the marine horseshoe crabs, the Chelicerata are found primarily in terrestrial environments worldwide. Around 8,000 described species are found in Australia, with approximately 80,000 recognised species worldwide. The only class within Chelicerata which is not entirely marine is the Arachnida. They both have segmented bodies, poor vision, external skeletons and jointed legs. They grow by mounting or shedding their external skeletons and, when young, grow new segments and legs each time they moult. They are both found throughout the world, but are most abundant in the tropics. They require a moist environment and are most active at night. Millipedes have short antennae and move in slow waves, burrowing and eating their way through moist leaf clutter, fungi, and decayed plant material on the ground. As they plow through the soil, munching on dead plants and other vegetation, they aerate and enrich the soil, much like earthworms. encounter only two orders, the Orders Decapoda and Isopoda. Most isopods are marine, living in seaweed and under stones in the water. There are a few freshwater forms. The only Crustacea to invade the land are the isopods However, they have not severed all ties with the aquatic habitat for they are only found in places of high moisture. This includes places such as leaf litter and soil and beneath bark and stones. A few are occasionally pests of cultivated plants, but they usually feed on organic debris. Those that can roll into a ball are called pillbugs or roly-polys; those that can not form a ball are the sowbugs.
