Symmetry As previously stated sponges are asymetrical – this means that in whatever plane you cut them their bodies will NOT be equal Jelly fish (Cnidaria) and star fish (Echinoderms) show radial symmetry (like spokes on a wheel) this means that you can cut the body in any plane and have equal sides Higher animals show bilateral symmetry 0 this means that the body can be cut in only one plane and have equal left and right sides Animals Can Also Be Arranged by the Arrangement of Their Embryonic Cell Layers Embryonic (Germinal) Layers Animals whose cells are arranged into two embryonic layers, an outer ectoderm and an inner endoderm are called diploblastic Often an undifferentiated layer of cells is found between these two layers and is called the mesoglia This type of arrangement is found in cnidarians Embryonic (Germinal) Layers Animals that have a third embryonic layer located between the ectoderm and the mesoderm are called triploblastic This layer of tissue is called the mesoderm Platyhelminthes to chordates are all triploblastic What Becomes of these Layers? The Endoderm forms the stomach, intestines, lungs, pancreas, bladder, trachea and thyroid gland The Mesoderm forms the muscle, cartilage, urinary tract (not including bladder), heat, spleen, dermis and notochord The Ectoderm forms the hiair, nails, lens of the eye, sweat and sebacious glands, cornea, and the enamel of the teeth The Animal Kingdom – Pt-2 Classification and Organization Dr. Jim Whitfield Coelom The presence or absence of a cavity between the body wall and the gut wall is very important in classification Coelom The presence or absence of a cavity between the body wall and the gut wall is very important in classification The body cavity id called the COELOM Coelom The presence or absence of a cavity between the body wall and the gut wall is very important in classification The body cavity id called the COELOM Animals with a body cavity are called COELOMATES Coelom The presence or absence of a cavity between the body wall and the gut wall is very important in classification The body cavity is lined by mesoderm and called the COELOM Animals with a body cavity are called COELOMATES These include annelids, molluscs, arthopods, echinoderms, and chordates Coelom In some animals the mesoderm is scattered in pouches throughout the endoderm and ectoderm. Coelom In some animals the mesoderm is scattered in pouches throughout the endoderm and ectoderm. This type of body cavity is called a pseudocoelom Animals with this type of body are called pseudocoelomates Examples of this are the Aschelminthes (formally part of the platyhelminthes) Coelom Animals in which the body cavity is completely absent are called ACOELOMATES Coelom Animals in which the body cavity is completely absent are called ACOELOMATES Examples are Platyhelminthes Segmentation In some animals such as earthworms the body is divided both internally and externally into segments. Many of these segments have repeating organs this pattern of organization is called METAMERISM Notochord The notochord is derived from mesoderm. It forms on the dorsal side of the organism (Back) Animals with a notochord are called chordates Notochord forming in A chick embryo SUMMARY OF ORGANIZATION Phylum - Porifera The porifera are marine, asymmetrical animals commonly known as sponges Phylum - Porifera The porifera are marine, asymmetrical animals commonly known as sponges Sponges have a water transport or canal system. Water enters through tiny pores called ostia in the body wall and enter into the spongocoel, or central cavity, it finally exits though the osculum. Phylum - Porifera The porifera are marine, asymmetrical animals commonly known as sponges Sponges have a water transport or canal system. Water enters through tiny pores called ostia in the body wall and enter into the spongocoel, or central cavity, it finally exits though the osculum. This pathway is important in food gathering, repiratory exchange and removal of waste Phylum - Porifera Choanocytes (Collar cells) are specialized cells which contain a central flagellum which beats in unison help move the water and food through the spongocoel Digestion is intracellular The body is supported by a skeleton made up of spicules or spongin fibers. These also serve to deter predators Spicules are composed of calcium carbonate and spongin is composed of modified collagen secreted by sponogcytes Phylum - Porifera Sponges are hermaphrodites – The sexes are not separate Sponges reproduce asexually via fragmentation and sexually via the formation of gametes (egg and sperm) Fertilization occurs internally Sponges have a larval stage morphologically distinct from the adult stage Phylum – Cnidaria Coelenterata Cnidarians are aquatic, sessile or free swimming, radial symmetrical animals The name is derived from specialized cells called cnidocytes which contain stinging capsules called nematocytes Phylum – Cnidaria Coelenterata Cnidarians are diploblastic and exhibit tissue level of organization Cnidarians have a central gastro-vascular cavity with a single opening called a hypostome. The hypostome is surrounded by tentacles to help bring in food Some cnidarians (corals) have a skeleton composed of calcium carbonate Phylum – Cnidaria Coelenterata Cnidarians have two body types called the polyp and the medusa The polyp is sessile and the medusa is free swimming. Cnidarians exhibit alternation of generations. This means that the polyps produce the medusa asexually produce polyps sexually Phylum – Ctenophora Coelenterata Ctenophora are marine, radial symmetrical diploblastic organisms exhibiting tissue level of organization. They are often referred to as sea walnuts or comb jellies The body contains external rows of comb plates that help with locomotion Phylum – Ctenophora Coelenterata Ctenophora exhibit bioluminescence (the ability to emit light) All reproduction is sexual with external fertilization Ctenophora Phylum - Platyhelminthes Platyhelminthes or flatworms are bilaterally symmetrical, triploblastic, acoelomates that exhibit tissue level of organization Most are endoparasites (many found in humans) Many use hooks and suckers to absorb nutrients directly from the host Specialized cells called flame cells help with osmoregulation and excretion Phylum - Platyhelminthes Platyhelminthes are hermaphrodites with internal fertilization and development Many members of the phlya (such as planaria) show high degrees of regeneration Tapeworms Flukes Planaria Phylum – Aschelminthes Nematodes Nematodes are roundworms (refers to the shape of their body in cross section) Nematodes may be free living or parasitic, aquatic or terrestrial Nematodes exhibit organ level organization, they have bilateral symmetry, with a triploblastic body They are pseudocoelomates with a complete digestive tract and a muscular pharynx that pushes food into the esphagus Phylum – Aschelminthes Nematodes Waste is removed through excretory pores in the body Sexes are separate (Dioecious) with the females generally being larger Fertilization is internal and development may be direct or indirect Phylum – Aschelminthes Nematodes Over 25,000 species have been described Examples include: Hookworms, whipworms, pinworms, dirophilaria (heart worms) and trichinella Trichinella is the worm that causes trichinosis Phylum - Annelida Annelids are fairly complex Annelids may be marine or terrestrial, they are mostly free living (leeches are an exception) They are triploblastic, coelomates with bilateral symmetry and and organ level organization. There body surfaces are distinctly divided into segments or metameres Phylum - Annelida Alternating circular and longitudinal muscles help with locomotion – This is an example of a hydrostatic skeleton Phylum - Annelida Aquatic annelids have specialized appendages called parapodia to help with swimming Annelids have a closed circulatory system Annelids have nephridia. Nephridia come in pairs and act similarly to the kidney. They are important in osmoregulation and waste removal Annelids have a primitive brain called a ganglia that attaches to the ventral nerve among other things it can detect touch and temperature Phylum - Annelida Annelids may be monoecious or dioecious Reproduction is sexual