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Animal Taxonomy Phylum Porifera Sponges lack true tissues and organs Have 2 layers of cells Filter feeders using choanocytes, flagellated collar cells which create a water current Most sponges are hermaphrodites Cnidarians Jellyfish (medusa), corals, hydras, anemones (polyps) Radially symmetrical, have a gastrovascular cavity and a nerve net Have 2 layers of cells Carnivores that use tentacles armed with cnidocytes to capture prey Platyhelminthes Flatworms have a gastrovascular cavity and are acoelomates Planarians have light-sensitive eyespots and centralized nerve nets, found in all types of moist habitats Tapeworms and flukes are parasites that have a complex life cycle involving 2 or more hosts Annelids, Molluscs and Arthropods are protostomes Have spiral, determinate cleavage Mesoderm splits to form the coelom Mouth forms from the blasotpore Molluscs are soft-bodied animals, but most are protected by a hard shell Phylum Mollusca includes snails, slugs, oysters, octopuses and squids All molluscs have a similar body plan with three main parts: muscular foot, mantle and visceral mass Have a complete digestive tract Open circulatory system Have a siphon system to bring water in and out of their bodies and gills for gas exchange Nephridium help excrete nitrogenous wastes Cephalopods have large brains, eyes and are highly intelligent Polyplacophora (chitons) oval-shaped marine animals encased in an armor of eight dorsal plates Gastropoda (snails and slugs) Most have a single, spiraled shell, and exhibit torsion, which causes the animal’s anus and mantle to end up above its head Bivalvia (clams, oysters) have 2 shells Cephalopoda (squids, octopuses, cuttlefish, and chambered nautiluses) beak-like jaws surrounded by tentacles of their modified foot Annelids are segmented worms earthworms, polychaetes, leeches Annelids have bodies composed of a series of fused rings each with circular and longitudinal muscles which contract against fluid in the coelom so they can move (hydrostatic skeleton) Annelid characteristics Gas exchange is through their skin Closed circulatory system with multiple hearts Metanephridia excrete nitrogenous wastes through the skin Have cerebral ganglia and a dorsal nerve cord Have a true coelom Have a complete digestive system with many parts Nematodes are nonsegmented pseudocoelomates Nematodes, or roundworms, are found in most aquatic habitats, in the soil, in moist tissues of plants, and in body fluids and tissues of animals The cylindrical bodies of nematodes are covered by a tough coat called a cuticle Arthropods Have regional segmentation Different segments are specialized for different functions Jointed appendages Each is modified for: walking, feeding, sensory reception, copulation, or defense Cephalization Many sensory structures are found at the anterior end Organ systems Complete digestive system Open circulatory system with hemolymph Excretory organs are Malpighian tubules, empty nitrogenous waste into digestive tract Gas exchange through trachea with spiracles that open to the outside Pair of ventral nerve cords with several segmental ganglia; anterior ganglia are fused into a dorsal brain Gas exchange structures Feathery gills in aquatic species Tracheal systems in insects Book lungs in spiders Exoskeleton of protein and chitin Thin and flexible at joints, thick and hard at others Provides protection, points of muscle attachment, waterproofing Has to be shed for animal to grow Open circulatory system Hemolymph leaves the heart and passes into sinuses which surround tissues and organs and reenters the heart through pores with valves Classes Chelicerates spiders, scorpions, ticks, mites; named for their feeding appendages, the chelicerae Hexapoda, insects, has more species than all other forms of life combined; have several complex organ systems; many undergo metamorphosis during their lives Crustaceans, subphylum Crustacea, typically have branched appendages that are extensively specialized for feeding and locomotion Decapods are all relatively large crustaceans and include lobsters, crabs, crayfish, and shrimp Echinoderms and chordates are deuterostomes Radial, determinate cleavage Development of the coelom from folding of the archenteron Formation of the anus from the blastopore Echinoderms A thin, bumpy or spiny skin covers an endoskeleton of hard plates Have a water vascular system, a network of hydraulic canals branching into tube feet that function in locomotion, feeding, and gas exchange Chordates and subphylum vertebrata Characters of Chordates Chordataes are bilaterial deuterostomes Four key characters of chordates: Notochord Dorsal, hollow nerve cord Pharyngeal slits or clefts Muscular, post-anal tail Some species have some of these traits only during embryonic development Notochord The notochord is a longitudinal, flexible rod between the digestive tube and nerve cord It provides skeletal support throughout most of the length of a chordate; most vertebrates develop a jointed skeleton Dorsal, Hollow Nerve Cord The nerve cord of a chordate embryo develops from a plate of ectoderm that rolls into a tube dorsal to the notochord The nerve cord develops into the central nervous system: the brain and the spinal cord Pharyngeal Slits or Clefts In most chordates, grooves in the pharynx called pharyngeal clefts develop into slits that open to the outside of the body Functions of pharyngeal slits: Suspension-feeding structures in many invertebrate chordates Gas exchange in aquatic vertebrates Develop into parts of the ear, head, and neck in terrestrial vertebrates Muscular, Post-Anal Tail Chordates have a tail posterior to the anus In many species, the tail is lost during embryonic development; if not it can often be used for movement Urochordates and cephalochordates Although invertebrates, are more closely related to vertebrates Tunicates and lancelets: marine filter feeders Jawless fish Hagfishes are jawless marine craniates that have a skull and axial rod of cartilage along their back Secrete massive quantities of slime from glands in their skin Scavengers Derived Characters of Vertebrates Vertebrates have the following derived characters: Vertebrae enclosing a spinal cord An elaborate skull Fin rays, in aquatic forms Cephalaspidomorphi Lampreys They are jawless aquatic vertebrate with have cartilaginous segments around the notochord and part of the nerve cord Parasites of fish Chondrichthys Sharks, Rays, skates Members of class Chondrichthyes have a skeleton composed primarily of cartilage Osteichthies Have a bony endoskeleton Fishes control their buoyancy with an air sac known as a swim bladder Fishes breathe by drawing water over gills in chambers covered by a bony flap called the operculum Have countercurrent flow of water and blood in their gills Have a 2 chambered heart Marine fish excrete salt from their gills and make a small amount of urine Freshwater fish excrete large amounts of dilute urine to maintain osmoregulation Lateral line allows them to feel vibrations in the water Derived Characters of Tetrapods Tetrapods have some specific adaptations: Four limbs and feet with digits Ears for detecting airborne sounds Amphibians: Frogs, salamanders, caecilians Most amphibians have moist skin that complements the lungs in gas exchange Amphibian means “two lives,” referring to the metamorphosis of an aquatic larva into a terrestrial adult; need water for reproduction Have a 3 chambered heart Derived Characters of Amniotes Amniotes produce the amniotic egg, which contains membranes that protect the embryo The extraembryonic membranes have various functions Have relatively impermeable skin and can use the muscles of the rib cage to ventilate the lungs Reptiles Tuataras, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs Reptiles have scales They lay shelled eggs on land Most are ectothermic Have a 3 chambered heart Birds Birds are brachiosaurs, but almost every feature of their reptilian anatomy has been modified for adaptation to flight A bird’s most obvious adaptations for flight are its wings and feathers Bones are light-weight and hollow Have a 4 chambered heart and one way flow of oxygen through their lungs Sea birds excrete salt through salt glands in their nostrils Mammals are amniotes that have hair and produce milk Mammary glands, which produce milk, are a distinctively mammalian character Hair is another mammalian characteristic Mammals generally have a larger brain than other vertebrates of equivalent size Have a 4 chambered heart Monotremes Monotremes are a small group of egg-laying mammals consisting of echidnas and the platypus Marsupials Marsupials include opossums, kangaroos, and koalas A marsupial is born very early in its development It completes its embryonic development while nursing in a maternal pouch called a marsupium Eutherians (Placental Mammals) Compared with marsupials, eutherians have a longer period of pregnancy Young eutherians complete their embryonic development within a uterus, joined to the mother by the placenta Derived Characters of Primates Most primates have hands and feet adapted for grasping Other derived characters of primates: A large brain and short jaws Forward-looking eyes close together on the face, providing depth perception Well-developed parental care and complex social behavior A fully opposable thumb Living Primates There are three main groups of living primates: Lemurs, lorises, and pottos Tarsiers Anthropoids (monkeys and apes)