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Invertebrates II Phylum: Nemertea The ribbon or proboscis worms exhibit an acoelomate body plan but have a fluid sac that some suggest may be an early coelom. Alimentary canal, closed circulatory system and the fluid sac mentioned above. Phyla: Nematoda Unsegmented, round with tapered ends Pseudocoelom Complete alimentary canal No Circulatory System Dorsal and Ventral Nerve Cord Longitudinal muscles only Cuticle decomposers, agricultural pests, parasites Cooperation of Muscles and Skeletons Muscles always contract Muscles attached in antagonistic pairs Skeletal Muscles Muscles are made up of muscle fibers Fibers are made up of myofibrils Myofibrils are made up of myofilaments – thin filaments (actin) – thick filaments (myosin) Sliding Filament Model Sacromeres (basic functioning unit) – Z lines (border of sacromeres) – H zone (center of sacromere) – I band (only thin filaments) – A band (length of thick filaments) Sliding Filament Model During contraction, thin and thick filaments slide past each other – I band and H zone decreases in size Caused by myosin head creating cross bridge with actin fiber and then moves by using ATP Muscle Control Tropomyosin blocks myosin binding sites Calcium ions allow cross bridges to form Muscle Fibers Fast Muscle Fibers – rapid, powerful contractions – flight muscle Slow Muscle Fibers – sustain, long contractions – adductor muscles Invertebrate Muscles Flight muscles in insects are capable of independent contractions – wings beat faster than action potentials Clam muscles contain paramyosin that allows them to remain contracted with little energy Nematodes only have longitudinal muscle that gives them their characteristic movements Ancylostoma Hookworm (burrows into skin and moves to intestine) Enterobius Pinworm (pick up eggs from anus or dust with eggs) Ascaris Human in food) roundworm (pick up eggs Trichinella Trichina worm (pick up from infected muscle in pork) Wuchereria Causes elephantiasis blocks lymph channels pick up from mosquitoes Phylum: Arthropoda Hard exoskeleton, segmented Segments carry paired appendages Open circulatory system Alimentary Canal Complex Muscular system Nervous system similar to annelids Malphigian Tubules for excretion Skin, Gills, Trachaea or Book lungs for respiration Contains two-thirds of all identified species Arthropod Diversity Versatile exoskeleton Segmentation and appendages Tracheae Highly developed sense organs Complex behavior patterns Metamorphosis Invertebrate Structures Malpighian Tubules Open into the digestive tract Osmoregulation and excretion Insects and terrestrial arthropods Conditions for Respiratory Surfaces Large Thin Moist surface area Aquatic vs. Terrestrial Less than 1% oxygen Oxygen amounts decrease as the temperature increases Aquatic animals use large amounts of energy to obtain oxygen (20%) About 21% oxygen Developed invaginations to increase surface area and decrease evaporation Terrestrial animals may use only 1% 2% of its energy to obtain oxygen Respiratory Surfaces Cutaneous Respiration Gills Tracheal Lungs Systems Cutaneous Respiration Direct diffusion of gases between the organism and the environment Found in Porifera, Cnidarians, Platyhelminthes, nematodes, and some annelids Supplements other organisms Gills Found in echino-derms, mollusks, annelids, arthropods, some vertebrates Tracheal Systems Found in arthropods Tracheae – open tubes Spiracles – openings Tracheoles – contact with cells Muscle – increase amount of Carbon Dioxide removed Tracheal Systems Diffusion Lungs Found in invertebrates Gas moved primarily by diffusion – may be increased by body movement Modifications – snails - cavity with gill modified into lung – scorpions and spiders - invaginations of the abdomen (Book Lungs) Sensory Receptors Mechanoreceptors Pain Receptors Thermoreceptors Chemoreceptors Electromagnetic Receptors Sensory Receptors Mechanoreceptors Pain Receptors Thermoreceptors Sensory Receptors Chemoreceptors Evolution of the Eye Complex eyes have developed many times Evolution of the Eye All light-sensitive organs rely on photoreceptor systems employing a family of proteins called opsins. Further, the genetic toolkit for positioning eyes is common to all animals: the PAX6 gene controls where the eye develops in organisms ranging Photoreceptors Eye cups (ocelli) - light detection Genetic basis that started as a light detector 600 mya During the Cambrian explosion around 540 mya two types of eyes arose Photoreceptors Compound Eyes made up of ommatidia that helps detect movement Arthropod Classification Subphylum: Trilobita Subphylum: Cheliceriformes – Class: Merostomata (Horseshoe crabs) – Class: Pycnogonida – Class: Arachnida (Scorpions, Spiders, Ticks, Mites) Arthropod Classification Subphylum: Crustacea – Class: Crustacea (Lobster, Crabs, Shrimp) Subphylum: Myriapoda – Class: Chilopoda (Centipedes) – Class: Diplopoda (Millipedes) – Class: Insecta (Insects) Subphylum: Trilobita All extinct (Permian era - 250 mya) Segmented without specialization Paired appendages Subphylum: Cheliceriformes Six pairs of appendages – one pair of chelicerae – one pair of pedipalps (not in horseshoe crabs) – four pair of walking legs No mandibles No antennae Class: Merostomata Six pairs of appendages – one pair of chelicerae – five pair of walking legs Unchanged since the triassic period Shallow coastal waters Larvae similar to trilobites Class: Pyconogonida Called Sea spiders (not true spider) May have extra legs (duplicate segments) Polar oceans Class: Arachnida Class: Arachnida Scorpions are the first terrestrial invertebrates – pedipalps modified as pinchers – tail modified with stinger Ticks and Mites are parasitic Spiders contain modified chelicerae – used as fangs to inject poison – produce silk used for webs, eggs, escape, courtship Subphylum: Crustacea Subphylum: Crustacea Contain two pair of antennae Each appendage is biramous (two main branches) Mandibles Body of two or three parts Mostly marine Subphylum: Myriapoda Subphylum: Myriapoda Contain one pair of antennae Each appendage is uniramous (one main branch) Mandibles Classes: Chilopoda & Diplopoda Chilopoda – Centipedes – one pair of jointed legs per segment – poison claws – predators Diplopoda – Millipedes – two pair of jointed legs per segment (fused) – herbivores Class: Insecta Most diverse of all arthropods May have been the cause of angiosperm diversity Metamorphosis – complete – incomplete Coleoptera – Beetles Two pairs of wings, one thick, the other membranous Chewing mouth parts Diptera – True Flies One pair of clear wings Sucking mouth parts Lepidoptera – Butterflies & Moths Two pairs of wings with scales Long proboscis Hemiptera – True Bugs Two pairs of wings, one half wing (thick in front, membranous in back) and the other membranous Piercing or sucking mouthparts Homoptera – Cidadas, Aphids Wings held roof-like over body Piercing – sucking mouth parts Hymenoptera – Ants, Bees, Wasps Two pairs of membranous wings Thin waist Odonata – Dragonflies Long, narrow membranous wings Long, slender body Orthoptera Large Hind legs for jumping Two pairs of wings (one leathery, one membranous) Phylum: Echinodermata Deuterostomes – radial and indeterminate cleavage – Enterocoelous – anus from blastopore Phylum: Echinodermata Secondary Radial Symmetry Water vascular system – Ambulacral groove – Madreporite All marine Water Vascular System Madreporite Stone Canal Ring Canal Radial Canal Lateral Canal Ampulla Tube Feet Classification Class: Asteroidea (Seastars) Class: Opiuroidea (Brittlestars) Class: Echinoidea (Sea Urchins, Sand Dollars) Class: Crinoidea (Sea Lilies) Class: Holothuroidea (Sea Cucumbers) Class: Asteroidea Five arms radiating from a central disc Open ambulacral groove Madreporite on the aboral side Contain pedicellariae or papulae Class: Ophiuroidea Five thin arms radiating from a central disc Closed ambulacral grooves Madreporite on the oral side No suckers on tube feet, pedicellariae or papulae Class: Echinoidea No arms but have five rows of tube feets Contain spines Closed ambulacral grooves Madreporite on the aboral side Contain pedicellariae or papulae Aristotle’s lantern Class: Crinoidea Attached to substrate with many branched arms Open ambulacral grooves No Madreporite No pedicellariae or papulae Class: Holothuroidea Soft bodied Ambulacral areas with tube feet Internal Madreporite No pedicellariae or papulae
