Animal Kingdom Invertebrates Members of the domain Eukarya

Animal Kingdom Invertebrates • Members of the domain Eukarya, kingdom Animalia • Heterotrophic by ingestion • Most often move by muscle fiber contraction • Multicellular with specialized cells that form tissues & organs • Life cycle where adult is diploid • Usually undergo sexual reproduction that produces a developing embryo

Animals • Believed to have evolved from protistan ancestor 700 million years ago • Most animal phyla are invertebrates – Lack endoskeleton of bone or cartilage – Lack a backbone or vertebral column • Phylum Chordata is the only phylum with a endoskeleton of bone or cartilage – Considered vertebrates – Vertebral column replaces notochord

Level of Organization • • Three levels of organization in animal kingdom: cellular, tissue, & organ levels. There are 3 primary germ layers that develop into specialized tissues that make up organism: 1. Endoderm 2. Mesoderm 3. Ectoderm

Type of Body Plan • 1. There are 2 types of body plans in animal kingdom: Sac plan – – – 2. Incomplete digestive system Has a single opening where food enters & wastes exit Ex. Hydra Tube-within-a-tube plan – – – Inner tube is digestive tract Outer tube is body wall Has two separate openings Food enters in one opening with wastes exit a different hole Ex. Humans, crayfish

Type of Symmetry • Asymmetrical: no symmetry – Ex. Some sponges • Radial symmetry: animal is organized circularly like a wheel. – Ex. Cnidarians • Bilateral symmetry: definite right & left halves – Longitudinal cut produces mirror images – Ex. Humans • Cephalization= sensory organs & brain localized at anterior end (head)

Type of Body Cavity • Coelom: body cavity that contains animal’s internal organs Ex. Earthworms, humans • Acoelomate: no body cavity Ex. Flatworms • Pseudocoelom: body cavity that is partially lined with mesoderm Ex. Roundworms

Body Cavities Cont. • The importance of body cavities include: – Provide a space in which internal organs can be placed – Allow body systems to work efficiently because they are not compressed – Allow room for internal organs to develop & expand – May contain fluids involved in internal transport, or carry waste or food from one part of the body to another

Two Major Groups of Coelomates • Based on embryonic development • If first embryonic opening becomes a mouth the animal is a protostome Ex. Clams, earthworms, crayfish • If second opening becomes a mouth the animal is a deuterostome Ex. Starfish, humans

Segmentation • Repetition of body parts along the length of the body • Animals can be segmented or nonsegmented • Leads to specialization of parts

Sponges • • Phylum Porifera Aquatic, mostly marine Vary in size, shape, color Multicellular but lack organized tissues Have cellular level of organization Outer layer of cells made of flattened epidermal cells (contractile fibers) Middle layer of cells is semifluid matrix (ameboid cells) Inner layer has flagellated cells called collar cells

Sponges cont. • The flagella on collar cells produce water currents that flow through pores into central cavity out the osculum • Sessile filter feeders (digest food within cells) • Pores in the walls and microvilli making up part of the collar cells strain food from water • Food passes from collar cells food vacuoles ameboid cells to all cells • Reproduce asexually by any of these methods: fragmentation, regeneration, gemmule formation, or budding

Sexual Reproduction in Sponges • Ameboid cells produce the sex cells and spicules (small needle-shaped structures) • Sperm are released through osculum • A different sponge will draw in the sperm through its pores where it will fertilize eggs within the body • Most sponges are hermaphoditic (contain male & female sex organs) • Sponges do NOT usually self-fertilize • After fertilization, zygote becomes flagellated larva that swim to new location

Cnidarians: True Tissues • Phylum Cnidaria • Multicellular, tubular, or bell-shaped animals found in shallow coastal waters • Radially symmetrical • Have tissue level of organization • Cnidocytes are specialized stinging cells • Nematocysts threadlike fibers found in cnidocytes that are used to capture or sting prey

Cnidarians cont. • Examples: sea anemone, jellyfish, Hydra, corals • 1. 2. Two basic body forms: Polyp= sessile stage Medusa= sexual, motile stage; has a lot of mesoglea (jellylike material); produces sperm & egg • Alternates between poly & medusa stage throughout life cycle • Zygote develops into ciliated larva capable of dispersal

Hydra • Class Hydrozoa • Freshwater cnidarian found attached to underwater plants & rocks • Has a sac body plan (one opening serves as mouth/anus) • Only have the poly stage (NO medusa stage) • Body composed of: – Epidermis: outer most tissue layer – Mesoglea: middle tissue layer – Gastrodermis: inner tissue layer made up (of gastrodermal cells) • Contain circular & longitudinal muscle fibers – Body can contract or extend – Can use tentacles that ring the mouth to reach out & grasp prey • Contain nerve cells & a nerve net (primitive brain)

Hydra cont. • Gastrovascular cavity (found in all cnidarians) – Carries on digestion using food vacuoles in gastrodermal cells – Acts as circulatory system by distributing food and gases • They can reproduce sexually or asexually – Sexual reproduction involves an ovary or a testis developing in the body wall – Asexual reproduction involves regeneration and budding bud

Flatworms: Bilateral Symmetry • Phylum Platyhelminthes • Have three germ layers (endoderm, mesoderm, ectoderm) • Acoelomate= no coelom (body cavity) • Have muscles and excretory, reproductive and digestive systems • Lack respiratory and circulatory systems – Body is flat and thin – Diffusion is used to pass oxygen and other substances cell to cell

Planarians: Flatworms • Mostly freshwater found in lakes, ponds, streams, and springs • Feed on small living or dead organisms (worms) • Excretory system consisting network of interconnecting canals • Flame cells have cilia that beat to keep water moving to excretory pores

Planarians cont. • Have ladder-like nervous system – Small anterior brain with two lateral nerve cords joined by cross branches – Have cephalization (brain localized in anterior head) – Have light sensitive eyespots • Have chemosensitive organs located on auricles • Have three muscle layers that allow varied movement • Possess a ciliated epidermis that enables gliding along a mucus film

Planarian cont. • Can reproduce both sexually and asexually • Hermaphroditic • Can cross fertilize where the penis of one worm is inserted into the genital pore of another – Exchange of sperm takes place – Fertilized eggs hatch in 2 -3 weeks • Asexual reproduction occurs by regeneration

Parasitic Flatworms • There are 2 classes: 1) tapeworms (Cestoda) & 2) flukes (Trematoda) • Tapeworms as adults are endoparasites to several vertebrates • Have tough integument (body covering) to protect from host’s harsh digestive system

Parasitic Flatworms • Have well-developed anterior region called the scolex – Scolex has hooks for attachment to intestinal wall of host – Have suckers for feeding

Parasitic Flatworms • Proglottids= series of reproductive units with a full set of male & female sex organs • Each proglottid fertilizes its own eggs – Immature proglottids located behind scolex – Mature proglottids are farther away

Flukes • Endoparasite of several vertebrates • Nonciliated integument (skin) • Oral suckers found at anterior end – Surrounded by sensory papillae – Used to attach to host • Nervous & digestive systems are reduced • Poorly developed sense organs • Most are hermaphroditic

Roundworms: Pseudocoelomates • Phylum Nematoda • Have tube-within-a-tube body plan (have mouth & anus) • Have a fluid-filled body cavity called pseudocoelom – Provides space for the development of organs – Substitutes for circulatory system – Provides type of skeleton called a hydrostatic skeleton • Hydrostatic skeleton: fluid -filled interior that supports muscle contraction • Bilaterally symmetrical • Colorless, non-segmented • Live in freshwater, marine, & soil habitats • Can be free-living or parasitic

Ascaris: roundworm • Females are larger than males • Move by whiplike motions • Most commonly parasites of humans & pigs • Female can produce over 200, 000 eggs daily • Eggs are eliminated in host feces • Eggs enter host by uncooked veggies, dirty fingers or ingested fecal material • Eggs hatch in intestines into juvenile worms

Other Roundworms • Trichinosis is an infection caused by Trichinella spiralis – Caused by eating undercooked pork that contains encysted larvae – Adult female burrows in intestinal wall & deposits larva – larva move to bloodstream & encyst in skeletal muscles • Symptoms include digestive problems, fatigue, fever, aching joints, muscle pain

Molluscs: Coelomates • • Phylum Mollusca (make up second largest phylum) Bilateral symmetry, three germ layers, organ level of organization • Tube-within-a-tube body plan • Three distinct parts all molluscs have: 1. Visceral mass= soft-bodied part that contains internal organs (digestive tract, paired kidneys, reproductive parts) 2. Foot= strong muscular portion used for locomotion 3. Mantle= membranous or muscular covering the envelops the visceral mass; may secrete a shell (exoskeleton) • Often have a rasping, tongue-like radula which has teeth and is used to obtain food

Gastropods: Class Gastropoda • Nudibranchs (sea slugs), conchs, & snails • Move by contracting muscular foot • May be herbivores or carnivores • Terrestrial, freshwater, or marine habitats • All but nudibranchs have a univalve coiled shell • May have gills (aquatic) or a mantle with blood vessels that acts as a lung • Land snails are hermaphoditic • Each snail inserts its penis into each other’s vagina • Fertilized eggs are deposited externally without swimming larvae

Bivalves: Class Bivalvia • Clams, mussels, scallops, & oysters • Shells have 2 parts • Shells are secreted by the mantle – Composed of protein, calcium carbonate, mother-of-pearl – Pearls form when foreign matter is trapped between mantle & shell • Adductor muscles hold shells together • Gills are used for gas exchange

Bivalves: Class Bivalvia • Clams are filter feeders • Has a 2 chambered heart with a pericardial cavity • Has an open circulatory system because blood is not contained in blood vessels after it leaves heart • Inside of organs, blood flows through sinuses (spaces) • Clams lack cephalization • Move by extending muscular foot & pulling body after it • Digestive system includes a mouth, esophagus, stomach and intestines, ending in an anus • Kidneys remove liquid wastes • Sexes are separate • Clams have a larval stage • Marine clams have trochophore larva

Annelids: Segmented Worms • Phylum Annelida that includes marine worms, leeches, & earthworms • Most are marine • Segments are divided by septa • Well-developed coelom that is fluid-filled and acts as a hydrostatic skeleton – Permits each body segment to move independently – Locomotion involves contraction & expansion of each segment • Tube-within-a-tube body plan with specialized digestive tract – Includes a pharynx, esophagus, crop, gizzard, intestine, & accessory glands

Annelids: Segmented Worms cont. • Have a closed circulatory system with blood vessels that run entire length of body & branch to every segment • Nervous system consists of a brain connected to a ventral solid nerve cord • Ganglia occur in each segment • Excretory system consists of paired nephridia in most segments – Nephridium: tubule that collects waste material and excretes it through opening in body wall • Setae are bristles that anchor the worm & help it move

Annelids: Segmented Worms cont. • Earthworms are hermaphroditic – Male organs are testes, seminal vesicles, sperm ducts – Female organs are ovaries, oviducts, & seminal receptacles • When mating, 2 worms lie parallel facing each other in opposite directions – Clitellum secretes mucus to prevent sperm from drying out as it passes between 2 worms – After worm separate, clitellum produces a slime tube – Muscular contractions move eggs & sperm together and fertilization to occurs – Slime tube protects developing worms – There is no larval stage

Arthropods: Jointed Appendages • Phylum Arthropoda that is divided into 3 subphyla 1. Subphylum Crustacea: barnacles, shrimps, lobsters, & crabs (mostly marine) 2. Subphylum Uniramia: insects like bees, ants, termites 3. Subphylum Chelicerata: arachnids such as terrestrial scorpions, spiders, ticks, mites • Have a jointed exoskeleton made of chitin – – Provides protection Attachment for muscles Locomotion Prevents drying out

Arthropods: Jointed Appendages cont. • Must molt or shed exoskeleton as they grow larger – Secretes new exoskeleton before molting • Segmented body often fused into head, thorax, and abdomen • Have specialized appendages for walking, swimming, reproducing, eating, & sensory perception • Well-developed nervous system with a brain & solid nerve cord – Head bear antennae & two types of eyes (compound & simple) – Compound eye= composed of many complete visual units that each operate independently – Lens= focuses an image on light sensitive membranes that contain photoreceptors for each unit – Vision is good at detecting movement

Crustaceans • Segmented animals with rigid exoskeleton • Have open circulatory system • Usually have a pair of compound eyes with five pairs of appendages • Green glands excrete metabolic wastes through a duct to outside of body • Male crustacean deposits sperm in female which holds on to it until she lays eggs • After eggs leave ovary, they stick to swimmerets until they hatch • Blood is blue due to hemocyanin which carries oxygen

Arachnids: Class Arachnida • Subphylum Chelicerata • Most numerous are the spiders • Bodies are divided into 2 parts: the cephalothorax & the abdomen • Have 1 pair of chelicerae, 1 pair of pedipalps, and four pairs of walking legs • Use chelicerae as fangs to inject poison to kill prey • All spiders have venom, but not all are poisonous to humans • Silk is released through spinnerets to make webs or to contain food • Females can use silk to hold eggs

Arachnids: Class Arachnida • Spiders use book lungs for respiration – Consist of folded membranes that look like pages in a book – Folding increases surface area for gas exchange • Spiders reproduce sexually • Male sperm cells are held in seminal receptacle in female • When it is time to lay eggs, sperm is released on eggs

Insects • • 1. 2. 3. 4. • • Subphylum Uniramia is very numerous & diverse All insects have the following features in common: Body divided into 3 parts: head, thorax, abdomen Head bears pair of sensory antennae, pair of compound eyes, & several simple eyes Abdomen contains most of the internal organs Thorax bears 3 pairs of legs and the wings (either 1 or 2 pairs or no pairs) Excretory system consists of malpighian tubules Respiratory system begins with openings in exoskeleton called spiracles Air then enters tubules called tracheae Air is pumped via muscular contraction of body wall

Differences between arachnids & insects: 1. 2. 3. 4. Arachnids have 8 legs; insects have 6 legs Arachnids have 2 body segments; insects have 3 Insects have antennae, arachnids do not Insects have wings attached to the thorax; arachnids do not have wings • Unique to insects is that they go through developmental stages called a metamorphosis – Incomplete metamorphosis: egg nymph (small adult) adult Ex. Dragonflies, grasshoppers – • Complete metamorhosis: 4 stages egg, larva, pupa, adult Ex. Butterflies, ants Both insects and arachnids molt

Phylum Echinodermata • Echinoderms – Invertebrate animal group most closely related to chordates (that’s us) • Similar embryological development • Deuterostome with second embryonic opening forming the mouth – Marine animals that do have an endoskeleton • Consists of spine-bearing, calcium rich plates • Spines stick out through skin – Echino- (spiny) derm- (skin)

Echinoderms cont. • Most have pentamerous radial symmetry – Radial symmetry that can be broken into 5 equal parts • Larva is a free-swimming filter feeder • Examples of echinoderms: sea lilies, feather stars, brittle stars, sea cucumbers, sea stars, sea urchins • Sea stars have an aboral side or anus side (upper side) & an oral (mouth) side on underside • Have a well-developed coelom

Sea Stars cont. • Have endoskeletal plates that provide protection • Have pedicellariae that keep surface free of particles • Have skin gills used for gas exchange • Lack respiratory, excretory, & circulatory systems

Sea Stars cont. • Have tube feet – Series of small suction discs found on oral surface – Used for locomotion and food retrieval • Most are carnivorous – – – Mouth is located on underside Feeds by pushing its cardiac stomach out Stomach releases digestive enzymes on food Digestion begins outside of body Later partially digested food is brought into body • Each arm contains a pair of digestive glands & gonads (either male or female) • Nervous system consists of central nerve ring & radial nerves with light sensitive eyespot

Sea Stars cont. • Have a water vascular system with tube feet – Water enters through the madreporite on upper surface – Water then moves through the arms to the tube feet – Each foot moves by continually filling and emptying of water • Reproduction is usually sexual • Capable of asexual reproduction via regeneration – Fragment must contain part of central disc