Animal Kingdom Invertebrates

1. 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

2. 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

3. 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: • Endoderm • Mesoderm • Ectoderm

4. Type of Body Plan • There are 2 types of body plans in animal kingdom: • Sac plan • 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

5. 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)

6. 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

7. 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

8. 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

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

10. 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

11. 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

12. 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

13. 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

14. Cnidarians cont. • Examples: sea anemone, jellyfish, Hydra, corals • 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

15. 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)

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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: • Visceral mass= soft-bodied part that contains internal organs (digestive tract, paired kidneys, reproductive parts) • Foot= strong muscular portion used for locomotion • 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. Arthropods: Jointed Appendages • Phylum Arthropoda that is divided into 3 subphyla • Subphylum Crustacea: barnacles, shrimps, lobsters, & crabs (mostly marine) • Subphylum Uniramia: insects like bees, ants, termites • 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

36. 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

37. 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

38. 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

39. 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

40. Insects • 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

41. Differences between arachnids & insects: • 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

42. 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)

43. 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

44. 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

45. 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

46. 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