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Unit 3 Invertebrates The 9 Major Animal Phyla • Phylum Porifera • Phylum Cnidaria • Phylum Platyhelminthes • Phylum Nematoda • Phylum Annelida • Phylum Mollusca • Phylum Echinodermata • Phylum Arthropoda • Phylum Chordata Characteristics of Animals • • • • Multicellular Eukaryotic Cells lack cell walls Heterotrophic- are consumers…they get their energy from another food source. • Most animals have some sort of a nervous system. • Most animals use glycogen to store energy Symmetry (Pg. 684) • All animals show some sort of symmetry 1. Assymmetry – Irregular shapes – Do not move (Sessile) – Sponges 2. Radial Symmetry Can divide into equal halves using many planes. Cnidaria (stinging animals) Echinoderms (sea stars) 3. Bilateral Symmetry • Can only divide into left & right halves • Most efficient for movement – Flatworms – Roundworms – Mollusks – Segmented Worms – Chordates The 3 Germ Layers • After fertilization of the egg the new zygote begins to divide to form the new multicellular organism. • During this process of cell division (called embryogenesis), the cells of most organisms differentiate into 3 different layers. • The 3 germ layers are: ectoderm, mesoderm and endoderm Phylum Porifera (Sponges) General Characteristics Adults are sessile (attached to one spot) Asymmetrical or radial body plan Typical body form is hollow with two layers of cells (no true tissues) separated by a jelly like substance. Sponges have a “skeleton” of silicon or calcium carbonate called Spicules or of fibrous spongin Food Capture & Digestion • Water passes into the sponge through openings called ostia. • As the water is passing through the sponge, specialized flagellated cells called collar cells trap, ingest and then digest food particles. • Collar cells also create the current that pulls the water through the ostia and out through a larger opening in the top of the sponge called the osculum. Food Capture & Digestion • Special cells in the middle layer called amebocytes pick up the partly digested food from the collar cells, complete the digestion process and transport the nutrients to other parts of the sponge. Respiration • Sponges do not have any specialized organs or tissues for respiration. • As water passes through the sponge gas exchange is accomplished by diffusion. • Waste products are also excreted through diffusion. Reproduction • Asexual – Budding creates new small sponges or gemmules in some groups (A group of cells that are enclosed in a tough outer covering that develop into a sponge when conditions are favorable). • Sexual – Collar cells change into gametes. Sperm leave via the osculum and are drawn into the ostia or pores of other sponges where they enter eggs in jelly like middle layer to form zygotes. Cnidaria General Characteristics • They are radially symmetrical •Bodies are saclike with a central gastrovascular cavity with one opening. (Their mouth is their anus) •They have 2 tissue layers • Outer layer of cells - ectoderm • Inner layer - endoderm • In between these tissue layers is a noncellular jelly-like material called mesoglea. Cnidarians have no true tissues, but have a “primitive” nerve net. “A no brainer” Cnidarians have 2 body plans: Respiration & Waste Disposal •There is no system of internal transport, gas exchange or excretion; all these processes take place via diffusion Platyhelmintes (Flatworms) Gen. Characteristics • They exhibit bilateral symmetry: anterior and posterior ends are different; so are the dorsal and ventral surfaces •Exhibit some degree of cephalization •This phylum (and all remaining phyla) possesses 3 germ layers (endoderm, ectoderm, & mesoderm) • The mesoderm (middle germ layer) gives rise to muscles and various organ systems. Organ Systems of Flatworms Cells are organized into tissues Diagrams on pg. 692 of text. Digestive System • Planaria are flatworms that possess a digestive system, with a mouth, pharynx, and a branching intestine from which the nutrients are absorbed. The intestine, with only one opening, is a blind system . •Flukes and tapeworms are parasites that have no digestive system so they absorb nutrients that have already been digested from their host. Excretory System •A network of water collecting tubules adjacent to flame cells. These cells remove the wastes from the body through pores in the skin. • Parasites remove wastes via diffusion. Reproductive System • Most are capable of some form of asexual reproduction (e.g., many turbellarians reproduce by fission, many can regenerate lost body parts) • Most flatworms are hermaphroditic (have both male & female sex organs); however, they must pair with other individuals to exchange gametes. They cannot self fertilize. • Nematoda - The Roundworms • Includes roundworms, Pinworms, Filaria, Hookworms,Trichina, Ascaris General Characteristics • Bilaterally symmetrical cylindrical bodies covered with a tough cuticle. • Have all 3 germ layers. Nematodes do not have a respiratory or circulatory system; both are accomplished by diffusion • Body has 2 openings: a mouth and an anus Reproduction • Sexual reproduction only. • Fertilization occurs inside the body of the female. Fertilized eggs are covered by a thick shell. • Separate male and female worms. Mollusca General characteristics: •Bilaterally symmetrical & all have a coelom •All have mantle with shell glands that secrete calcareous epidermal spicules, shell plates, or shells. •Have large, well defined muscular foot, often with a flattened creeping sole, in squids and octopus, the foot is modified into tentacles/arms. •All have soft fleshy bodies which may be covered by a shell, etc. General Characteristics (cont.) • A well developed open circulatory system • Well developed nervous system in Cephalopods and Gastropods • All have kidneys for excretion • Only undergo sexual reproduction, separate sexes, external fertilization • Oyster Spawning • • • • Includes the Phyla: Bivalvia – Clams, etc. Gastropoda – Snails, Slugs, etc. Cephalopoda – Octopus, Squid, Nautilus • Know the characteristics of each class. Kingdom Animalia – Phylum Echinodermata Phylum Echinodermata (spiny skin) – sea stars, brittle stars, sea cucumbers, sea urchins, sand dollars, etc. (~8,000 - 10,000 species) General characteristics: All echinoderms are marine All echinoderm adults have radial symmetry derived from bilaterally symmetrical larvae Nervous system diffuse, decentralized, usually of a nerve net, nerve ring, and radial nerves. Have separate sexes, although hermaphroditic species do exist Have a water vascular system composed of a series of fluid-filled canals, usually evident externally as muscular podia Kingdom Animalia – Phylum Echinodermata The water vascular system: Functions: Walking Gas exchange by diffusion Sensory Food manipulation Phylum Annelida • This phylum includes the segmented worms. • The most commonly known worms in this phylum are the Earthworm (class Oligochaeta) and the Leech (class Hirudinea) • Annelids are bilaterally symmetrical. General Characteristics • Entire body is divided internally and externally into segments. • The segment rings are called annuli. • The first segment is called the prostomium and the second is called the peristomium. These 2 segments form the head of the worm General Characteristics • They have a tube within a tube body plan. • Annelids have a fluid filled body cavity called a coelom which is lined with mesoderm. • They are the simplest of animals that have a true coelom. • The body of annelids & the remaining Phyla of animals have 3 germ layers. Characteristics of Arthropods • Segmented bodies divided into 3 regions; head, thorax & abdomen. • In some arthropods, the head and thorax is fused into a cephalothorax. Characteristics of Arthropods Jointed appendages that are always found in pairs. Exoskeleton is made of chitin. • Because the exoskeleton does not grow, young arthropods must periodically shed and replace its exoskeleton in a process called molting. • An exoskeleton limits the size of arthropods Characteristics of Arthropods • Complex movement and locomotion • Nervous system – Distinct dorsal brain and ventral nerve cord. • Adapted for land, water, and air • Well developed sense organs • Dorsal heart & open circulatory system • Terrestrial arthropods have holes in their exoskeleton to allow for breathing. These holes are called spiracles • There are many classes of arthropods but we will focus on these 5: – – – – – Crustacea Chilopoda Arachnida Diplopoda Insecta – Know the distinct characteristics of these 5 classes. Reproduction in Insects • All fertilization is internal. • Young develop in one of 2 ways. 1. Complete Metamorphosis • Insects such as moths, butterflies, bees, flies, beetles and ants. • Eggs hatch into segmented larvae. After several molts it passes into a resting stage called a pupa. • During this stage the tissues reorganize into the adult stage. • The 4 stages are egg → larva → pupa → adult. Complete Metamorphosis Incomplete Metamorphosis • Egg hatches into a nymph which is a small version of the adult with no wings. • The nymph is not able to reproduce. • The nymph goes through several molts until it reaches adult size. The final molt is when the wings and reproductive organs develop. • 3 stages of development: egg→ nymph→ adult