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SIMPLE ANIMALS All Animals • Heterotrophs that ingest their food • Multicellar formed from eukaryotic cells that lack plastids and cell walls • Move using contractile fibers • Most reproduce sexually by gametes produced by gonads: ovaries and testes Symmetry • Animals can be categorized according to the symmetry of their bodies, or lack of it – None – Bilateral – Radial • Two-sided symmetry is called bilateral symmetry • Bilaterally symmetrical animals have: – A dorsal (top) side and a ventral (bottom) side – A right and left side – Anterior (head) and posterior (tail) ends – Cephalization, the development of a head Fig. 32-7 (a) Radial symmetry (b) Bilateral symmetry Level of organization • Tissue • Organs • Organ systems Embryonic Tissues • Animal body plans also vary according to the organization of the animal’s tissues • Tissues are collections of specialized cells isolated from other tissues by membranous layers • During development, three germ layers give rise to the tissues and organs of the animal embryo • Ectoderm is the germ layer covering the embryo’s surface • Endoderm is the innermost germ layer and lines the developing digestive tube • Diploblastic animals have ectoderm and endoderm • Triploblastic animals also have an intervening mesoderm layer; these include all bilaterians Body Plan • None • Sac-like: one main opening • Tube-within-a-tube: mouth at one and end anus at the other Body Cavities • Most triploblastic animals possess a body cavity • A true body cavity is called a coelom and is derived from mesoderm • Coelomates are animals that possess a true coelom Fig. 32-8 Coelom Digestive tract (from endoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) (a) Coelomate Body covering (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Digestive tract (from endoderm) (b) Pseudocoelomate Body covering (from ectoderm) Tissuefilled region (from mesoderm) Wall of digestive cavity (from endoderm) (c) Acoelomate Fig. 32-8a Coelom Body covering (from ectoderm) Digestive tract (from endoderm) (a) Coelomate Tissue layer lining coelom and suspending internal organs (from mesoderm) • A pseudocoelom is a body cavity derived from the mesoderm and endoderm • Triploblastic animals that possess a pseudocoelom are called pseudocoelomates Fig. 32-8b Body covering (from ectoderm) Pseudocoelom Digestive tract (from endoderm) (b) Pseudocoelomate Muscle layer (from mesoderm) • Triploblastic animals that lack a body cavity are called acoelomates Fig. 32-8c Body covering (from ectoderm) Tissuefilled region (from mesoderm) Wall of digestive cavity (from endoderm) (c) Acoelomate Fate of the Blastopore • The blastopore forms during gastrulation and connects the archenteron to the exterior of the gastrula • In protostome development, the blastopore becomes the mouth • In deuterostome development, the blastopore becomes the anus Fig. 32-9c Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) Anus Mouth (c) Fate of the blastopore Key Digestive tube Anus Mouth Mouth develops from blastopore. Anus develops from blastopore. Ectoderm Mesoderm Endoderm Sponges: Porifera • Sponges are sedentary animals • They live in both fresh and marine waters • Sponges lack true tissues and organs • Sponges are suspension feeders, capturing food particles suspended in the water that pass through their body • Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food • Water is drawn through pores into a cavity called the spongocoel, and out through an opening called the osculum • Classified by type of Spicule which is the skeltal element they possess – Chalk sponges-calcium carbonate – Glass sponges-siliceous – Fibrous sponges-protienaceous Fig. 33-4 Food particles in mucus Flagellum Choanocyte Collar Choanocyte Osculum Azure vase sponge (Callyspongia plicifera) Spongocoel Phagocytosis of food particles Pore Epidermis Spicules Water flow Amoebocytes Mesohyl Amoebocyte • Sponges consist of a noncellular mesohyl layer between two cell layers • Amoebocytes are found in the mesohyl and play roles in digestion and structure • Most sponges are hermaphrodites: Each individual functions as both male and female • Some sponges produce asexual reproductive bodies called gemmules that are release into the water. Jellyfish, coral, anemonesPhylum Cnidaria • Cnidarians have diversified into a wide range of both sessile and motile forms including jellies, corals, and hydras • They exhibit a relatively simple diploblastic, radial body plan • The basic body plan of a cnidarian is a sac with a central digestive compartment, the gastrovascular cavity • A single opening functions as mouth and anus • There are two variations on the body plan: the sessile polyp and motile medusa Fig. 33-5 Mouth/anus Polyp Tentacle Medusa Gastrovascular cavity Endoderm Body stalk Mesoglea Ectoderm Tentacle Mouth/anus • Cnidarians are carnivores that use tentacles to capture prey • The tentacles are armed with cnidocytes, unique cells that function in defense and capture of prey • Nematocysts are specialized organelles within cnidocytes that eject a stinging thread Fig. 33-6 Tentacle Cuticle of prey Thread Nematocyst “Trigger” Thread discharges Cnidocyte Thread (coiled) Fig. 33-7 (b) Jellies (class Scyphozoa) (a) Colonial polyps (class Hydrozoa) (c) Sea wasp (class Cubozoa) (d) Sea anemone (class Anthozoa) Hydrozoans • Most hydrozoans alternate between polyp and medusa forms Fig. 33-8-3 Feeding polyp Reproductive polyp Medusa bud ASEXUAL REPRODUCTION (BUDDING) Portion of a colony of polyps Haploid (n) Diploid (2n) Gonad Medusa Egg SEXUAL REPRODUCTION Sperm FERTILIZATION Zygote 1 mm Key MEIOSIS Developing polyp Mature polyp Planula (larva) Flatworms- Phylum Platyhelminthes • Members of phylum Platyhelminthes live in marine, freshwater, and damp terrestrial habitats • Although flatworms undergo triploblastic development, they are acoelomates • They are flattened dorsoventrally and have a gastrovascular cavity • They can be parasites Turbellarians • Turbellarians are nearly all free-living and mostly marine • The best-known turbellarians are commonly called planarians • Planarians have light-sensitive eyespots and centralized nerve nets • The planarian nervous system is more complex and centralized than the nerve nets of cnidarians • Planarians are hermaphrodites and can reproduce sexually, or asexually through fission Fig. 33-10 Pharynx Gastrovascular cavity Mouth Eyespots Ganglia Ventral nerve cords Tapeworms • Tapeworms are parasites of vertebrates and lack a digestive system • Tapeworms absorb nutrients from the host’s intestine • Fertilized eggs, produced by sexual reproduction, leave the host’s body in feces • http://www.youtube.com/watch?v=T6pAfQInf2c Know This Nematodes • 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 • They have an alimentary canal, but lack a circulatory system • Reproduction in nematodes is usually sexual, by internal fertilization • Pseudocoelmate • Some parasitic • http://www.capcvet.org/capcrecommendations/ascarid-roundworm Know This Trichinella Ascaris Assignments • • • • • • Assignment 1-all Assignment 2-all Assignment 3-exclude j Assignment 4 Exclude 5 Make a chart of all key traits describe in lab book for the phyla discussed