Chapter 28 An Introduction to Animal Diversity Characteristics of Most Animals • 1. multicellular eukaryotes • 2. cell specialization – (cells tissues organs) • • • • 3. heterotrophs 4. locomotion (sometime in lifecycle) 5. nervous + muscle systems (stimuli) 6. sexual reproduction – (large, nonmotile eggs; flagellated sperm) Marine Environments • Advantages – Buoyancy – support – Temperature – stable – Fluid + salt balance easily maintained • Challenges – Water movement/currents • Adapt: – – – – Strong swimmer – squid, fish, mammals Sessile Burrow in sand/silt Small body size plankton (food supply around as tossed) Other environments - problems • Fresh water – Water hypotonic to animal fluids • Osmoregulation - pump out water, keep salts (ATP) – Less constant – Less food – Oxygen and temp. vary – Turbidity + water volume change • Land – Desiccation • Adapt: body covering; respiratory surface deep within animal – Reproduction (desiccation) • Adapt: internal fertilization; shells on eggs; embryo in mom – Temperature extremes Body Symmetry • 2 types – Radial • wheel or cylinder form • Spokes from central axis – Cnidarians – jellyfish, sea anemones – Echinoderms – sea stars – Bilateral • Right and left halves – mirror images Fig. 32-7 (a) Radial symmetry (b) Bilateral symmetry Types of Body Cavities • Coelom = fluid-filled space between body wall and digestive tube • Acoelomate – No body cavity • Pseudocoelomate – Body cavity, not lined with mesoderm • Coelomate – Body cavity completely lined Fig. 32-2-3 Blastocoel Cleavage Endoderm Cleavage Blastula Ectoderm Zygote Eight-cell stage Gastrulation Blastocoel Cross section of blastula Gastrula Blastopore Archenteron 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 2 Main Groups of Coelomates • Protostomes – “first, the mouth” – Mollusks, annelids, arthropods • Deuterostomes – “second, the mouth” • Echinoderms, chordates Protostomes vs. Deuterostomes Cleavage • Protostomes – Spiral • Deuterostomes – radial Fig. 32-9a Protostome development (examples: molluscs, annelids) Eight-cell stage Spiral and determinate Deuterostome development (examples: echinoderms, chordates) Eight-cell stage Radial and indeterminate (a) Cleavage Protostomes vs. Deuterostomes Developmental Fate of the Embryo • Protostomes – “determinate” cleavage – Fixed early – Can only become certain cell types • Deuterostomes – “indeterminate” cleavage – Can adapt to become another cell type Fig. 32-9b Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) (b) Coelom formation Coelom Key Ectoderm Mesoderm Endoderm Archenteron Coelom Mesoderm Blastopore Solid masses of mesoderm split and form coelom. Blastopore Mesoderm Folds of archenteron form coelom. Protostomes vs. Deuterostomes Blastopore = (opening from outside to gut) • Protostomes – Develops into the mouth • Deuterostomes – Develops into the anus – Later, 2nd opening makes mouth 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 – Phylum Porifera • “to have pores” • Bodies – tiny holes • Marine Fig. 33-3a A sponge 3 main classes of sponges • Calcarea – Chalky, calcium carbonate spikes (spicules) • Hexactinellida (glass sponges) – 6-rayed spicules with silica • Demospongiae – Variable • Fibrous protein = spongin • Silica • OR spongin + silica Fig. 33-4 Choanocyte Osculum Flagellum Collar Food particles in mucus Choanocyte Azure vase sponge (Callyspongia plicifera) Spongocoel Phagocytosis of food particles Pore Epidermis Spicules Water flow Amoebocytes Mesohyl Amoebocyte Sponge Anatomy • Spongocoel – Central cavity – water flows • Ostia – Tiny pores, water enters • Osculum – Open end, water exits • Epidermal cells – Outer layer, line canals Sponge Anatomy • Canals – SA – food capture • Porocytes – Tube like cells – form pores – Regulate diameter by contracting • Collar cells Sponge Anatomy • Collar cells – Inner layer – Create water current, bring food and water to cells, carries away waste and CO2 – Trap and phagocytize food – Tiny collar at base of flagellum Sponge Anatomy • Mesohyl – Gelatin-like layer – Between inner and outer layers of sponge body • Amoebocytes – In mesohyl – Digestion, food transport, secrete spicules Sponge Feeding • Suspension feeders – Trap + eat whatever food the water brings – Water circulates in body – Food trapped on sticky collars of choanocytes – Food digested in collar or amoeboid cell – Undigested – out to water through osculum Gas exchange/Excretion • Diffusion – in/out of individual cells Response to Stimuli • No special nerve cells – can’t react as a whole • Individual cells can respond Reproduction of sponges • Asexual – Fragment or bud • Sexual – – – – Hermaphrodite – egg + sperm Some amoeboid cells become sperm, some eggs Eggs/sperm made at different times cross fertilize Sperm released into water, taken in by other sponges of same species – Fertilization and early dev. In mesohyl – Embryo moves to spongocoel, leaves with water – Swims, attaches to solid object sessile Cnidarians – Phylum Cnidaria • marine • Solitary • colonies Fig. 33-3b A jelly 3 classes of Cnidarians: • Hydrozoa – Hydras, hydroids – Polyp dominant • Scyphozoa – Jellyfish – Medusa dominant • Anthozoa – Sea anemones, corals – No medusa Fig. 33-7 (b) Jellies (class Scyphozoa) (a) Colonial polyps (class Hydrozoa) (c) Sea wasp (class Cubozoa) (d) Sea anemone (class Anthozoa) Body of Cnidarians • Radial symmetry • Hollow sac w/ mouth + surrounding tentacles at 1 end • Mouth leads to GV cavity (digestive) • Mouth – ingests food, expels waste • Epidermis – Protective covering • Gastrodermis – Lines gut, digestive • Mesoglea – Gelatinous, acellular – Separates epidermis + gastrodermis 2 body shapes of Cnidarians • Polyp – Dorsal mouth w/ tentacles – Hydra • Medusa – Mouth on lower oral surface – Jellyfish Fig. 33-5 Mouth/anus Polyp Tentacle Medusa Gastrovascular cavity Gastrodermis Body stalk Mesoglea Epidermis Tentacle Mouth/anus Response in Cnidarians • Nerve nets – Nerve cells that connect sensory cells in body wall to contractile + gland cells – Cells contacted, entire body responds – crunches in Feeding in Cnidarians (hydra) • Paralyze prey with Nematocysts – Nematocysts • • • • Stinging cells (“thread capsules”) In cnidocytes Stimulated – release coiled, hollow thread Sticky OR long and coil around prey OR barbs/spines • Prey pushed into mouth • GV cavity – digestion – Body motion helps circulate contents Fig. 33-6 Tentacle Cuticle of prey Thread Nematocyst “Trigger” Thread discharges Cnidocyte Thread (coiled) Gas exchange/Excretion • Diffusion – No cell far from surface Reproduction in Cnidarians • Asexual – Budding – good conditions – Colony – buds remain on parent • Sexual – Fall or stagnant water – Become males and females • Female – ovary – single egg • Male – testis - sperm – Zygote – may become covered with shell for winter 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) Comb Jellies – Phylum Ctenophora • • • • Marine Luminescent 8 rows cilia (comb) 2 tentacles – no nematocysts – adhesive glue cells • Radial symmetry • 2 cells layers w/ mesoglea • Mouth – food in; 2 anal pores – waste out (other end) Fig. 33-3d A ctenophore, or comb jelly Flatworms – Phylum Platyhelminthes • Flat, elongated, acoelomate • Bilateral symmetry • Cephalization – “head” at anterior – moves forward; eyespots • 3 germ layers – – ectoderm, mesoderm, endoderm • Muscular pharynx – Takes in food – 1 opening mouth Flatworms cont. • Nervous system – Simple brain = 2 mass nerve tissue = ganglia – connect to 2 nerve cords • Protonephridia – Osmoregulation, waste disposal • Complex reproductive organs • No organs for circulation, gas exchange – Diffusion through body wall Fig. 33-3e 1.5 mm Acoel flatworms (LM) Fig. 33-3f A marine flatworm 3 classes of Flatworms • 1. Turbellaria – Free-living – Planarians – pond • • • • Crossed eyes Auricles (“ears”) – locate food Carnivore – mouth, pharynx, GV cavity Reproduction – asexual – splits in 2 – Sexual – hermaphrodite – cross-fertilization Fig. 33-10 Pharynx Gastrovascular cavity Mouth Eyespots Ganglia Ventral nerve cords • 2. Trematoda + Monogenea – Flukes – blood + liver – Parasites – Hooks, suckers – attach to host – Complex reproduction Fig. 33-11 Male Female Human host 1 mm Motile larva Ciliated larva Snail host • 3. Cestoda – Intestinal parasite – Tapeworm – long, flat, ribbon-like – Suckers, hooks on scolex (head) – Body – proglottids (segments) • Each proglottid – male and female organs (100,000 eggs) – No mouth/digestive sys. – diffusion – Lacks sense organs Fig. 33-12 200 µm Proglottids with reproductive structures Hooks Sucker Scolex