Animals: The Invertebrates Chapter 25

Characteristics of Animals Characteristics of Animals Multicelled heterotrophic eukaryotes Multicelled heterotrophic eukaryotes Require oxygen for aerobic respiration Require oxygen for aerobic respiration Reproduce sexually, and perhaps asexually Reproduce sexually, and perhaps asexually Motile at some stage Motile at some stage Develop from embryos Develop from embryos

Major Animal Phyla Chordates Echinoderms Arthropods Annelids Mollusks Rotifers Roundworms Flatworms Cnidarians Sponges Multicelled Ancestry Radial Ancestry Bilateral Ancestry Coelomate Ancestry Single-celled, protistanlike ancestors Figure 25.2 Page 415

Symmetry Radial Bilateral Figure 25.3 Page 416 dorsal posterior ventral anterior

The Gut Region where food is digested and then absorbed Region where food is digested and then absorbed Saclike gut Saclike gut –One opening for taking in food and expelling waste Complete digestive system Complete digestive system –Opening at both ends; mouth and anus

Body Cavities - Acoelomate epidermis gut cavity no body cavity; region between gut and body wall packed with organs Figure 25.4a Page 417

Body Cavities - Pseudocoel epidermis gut cavity unlined body cavity (pseudocoel) around gut Figure 25.4b Page 417

Body Cavities - Coelom gut cavity peritoneum lined body cavity (coelom) Figure 25.4c Page 417

Segmentation Repeating series of body units Repeating series of body units Units may or may not be similar to one another Units may or may not be similar to one another Earthworms - segments appear similar Earthworms - segments appear similar Insects - segments may be fused and/or have specialized functions Insects - segments may be fused and/or have specialized functions

Animal Origins Originated during the Precambrian (1.2 billion million years ago) Originated during the Precambrian (1.2 billion million years ago) From what? Two hypotheses: From what? Two hypotheses: –Multinucleated ciliate became compartmentalized –Cells in a colonial flagellate became specialized

Phylum Placozoa One living species, Tricoplax adherens One living species, Tricoplax adherens Simplest known animal Simplest known animal Two-layer body, 3 mm across Two-layer body, 3 mm across Figure 25.5 Page 418

Sponges - Phylum Porifera No symmetry No symmetry No tissues No tissues No organs No organs Reproduce sexually Reproduce sexually Microscopic swimming larval stage Microscopic swimming larval stage

Sponge Structure central cavity water out water in flagellummicrovillinucleus glasslike structural elements amoeboid cell pore semifluid matrix flattened surface cells Figure 25.7a Page 419

Phylum Cnidaria Only animals that produce nematocysts Only animals that produce nematocysts Nerve net Nerve net Hydrostatic skeleton Hydrostatic skeleton Saclike gut Saclike gut Figure 25.8 Page 420 barbed thread inside capsule capsule’s lid at free surface of epidermal cell trigger nematocyst

Cnidarian Diversity Scyphozoans Scyphozoans –Jellyfish Anthozoans Anthozoans –Sea anemones –Corals Hydrozoans Hydrozoans

Two Main Body Plans Figure 25.9 Page 420 outer epithelium (epidermis) mesoglea (matrix) inner epithelium (gastrodermis) Medusa Polyp

Obelia Life Cycle (Hydrozoan) reproductive polyp female medusa male medusa sperm zygote ovum planula polyp forming feeding polyp Figure Page 421

Flatworms: Phylum Platyhelminthes Acoelomate, bilateral, cephalized animals Acoelomate, bilateral, cephalized animals All have simple or complex organ systems All have simple or complex organ systems Most are hermaphrodites Most are hermaphrodites

Three Classes Turbellarians (Turbellaria) Turbellarians (Turbellaria) Flukes (Trematoda) Flukes (Trematoda) Tapeworms (Cestoda) Tapeworms (Cestoda)

Planarian Organ Systems pharynx protonephridia flame cell nucleus cilia fluid filters through membrane folds flame cell opening of tubule at body surface Fig a,b Page 422

Planarian Organ Systems brainnerve cord genital pore oviduct testis ovary penis Fig cd Page 422

Roundworms (Nematoda) False coelom False coelom Complete digestive system Complete digestive system gonadpharynxintestine false coelom eggs in uterusanus muscularized body wall Figure Page 423

Flukes: Class Trematoda Parasitic worms Parasitic worms Complicated life cycle Complicated life cycle –Larval stage infects a mollusk –Adult infects a vertebrate Ciliated larva Worms mate in human host Fertilized egg Asexual reproduction in intermediate host Larvae form, leave snail Larvae bore into human skin Southeast Asian blood fluke Figure Page 424

Tapeworms: Class Cestoda Larvae encysted in muscle tissue Intermediate host Mature proglottid with fertilized eggs Scolex attaches to host intestinal wall Definitive host Figure Page 424

Rotifers Bilateral Bilateral Cephalized Cephalized False coelom False coelom Crown of cilia at head end Crown of cilia at head end Complete gut Complete gut Figure Page 425

Two Coelomate Lineages Protostomes Mollusks Mollusks Annelids Annelids Arthropods Arthropods Deuterostomes Echinoderms Echinoderms Chordates Chordates

Cleavage Patterns Protostome embryo (spiral cleavage) Deuterostome embryo (radial cleavage) In-text figure Page 426

Bilateral, soft-bodied, coelomate Bilateral, soft-bodied, coelomate Most have a shell or reduced version of one Most have a shell or reduced version of one Mantle drapes over body and secretes shell Mantle drapes over body and secretes shell Most have a fleshy foot Most have a fleshy foot Many have a radula for shredding food Many have a radula for shredding food Mollusks: Phylum Mollusca

Gastropods Gastropods Chitins Chitins Bivalves Bivalves Cephalopods Cephalopods Molluscan Diversity

Twisting of body parts during larval development Twisting of body parts during larval development Occurs only in gastropods Occurs only in gastropods Torsion mouth anus gill Figure Page 426

Body Plan of a Snail gill anus radula foot mantle cavity digestive gland mantle heart Figure Page 426

Body Plan of a Clam mouth retractor muscle left mantle retractor muscle foot palps left gill shell Figure Page 429

Cephalopods Only the nautilus retains external shell Only the nautilus retains external shell Other cephalopods are streamlined, active swimmers Other cephalopods are streamlined, active swimmers All move by jet propulsion All move by jet propulsion –Water is forced out of mantle cavity through a funnel-shaped siphon Have large brains relative to body size Have large brains relative to body size

Cuttlefish Body Plan Closed circulatory system with heart and accessory heart stomachkidney esophagus digestive gland brain arm jaw tentacleradula siphon anus ink sac gill heart accessory heart reproductive organ mantle internal shell Figure Page 429

Segmented, coelomate worms Class Polychaeta Class Polychaeta Class Oligochaeta Class Oligochaeta Class Hirudinea Class Hirudinea Annelids: Phylum Annelida

Polychaetes Most are marine Most are marine Bristles extend from paired, fleshy parapods on each segment Bristles extend from paired, fleshy parapods on each segment Head end is specialized Head end is specialized Fig c Page 430 “jaws” toothlike structures pharynx (everted) antenna palp (food handling) tentacle eyes chemical- sensing pit parapod

Predators and parasites Predators and parasites Less obvious body segmentation Less obvious body segmentation Most have sharp jaws Most have sharp jaws Leeches - Class Hirudinea Leeches - Class Hirudinea

No parapodia, few bristles per segment Earthworm - An Oligochaete Nerve cord Dorsal blood vessel Nephridium Coelom Circular muscle Longitudinal muscle Seta (retracted) Figure 25.25a Page 431

Earthworm Nephridium bladderlike storage region of nephridium nephridium’s thin loop reabsorbs some solutes, relinquishes them to blood blood vessels body wall external pore (fluid containing wastes discharged here) funnel (coelomic fluid with waste enters here) Figure 25.25b Page 431

Earthworm Circulatory System Hearts Figure 25.25c Page 431

Earthworm Digestive System Pharynx Esophagus Crop Gizzard Coelomic chambers Mouth Figure 25.25d Page 431

Earthworm Nervous System Brain Nerve cord Figure 25.25e Page 431

The phylum with the greatest number of species The phylum with the greatest number of species Four lineages: Four lineages: –Trilobites (all extinct) –Chelicerates (spiders, mites, scorpions) –Crustaceans (crabs, shrimps, barnacles) –Uniramians (insects, centipedes, millipedes) Arthropods: Phylum Arthropoda

Adaptations for Success Hardened exoskeleton Hardened exoskeleton Jointed appendages Jointed appendages Fused and modified segments Fused and modified segments Respiratory structures Respiratory structures Specialized sensory structures Specialized sensory structures Division of labor Division of labor Do not post on Internet Figure Page 432

Originated in seas Originated in seas A few are still marine: horseshoe crabs, sea spiders A few are still marine: horseshoe crabs, sea spiders The arachnids are all terrestrial The arachnids are all terrestrial Spiders Mites Scorpions Chiggers “Daddy longlegs” Ticks Chelicerates

Body Plan of a Spider eye poison gland chelicera mouth book lung sperm receptacle ovarysilk gland spinners anus Malpighian tubuledigestive glandheartbrain pedipalp Figure Page 433

Most are marine, some freshwater, a few terrestrial Most are marine, some freshwater, a few terrestrial Head has two pairs of antenna, three pairs of food-handling appendages Head has two pairs of antenna, three pairs of food-handling appendages Crustaceans Copepods Crayfish Barnacles Lobsters Shrimps Crabs Isopods (pillbugs)

Lobster Body Plan antennae (two pairs) one of two eyes fused segments of cephalothorax segments of abdomen tail fin swimmerets five walking legs (five pairs total) first leg food-handling appendages (three pairs) Figure 25.29a Page 434

Crab Life Cycle Larval and juvenile stages molt repeatedly and grow in size egg Figure Page 435

Millipedes and Centipedes Segmented bodies with many legs Segmented bodies with many legs Millipedes Millipedes –Two pairs of legs per “segment” –Scavengers Centipedes Centipedes –Flattened, with one pair of legs per segment –Predators

Insect Body Plan Thorax usually has three pairs of legs and one or two pairs of wings Thorax usually has three pairs of legs and one or two pairs of wings Abdomen contains most internal organs and specialized structure for reproduction Abdomen contains most internal organs and specialized structure for reproduction Three-part gut Three-part gut Malpighian tubules attach to midgut and serve in elimination of wastes Malpighian tubules attach to midgut and serve in elimination of wastes

Insect Headparts antenna labrum palps maxilla labium mandible Grasshopper Butterfly Fly Mosquito Figure Page 436

Insect Diversity The only winged invertebrates The only winged invertebrates More than 800,000 known species More than 800,000 known species Most successful species are small in size and have a great reproductive capacity Most successful species are small in size and have a great reproductive capacity

adult youngegg nymphs egg Growth and molting Incomplete metamorphosis Complete metamorphosis Types of Insect Development larvae pupa Different stages exploit different resources at different times

Unwelcome Arthropods Poisonous spiders Poisonous spiders Disease-carrying ticks Disease-carrying ticks Venomous scorpions Venomous scorpions Agricultural pests Agricultural pests Corn rootworm (Diabrotica virgifera) Do not post on Internet Figure Page 439

Echinoderms Deuterostomes Deuterostomes Body wall has spines or plates Body wall has spines or plates No brain No brain Adults are radial with bilateral features Adults are radial with bilateral features Do not post photos on Internet Figure Page 440 Sea urchin Sea cucumber Brittle star

Echinoderm Diversity Crinoids (sea lilies and feather stars) Crinoids (sea lilies and feather stars) Sea stars Sea stars Brittle stars Brittle stars Sea urchins, heart urchins, sand dollars Sea urchins, heart urchins, sand dollars Sea cucumbers Sea cucumbers

Body Plan of a Sea Star eyespot digestive gland gonad anus lower stomach upper stomach coelom sieve plate Figure 25.40a Page 441

Water Vascular System sieve plate ampulla Figure 25.40b Page 441