27–1 Flatworms

1. 27–1 Flatworms A. What Is a Flatworm? B. Form and Function in Flatworms 1. Feeding 2. Respiration, Circulation, and Excretion 3. Response 4. Movement 5. Reproduction C. Groups of Flatworms 1. Class Turbellaria (free-living flatworms) 2. Class Trematoda (parasitic flukes) 3. Class Cestoda (parasitic tapeworms)

2. Invertebrate Phylogeny Invertebrate Cladogram WORMS Chordates Cladogram (shows evolutionary relationships) Echinoderms Arthropods Annelids Mollusks RadialSymmetry Roundworms Flatworms Pseudocoelom Deuterostome Development Cnidarians Radial Symmetry Coelom Protostome Development Sponges Three Germ Layers & Bilateral Symmetry Tissues Multicellularity Single-celled ancestor

3. Cladogram of Six Kingdoms and Three Domains DOMAIN ARCHAEA DOMAIN EUKARYA Kingdoms Eubacteria Archaebacteria Protista Plantae Fungi Animalia DOMAIN BACTERIA Platyhelminthes (flatworms) Nematoda (roundworms) Molluska (snails, clams, octopus) skip Annelida (segmented worms)

4. Phylum Platyhelminthes “flatworms” What Is a Flatworm? • Flatworms are soft, flattened worms that have tissues and internal organ systems. They are the simplest animals to have: • three embryonic germ layers • bilateral symmetry • cephalization (head) • Flatworms are known as acoelomates meaning “without coelom”. A coelom is a fluid filled body cavity. Flatworms do not have a fluid filled body cavity. marine flatworm planaria tapeworm

5. The Anatomy of a Flatworm Eyespots in somespecies detect light. Eyespot Ganglia Head Nervecords Gastrovascularcavity Freshwater flatworms have simple ganglia and nerve cords that run the length of the body. Excretorysystem Uses a pharynx to suck food into the gastrovascular cavity. Digested food diffuses from the cavity into other cells of the body. Ovary Testes Mouth Pharynx The excretory system consists of a network of tubules connected to flame cells that remove excess water and cell wastes. Most flatworms are hermaphrodites, having male reproductive organs (testes) and female reproductive organs (ovaries) in the same organism. Flame cell Excretorytubule

6. Form and Function in Flatworms

7. Groups of Flatworms

8. Primary host (human) Intermediate host(snail) Life Cycle of Schistosoma Mansoni (blood fluke) Flukes mature and reproduce sexually in the blood vessels of human intestines. Embryos are released and passed out with feces. Adult fluke Human intestine Embryo Ciliated larva Tailed larva After asexualreproduction, newlarvae are releasedfrom the snail into the water. They then infect humans, the primary host, by burrowing through the skin. If they get into the water, embryos develop into swimming larvae that infect an intermediate host (snail).

9. 27–2 Roundworms A. What Is a Roundworm? B. Form and Function in Roundworms 1. Feeding 2. Respiration, Circulation, and Excretion 3. Response 4. Movement 5. Reproduction C. Roundworms and Human Disease 1. Trichinosis-Causing Worms 2. Filarial Worms 3. Ascarid Worms 4. Hookworms D. Research on C. elegans

10. Phylum Nematoda “roundworms” What Is a Roundworm? • Roundworms are slender, unsegmented worms that have: • pseudocoeloms (false coelom) • digestive systems with two openings (a mouth and an anus) • Roundworms have a tube-within-a-tube body plan. The inner tube is the digestive tract, and the outer tube is the body wall. Food moves in one direction through the digestive tract. roundworm Trichinella

11. Form and Function in Roundworms

12. Diseases Caused by Roundworms Section 27-2 ORGANISM Trichinella Filiarial worms Ascaris Hookworms DISEASE Trichinosis Elephantiasis Ascaris infection/infestation Hookworm infection/infestation ROUTE OF INFECTION Eating undercooked meat containing larval cysts Bite of insect carrying filarial worms Eating unwashedfood contaminatedwith Ascaris Bare skin in contact with contaminated soil DESCRIPTION Larvae burrow into tissues of host, causing pain Worms block passage of fluids within lymph vessels, causing tissues to swell Worms in intestine block normal passage of food and absorption of nutrients Worms attach to intestinal wall and suck blood, causing weakness and poor growth

13. 27–3 Annelids A. What Is an Annelid? B. Form and Function in Annelids 1. Feeding and Digestion 2. Circulation 3. Respiration 4. Excretion 5. Response 6. Movement 7. Reproduction C. Groups of Annelids 1. Oligochaetes 2. Leeches 3. Polychaetes D. Ecology of Annelids

14. Phylum Annelida“segmented worms” What Is an Annelid? • Annelids have: • a segmented body • a true coeloms (body cavity) that is lined with tissue derived from mesoderm. • There are 3 groups of Annelids • Class Oilochaeta (earthworms and their relatives) • Class Hirudinea (leeches) • Class Polychaete (sandworms, bloodworms, & relatives) earthworm Leech

15. Form and Function in Annelids

16. Groups of Annelids

17. Ecology of Worms • Earthworms burrow through the soil, aerating it, and mixing the topsoil. Their tunnels provide passageways for plant roots and water and allow the growth of beneficial bacteria. Earthworm castings (waste) are rich in nitrogen and nutrients that fertilize the soil. They are also important food sources for birds, moles, skunks, snakes, toads, etc. • In the sea, marine annelids are an important part of the food chain. Their larvae are animal plankton consumed by fish. Adult worms are eaten by crabs, fish, and other marine life. Some marine annelids are filter feeders that clean ocean water.

18. Comparing Flatworms, Roundworms, and Annelids CHARACTERISTIC Shape Segmentation Body cavity Digestion and excretion Respiration FLATWORMS Flattened No Acoelomate Gastrovascular cavity with one opening only; flame cells remove metabolic wastes Through skin; no respiratory organs ROUNDWORMS Cylindrical with tapering ends No Pseudocoelomate Tube-within-a-tube digestive tract; opening at each end; metabolic wastes excreted through body wall Through skin; no respiratory organs ANNELIDS Cylindrical with tapering ends Yes Coelomate Tube-within-a-tube digestive tract; opening at each end; nephridia remove metabolic wastes Through skin; aquatic annelids breathe through gills Section 27-3 CHARACTERISTIC Circulation Response Movement Reproduction FLATWORMS No heart, blood vessels,or blood Simple brain; nerve cords run length of body; eyespot and other specialized cells that detect stimuli Gliding, twisting,and turning Sexual (hermaphrodites); asexual (fission) ROUNDWORMS No heart, blood vessels,or blood Several ganglia in head region; nerve cords run length of body; several types of sense organs Thrashing Sexual (primary males and females) ANNELIDS Blood circulated through blood vessels in closed circulatory system Well-developed nervous system with brain and several nerve cords; many sense organs Forward peristaltic movement Sexual (some are hermaphrodites; some have separate sexes)

19. 27–4 Mollusks A. What Is a Mollusk? B. Form and Function in Mollusks 1. Body Plan 2. Feeding 3. Respiration 4. Circulation 5. Excretion 6. Response 7. Movement 8. Reproduction C. Groups of Mollusks 1. Gastropods 2. Bivalves 3. Cephalopods D. Ecology of Mollusks

20. Cladogram of Six Kingdoms and Three Domains DOMAIN ARCHAEA DOMAIN EUKARYA Kingdoms Eubacteria Archaebacteria Protista Plantae Fungi Animalia DOMAIN BACTERIA Molluska (snails, clams, squid, octopus)

21. Phylum Mollusca“soft-bodied” snail Class Gastropoda “stomach foot” What Is a Mollusk? • Mollusks are soft-bodied animals that usually have an internal or external shell. Four body parts. • Foot (muscle for movement) • Mantle (secretes shell) • Shell (protection) • Visceral mass (organs) • Many aquatic mollusks have free-swimming larvae called a trochophore, which has at least one band of cilia encircling its body. • Mollusks and Annelids shared a common ancestor more than 550 million years ago. scallop Class Bivalvia “two shells” octopus Class Cephalopoda “head foot”

23. Form and Function in Mollusks

24. The Mollusk Body Plan Section 27-4 Squid (Cephalopod) Snail (Gastropod) Shell Mantle cavity Foot Gills Digestive tract Clam (Bivalve) Earlymollusk

25. The Anatomy of a Snail (Gastropod)

26. Coelom Stomach Heart Shell Nephridium Adductor muscle Mouth Anus Excurrentsiphon Adductormuscle Incurrentsiphon Gills Mantle cavity Intestine Mantle cavity Foot The Anatomy of a Clam (Bivalve) Section 27-4

27. The Anatomy of a Squid (Cephalopod)

28. 3 Major Groups of Mollusks Comparing the Three Major Groups of Mollusks MOLLUSK GROUP Gastropods Bivalves Cephalopods SHELL Shell-less orsingle-shelled Two shells held together by oneor two muscles Internal shell orno shell FOOT Muscular foot located on ventral side and used for movement Burrowing species have muscular foot. Surface-dwelling species have either no foot or a “reduced” foot. Head is attached to a single foot. The foot is divided into tentacles or arms. EXAMPLES Snail, slug, sea hare, nudibranch Clam, oyster, mussel, scallop Octopus, squid, cuttlefish, nautilus

29. Ecology of Mollusks • Filter feeders, like clams, clean the water. Bivalves filter pollutants, so they can be used to monitor water quality. • Some mollusks have symbiotic relationships with algae or to parasites. • Mollusks are an important food source for humans. (clams, squid) • Some snails and slugs never develop cancer, so they are studied for medical research.