1. Worms and Mollusks Chapter 27 Ridgewood High School scasatelli@ridgewood.k12.nj.us

2. 27.1 Flatworms (Platyhelminthes  Flatworms have: Soft-bodies Flattened bodies Tissues and internal organ systems The simplest animal to have 3 embryonic germ layers Bilateral symmetry Cephalization

3. Flatworms Body Organization  Flatworms are Acoelmates which are organisms with out a coelom. Coelom- a fluid filled body cavity that is lined with mesoderm (one of the germ layers)

5. Flatworms: Parasitic  Some flatworms are parasitic such as the Fluke. The fluke is thought to have evolved from free living ancestors. Many internal structures became adapted to parasitic conditions and many of the flatworms complexity was lost. Flukes are usually simpler then flatworms

6. Flatworms: Feeding  Free-living flatworms: Carnivores / scavengers  Tiny aquatic animals / recently dead animals Mouth: single opening for both food and waste Pharynx: muscular tube, that extends out of the mouth; pumps food into the cavity. Digested by the cells of the gut or digestive cavity Digested food is diffused from the gastrovascular cavity into other body tissues.

7. Flatworms (Parasitic): Feeding  Feed on blood, tissue fluids, or pieces of cells within the host’s.  Food is already digested by the host organism, therefore the parasitic worms do not need a complex digestive system.

8. Flatworms: Respiration, Circulation, Excretion  Circulation/Respiration: Diffuse oxygen and nutrients to internal tissues, remove CO 2 and other wastes from bodies.  Excretion: Flame Cells- specialized cells that filter and remove excess water from the body. Also remove ammonia and urea.

9. Flatworms: Response  Ganglia: groups of nerve cells that control the nervous system…located in the head Not complex enough to be a brain. Two long nerve cords run on each side of the flatworm and are connected by nerves that run across the body.  Eyespots: they detect changes in the amount of light in their environment

10. Flatworms: Movement  Two types of movement Cilia on their epidermal cells  Glide through the water and over the bottom of a stream or pond. Muscle cells  Controlled by the nervous system allow them to twist and turn

11. Flatworms: Reproduction  Hermaphrodite: an individual that has both male and female reproductive organs. Sexual Reproduction: two worms join in a pair, they both deliver sperm to each other, the eggs laid in clusters and hatch within a few weeks. Asexual Reproduction (common in free living): Fission: a process in which an organism splits into two halves and each half grows new parts to become a complete worm.

12. Groups of Flatworms  Turbellarians (free living): marine of freshwater, bottom dwellers.  Flukes (Trematoda-parasitic): found in the internal organs of a host, or blood, or external organs such as skin, mouth or gills.  Tapeworms (Cestoda-parasitic): long, flat, and live in the intestines of a host organism. Scolex: the head of an adult tapeworm and contain a structure that can contain suckers or hooks. (used to attach to the intestine wall) Proglottids: the segments of the worms body; contain both male and female reproductive organs.

13. 27.2: Roundworms (Nematoda)  Round  Slender  Unsegmented  Tappering ends  Psuedocoelom (“false coelom”)  Digestive tract with 2 openings Mouth and anus (the posterior opening of the digestive tract)

14. Roundworms: Feeding  Carnivorous Use grasping mouth parts and spines to catch and eat other small animals  Some eat algae or fungus or pieces of decaying organic matter.

15. Roundworms: Respiration, Circulation, & Excretion  Diffusion: exchange gases and excrete metabolic waste through body walls.  NO internal transport system

16. Roundworms: Response and Movement  Ganglia: several nerves extend from the ganglia (cluster of nerves located in the head) and run the length of body. Control movement Sense organs that detect chemicals given off by prey or hosts.  Muscles extend length of body; with fluid in the pseudocoelom-muscles function as a hydrostatic skeleton

17. Roundworms: Reproduction  Sexual Reproduction: most species have separate male and female organisms Internal fertilization: male deposits sperm inside the females reproductive tract.

18. Segmented Worms: Annelids  Segmentation Septa: are internal walls that separate each segment.  True coelom that is lined with mesoderm cells.  Setae: bristles that are attached to each segment to help movement.  Two openings: mouth and anus

19. Annelids: Feeding and Digestion  Filter feeders or carnivors  Carnivors: use pharynx to pump food and soil into a tube called esophagus. Food moves to the crop: where food is stored Then moves to the gizzard: where it is ground into smaller pieces.

20. Annelids: Circulation & Respiration  Closed Circulatory System: blood is contained within a network of blood vessels. Two major blood vessels that runs on top and bottom  Aquatic Annelids use gills: which are filamentous organs specialized for the exchange of gases underwater.  Land-dwellers use diffusion and exchange gases through their moist skin

21. Annelids: Excretion & Response  Digestive waste is removed via the anus.  Cellular waste containing nitrogen is eliminated by nephridia. Nephridia: which are excretory organs that filter fluid in the coelom.  Brain and well developed nervous system with several nervous cords. Eyes

22. Annelids: Movement  Hydrostatic Skeleton Longitudinal muscles: run from the front to the back of the worm  Make the worm shorter and fatter Circular muscles: wrap around each body segment  Contract and expand to make worm longer and thinner Marine Annelids: Parapodia are paddle-like appendages on each segment which they use from swimming and crawling

23. Annelids: Reproduction  Sexual Reproduction _____Fertilization with separate male and female organisms Some are hermaphrodites Two worms attach to each other, exchange sperm, and then store the sperm in special sacs When eggs are ready to be fertilized a clitellum (band of thickened, specialized segments) secretes a mucus ring into which the eggs and sperm are released. Fertilization takes place within the clitellum The ring then slips off the worm and forms a cocoon Worms hatch weeks later

24. Groups of Annelids  Oligochaetes (earthworms and their relatives) Streamlined bodies Few setae Soil and freshwater  Leeches Eternal parasites Eat blood and body fluids of their hosts  Polychaetes (sandworms, bloodworms) Marine Parapodia (paddle-like appendages) setea

25. 27.4: Mollusks  Soft-bodied  Internal or external shells  Include: snails, slugs, clams, squids, and octopi  Trochophore: free-swimming larval stage

26. Mollusks: Body Plan  Four Parts: Foot, mantle, shell, and visceral mass Muscular Foot: flat structure for crawling, spade- shaped foot for burrowing, and tentacles for capturing prey. Mantle: thin layer of tissue that covers most of the mollusks body Shell: made by glands in the mantle that secrete calcium carbonate Visceral Mass: located below the mantle consists of the organisms internal organs.

27. Mollusks: Feeding  Herbivors, carnivors, filter feeders, detritovors, or parasites. Radula: used by snails and slugs, a flexible tongue-shaped structure with hundreds of tiny teeth. Siphon: a tube-like structure through which water enters and leaves the body. (used by filter feeders)

28. Mollusks: Respiration & Circulation  Aquatic Organisms: Gills  Land-dwelling: diffusion  Open-Circulatory System and Closed- Circulatory System Open-Circulatory: blood is pumped through vessels by a simple heart and eventually leaves the vessels and works its way through the different sinuses. Sinus: a large saclike space.

29. Mollusks: Excretion & Response  Nephridia: removes ammonia from the blood and releases it outside the body  Clams (bivalves): simple nervous system with ganglia  Octopi (cephlapods): highly developed nervous system, with brain, and memory

30. Mollusks: Movement & Reproduction  Snails: secrete mucus along the base of the foot and then move over surfaces.  Octopus: jet propulsion  Bivalves: sexual reproduction (external fertilization), release eggs and sperm into open water. Develop into free-swimming larvae  Tentacles: internal fertilization in the female  Hermaphrodites: fertilize other organisms not themselves.

31. Group of Mollusks  Gastropods: (snails, sea hares, limpets) No shell or single-shelled, move using muscular foot  Bivalves: (clams, oysters, mussels, scallops) Two shells that are held together by one or two powerful muscles.  Cephalopods: (octopi, squids, cuttlefish, nautiluses) Soft-bodied, head is attached to single foot  Foot is divided into tentacles or arms  Eight of more tentacles.

32. MOLLUSKS