1. Ms. Moore 2/11/13

2. What is a flatworm?  Phylum: Platyhelminthes  Flatworms are soft, flattened worms that have tissues and internal organ systems.  They are the simplest animals to have 3 embryonic germ layers, bilateral symmetry, and cephalization.  Acoelomates: without coelom (fluid-filled body cavity, lined with tissue from mesoderm

3. Flatworms: Form and Function  Feeding:  Carnivores or Scavengers ; can be parasitic  Digestive cavity with single opening (mouth)  Pharynx: extends outside the mouth and pumps food into digestive cavity (gut)  Food diffuses from the digestive cavity into all other body tissues

4.  Respiration, Circulation, and Excretion:  Since their bodies are so flat and thin, many flatworms do not need a circulatory system to transport materials (use diffusion).  No gills or respiratory organs; no heart, blood vessels, or blood.  Flame cells: specialized cells that remove excess water from the body; filter and remove ammonia and urea using pores of the skin

5.  Response:  Ganglia: groups of nerve cells that control the nervous system (no brain)  Eyespot: group of cells that can detect changes in the amount of light in their environment

6.  Movement:  Cilia on the epidermal cells help glide through the water.  Muscles controlled by the nervous system help to twist and turn to react to environment.

7.  Reproduction:  Hermaphrodite: both male and female reproductive organs  Sexual: two worms join in a pair and they deliver sperm to each other  Asexual: fission  organism splits in two and each half grows new parts to become a complete organism

8. Groups of Flatworms  Turbellarians  Flukes  Tapeworms

9. Turbellarians  Free-living flatworms  Most live in marine or fresh water  Bottom dwellers: living in sand or mud  Planarians: “cross-eyed” freshwater worms

10. Flukes  Class: Trematoda  Parasitic flatworms that infect internal organs of their host; can also be external parasites.

11. Tapeworms  Class: Cestoda  Long, flat, parasitic worms that are adapted to life inside the intestines of their hosts.  Scolex: contains suckers or hooks; attaches  Proglottids: segments that make up most of worm’s body; contain male and female reproductive organs  Youngest proglottids are at the anterior end and the largest and most mature are at t he posterior. After eggs have been fertilized, proglottids break off and release zygotes that are passed out of the host in feces/  Testes: fertilize eggs of other tapeworms or of self

12. What is a Roundworm?  Phylum: Nematoda  Roundworms are slender, unsegmented worms with tapering ends; Range in size from microscopic to a meter in length  Pseudocoelom: false coelom (only partially lined with mesoderm  Digestive tract with two openings—mouth and anus (posterior opening of digestive tract)  “tube within a tube”: inner tube is digestive tract and outer tube is body wall  Food moves in one direction

14. Roundworms: Form and Function  Feeding:  Carnivorous: eat small animals by latching on to them with grasping mouth parts and spikes  Scavengers: eat algae or decaying mater  Consume bacteria and fungi  The free living roundworms tend to be more complex than parasitic roundworms.

15.  Respiration, Circulation, and Excretion  Diffusion through body walls  Response  Simple nervous systems with several ganglia; sense organs that detect chemicals given off by prey or host  Movement  Muscles extend length of body; function as hydrostatic skeleton  Reproduction  Sexually with male and female worms  Internal fertilization

16. Roundworms and Human Disease  Trichinosis-Causing Worms  Caused by Trichinella roundworm  Worms burrow into intestine walls and females release larvae that travel through the bloodstream and live in organs and tissues of host’s body

18.  Filarial Worms  Found in tropic regions of Asia; live in blood and lymph vessels of birds and mammals (humans)  Transmitted host-to-host by biting insects like mosquitoes  Large numbers could block lymph passages  elephantiasis

19.  Ascarid Worms  The cause of malnutrition of more than 1 billion people worldwide.  Ascaris lumbricoides usually spread by eating vegetables that are not washed properly.

20.  Hookworms  25% of the world’s population is infected with these worms  Eggs hatch outside the body and mature in the soil  Use tooth-like plates to burrow into skin of an uncovered foot and live in bloodstream  Suck blood and cause weakness and poor growth

22. Research on C. elegans  DNA sequence has been mapped out (97 million bp)  Help us find out how eukaryotes become multicellular and how multicellular animals are similar and different

23. What is an Annelid?  Phylum: Annelida; “little ring”  Septa: internal walls between each body segment  Setae: bristles attached to each segment  Annelids are worms with segmented bodies  Have true coelom that is lined with tissue derived from mesoderm.  Like roundworms, annelids have a tube within a tube system with an anus.

25. Annelids: Form and Function  Feeding and Digestion  Range from filter feeders to predators  Use a pharynx that hold two or more sharp jaws used to attack prey.  Earthworms: pharynx pumps food into esophagus  moves to crop (storage)  through gizzard (ground into smaller pieces)  intestine

26.  Circulation  Closed Circulatory System: blood is contained within a network of blood vessels  Earthworm: blood circulates through two major blood vessels  Dorsal runs to head; ventral runs to tail  Dorsal functions as a heart due to contractions = pump blood

27.  Respiration  Aquatic annelids breathe through gills  Land-dwelling annelids take in oxygen and give off carbon dioxide through moist skin; mucus  Excretion  Digestive waste passes through the anus  Cellular waste eliminated by nephridia (excretory organs that filter fluid in the coelom)

28.  Response  Brain and nerve cords  Marine annelids are more developed: sensory tentacles, chemical receptors, statocyts, two or more pairs of eyes  Movement Movement  Hydrostatic skeleton  Longitudinal muscles: front to rear; muscles contract to make worm shorter and fatter  Circular muscles: contract to make worm longer and thinner  Marine annelids: paddle like appendages (parapodia)

29.  Reproduction  Sexually: external fertilization  Hermaphrodites: two worms exchange sperm and store them in special sacs  Clitellum: band of thickened, specialized segments, secretes a mucous ring into which sperm and egg are released; rings slips off and forms a cocoon; worms hatch weeks later

30. Groups of Annelids  Class: Oligochaetes  Annelids that typically have streamlined bodies and relatively few setae; soil or freshwater  Castings: mixture of sand, clay and undigested food that an earthworm expels from its anus.

31.  Class: Hirudinea  Leeches  External parasites that suck the blood and body fluids of their host  ¼ are carnivorous that that feed on soft-bodies invertebrates  Suckers at both ends of body  Proboscia: muscular extension that can be forced into tissue of host  Can release a substance that anesthetizes wound and prevents blood from clotting.

32.  Class: Polychaeta  Polychaetes  Marine annelids that have paired, paddle like appendages tipped with setae

33. Ecology of Annelids  Earthworms (and other annelids) burrow through soil, aerating it and mixing it to depths of two meters or more  Mine minerals from deeper soil layers  Diets of many birds and other vertebrates

34. What is a Mollusk?  Phylum: Mollusca  Mollusks are soft-bodied animals that usually have an internal or external shell.  Ex: snails, slugs, clams, squids, and octopi.  Trochophore: free-swimming larval stage  Characteristic of Annelida = related 550 m.y.a.

35. Form and Function: Mollusks  True coeloms and organ systems  Body Plan (4 basic parts):  Foot: muscular structure used for crawling, burrowing, and capturing prey  Mantle: thin layer of tissue that covers the body (cloak)  Shell: glands in mantle secrete calcium carbonate; reduced or lost in slugs and other mollusks  Visceral Mass: beneath mantle; consists of internal organs (Figure 27-21)

37.  Feeding:  Can be herbivores, carnivores, filter feeders, detritivores, or parasites  Radula: flexible tongue-shaped structure used by snails and slugs; 100s of teeth are attached  Octopi use sharp jaws and tentacles to feed  Clams, oysters, and scallops filter feed with their gills and mucus  Siphon: tube like structure where water enters and leaves the body

38.  Respiration:  Use gills inside their mantle cavity  Land species have no gills, but they do have thin blood vessels in mantle that stay moist for oxygen passage.  Circulation: open or closed  Open circulatory system: blood is pumped through blood vessels by a simple heart; the blood makes way through body to the gills, then back to the heart; found in slow moving mollusks  Closed circulatory system: used in fast-moving mollusks bc it moves blood through body faster  Excretion:  Cells release wastes into blood and nephridia remove it from the body

39.  Response:  Slugs use simple ganglia and octopi use complex brain  Complex brain allow them to remember things and be trained for reward or avoid punishment  Movement:  Slugs secrete mucus and use their foot to glide  Octopi use jet propulsion  Reproduction:  Sexually by internal or external fertilization  Can be hermaphrodites, but do not fertilize own eggs

40. Groups of Mollusks  Gastropods  Class: Gastropoda  Gastropods are shell-less or single-shelled mollusks that move by using a muscular foot located on the ventral side  EX: snails, land slugs, sea butterflies, and sea horses  Protection: some can retract back into their shell or use ink to make a smoke screen; some produce chemicals that make them taste bad; nudibranchs can recycle nematocysts and use them

41.  Bivalves  Class: Bivalvia  Bivalves have 2 shells held together by one powerful muscle  EX: clams, oysters, mussels, and scallops  Most stay in one spot for long periods of time, except scallops (move to run from predators)  Eat through filter feeding or sifting through the mud.

42.  Cephalopods  Class: Cephalopoda  Cephalopods have a head that is attached to their foot which is divided into tentacles or arms (8+).  EX: octopus, squids, cuttlefishes, nautiluses  Nautiluses are the only ones with external shells; they have over 90 tentacles; control water depth by amount of gases in their mantle  Octopi have lost shells completely  Cuttlefishes have small shells inside their body

43. Ecology of Mollusks  Mollusks can be used to detect water quality  Filter algae out of the water  Live symbiotically with other organisms  Major food source for humans