1. Platyhelminthes (Flatworms) General characteristics: – Body plan: acoelomate, bilateral symmetry Habitat: aquatic Nutrition: many are parasites, feed off host(blood, tissue, or predigested materials from host’s intestines) feed on dead animals Feeding: Planarians extend pharynx from mouth Examples: Turbellaria (Planarian) Trematoda (Fluke) Cestoda (tapeworm)

2. Digestion: extracellular, food is pumped into digestive cavity or gut and cells digest and absorb nutrients, digested food is then diffused into the other body tissue Respiration and Circulation: Diffusion of gases through the skin, skin must remain moist Excretion: diffusion through the body wall – planarians have flame cells to excrete water and wastes through pores

3. Freshwater flatworms have simple ganglia and nerve cords that run the length of the body. 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. Flatworms use a pharynx to suck food into the gastrovascular cavity. Digested food diffuses from the cavity into other cells of the body. Eyespots in some species detect light. Eyespot Head Gastrovascular cavity Ganglia Nerve cords Excretory system Mouth Pharynx Ovary Testes Excretory tubule Flame cell The Anatomy of a Flatworm

4. Nervous: Planaria: ganglia (mass of nervous tissue), eyespots, sensory lobes respond to touch and chemicals – Demostrates cephalization, nervous tissue is concentrated in the head region.

5. Reproduction: Hermaphrodites – Asexual reproduction fission (worm splits into two ) – Sexual reproduction exchange sperm, internal fertilization – Parasitic worms require hosts to reproduce Tapeworm

6. Section 27-1 Flukes mature and reproduce sexually in the blood vessels of human intestines. Embryos are released and passed out with feces. Once in the water, embryos develop into swimming larvae that infect an intermediate host (snail). After asexual reproduction, new larvae are released from the snail into the water. They then infect humans, the primary host, by boring through their skin. Primary host (human) Intermediate host (snail) Human intestine Adult fluke Embryo Ciliated larva Tailed larva Other information: Schistosome Life Cycle Shistosomiasis

7. Mobility: – Cilia for gliding – Muscle cells controlled by nervous system to react to stimuli

8. Nematoda (Roundworms) General characteristics: – Pseudocoleomate – long and slender, tapered at both ends – Roundworms are protostomes – bilateral symmetry – Body is covered in a complex cuticle Habitat/Nutrition: Parasites that live in the intestines Feeding – Both mouth and anus connected by digestive tube Examples: hookworms, pinworms, guinea worms

9. Digestion: takes place in digestive cavity, digested food diffuses into other body tissue. – May also have digestive sacs that food is pumped into for digestion. Circulation and Respiration: Diffusion of gases through the skin Excretion: Canal system, diffusion through body wall or out through mouth Nervous: simple nervous system, with a main ventral (belly) nerve cord and smaller dorsal (back) nerve cord

10. Reproduction: – Sexual, internal fertilization – usually separate sexes – Genders differ in size, shape and color – Parasitic require host Over 1/3 of human population potentially infested with these worms!

11. Mobility: Muscles along body wall for movement Hookworm egg Male Whipworm Pinworm eggs

12. Annelidia General characteristics: – Coelomates – Known for segmented body – Earthworms, leeches, and marine worms are common examples. – Best developed sense organs in free living marine organism blood vessels muscle hearts brain mouth digestive tract nerve cord segment

13. Habitat: aquatic and moist soil Nutrition: heterotrophic, filter feeders, parasites, scavengers – Feed on recently dead animals, blood, host’s body Feeding: Pharynx used to obtain food – Carnivorous species have two or more sharp jaws

14. Digestion: extracellular, takes place in intestine – Earthworm: pharynx → esophagus→ crop (storage) → gizzard (ground) → intestines (absorption) Circulation: – closed (blood contained in vessels) Respiration: – Aquatic: breathe through gills – Land dwellers: diffusion through skin (must stay moist) typically secrete a mucus to keep skin moist

15. Excretion: – Digestive wastes pass out through the anus – Cellular wastes containing nitrogen is passed out by the nephridia (simple kidney)

16. Section 27-3 Anus Clitellum Circular muscle Longitudinal muscle Nephridia Ganglia Ring vessels Reproductive organs Ventral blood vessel Ganglion Brain Mouth Dorsal blood vessel Crop Gizzard Body segments Setae

17. Nervous: – Well developed nervous systems consisting of brain and spinal cord – Two or more pairs of eyes, sensory tentacles, chemical receptors and statocysts that help detect gravity Reproduction – Most sexually – Some use external fertilization and have separate sexes – Earth worms and leeches are hermaphroditic, but rarely fertilize their own eggs

18. Mobility – Two major groups of muscles that function as part of the hydrostatic skeleton – Longitudinal and circular muscles, move by alternating contractions – Marine worms have parapodia to use for swimming and crawling