Inquiry Lesson Part 3

1. Inquiry Lesson Part 3 Worm Anatomy Benchmark SC.6.L.14.5 Students will identify the major body systems and describe ways these systems interact with each other to maintain homeostasis.

2. Content Statement Earthworms have body systems with organs that work together to perform essential tasks that help the earthworm to survive.

3. Vocabulary Review • invertebrate • free-living organism • bilateral symmetry • hermaphrodite • dorsal • ventral • anterior • posterior • clitellum • prostomiun

4. Dissection Safety • Do not engage in horseplay! Common sense should rule here when working with sharp instruments. • Remain seated at your lab station and LISTEN to all directions. • Pin the specimen to be dissected securely in the dissecting pan or tray.  Never dissect while holding the specimen in your hand(s). • Wear safety goggles and a gloves to protect against biological hazards. • Point sharp objects or tools away from yourself and others. • Do not use excess force when working with a sharp instrument such as a scalpel. • Use dissecting scissors instead of a scalpel whenever possible. It tends to cut more efficiently for most work and is less dangerous to use. • Make certain to return your dissection tools to their appropriate container.  Care for and dispose of your dissection in accordance with the directions given by your instructor. • Do not eat or drink in a laboratory where a dissection is occurring. • WASH YOUR HANDS!

5. Nervous System • Why is it important? The nervous system transmits signals through the body that help the worm to move and to respond to stimuli. • Major Parts: • Ganglia (simple brain) • Ventral Nerve Chord • Nerve Collar

6. Nervous System • The nerve collar or “brain” is important for movement: if the brain of the earthworm is removed, the earthworm will move continuously. If the first ventral ganglion is removed, the earthworm will stop eating and will not dig. Each segmented ganglion gets sensory information from only a local region of its body and controls muscles only in this local region. Earthworms have touch, light, vibration and chemical receptors all along the entire body surface

7. Nervous System • The nervous system of the earthworm is "segmented" just like the rest of the body. It consists of the ventral nerve cord, which travels the length of the worm on the ventral side. A series of ganglia, which are masses of tissue containing many nerve cells, are found in each of the worm’s segments. The nerve collar surrounds the pharynx and consists of ganglia above and below the pharynx.

8. Nervous System Note: To see the nerve chord, the digestive stem must be removed. It looks like a thin white string that runs along the length of the earthworm.

9. Reproductive System • Why is it important? Reproduction is one of the most important and fundamental properties of living organisms by which every kind of living organism multiplies to form new individuals of it’s own kind. In this process, one generation of living organisms gives rise to the next generation. This process is not essential to the life of any individual but is a function essential for the life of the species. • Major Parts: • Clitellum • Ovaries • Testes • Seminal vesicles • Genital pores

10. Reproductive System • During mating, sperm from one worm travel along the sperm grooves to the seminal receptacles of another worm. Fertilization of the eggs takes place outside the body as the cocoon moves forward over the body, picking up the eggs of one worm and the sperm of its mate

11. Reproductive System • The clitellum is a swelling of the body found in sexually mature worms and is active in the formation of an egg capsule, or cocoon. Eggs are produced in the ovaries and pass out of the body through femalegenital pores. Sperm are produced in the testes, stored in the seminal vesicles and pass out through tiny male genital pores. NOTES: The seminal vesicles will be among the first things you see. They are creamy white “blobs” that cover the part of the digestive system.

12. Digestive System • Why is it important? The primary function of the earthworm’s digestive system is to break down the food into smaller parts so the body can use them to build and nourish cells and provide energy. This system also rids the body of solid wastes called castings. • Major Parts: • Mouth • Pharynx • Esophagus • Crop • Gizzard • Intestine • Anus

13. Digestive System • The earthworm takes in a mixture of soil and organic matter through its mouth, which is the beginning of the digestive tract. The mixture enters the pharynx. The esophagus, acts as a passageway between the pharynx and the crop. The crop stores food temporarily. The mixture that the earthworm ingests is ground up in the gizzard. In the intestine, which extends over two-thirds of the body length, digestion and absorption take place. Soil particles and undigested organic matter pass out of the worm through the anus.

14. Digestive System Mouth Note: It will be difficult to observe the pharynx and esophagus. The gizzard, located posterior to the crop, is harder than the rest of the digestive system. Be sure to open up the crop and gizzard to see what is inside!

15. Castings • Rich digested organic soil that earthworms leave behind

16. Worm Digestive Systems One-way Digestive System Two-way Digestive System anus

17. Circulatory System • Why is it important? The primary function of the earthworm’s circulatory system is to move blood to where it can be oxygenated and to where wastes can be disposed. Circulation then serves to bring newly oxygenated blood to the tissues of the body. As oxygen and other chemicals diffuse out of the blood cells and into the fluid surrounding the cells of the body's tissues, waste produces diffuse into the blood cells to be carried away. • Major Parts: • 5 Aortic arches (hearts) • Dorsal Blood Vessel • Ventral Blood Vessel

18. Circulatory System • Earthworm’s have a closed circulatory system. Blood vessels carry blood throughout the earthworm’s body. The pumping organs of the circulatory system are five aortic arches. Blood travels from the arches through the ventral blood vessel to capillary beds in the body. The fluids then collect in the dorsal blood vessel and reenter the aortic arches. Aortic Arches

19. Excretory System • Why is it important? The primary function of the earthworm’s excretory system is to remove liquid waste from its body. • Major Parts: • Nephridia • Bladder-like storage region • External pores

20. Excretory System • Excretory functions are carried on by nephridia, which are found in pairs in each body segment. Like kidneys, they work to remove liquid wastes from the inside the earthworm’s body. They appear as tiny white fibers on the dorsal body wall. In earthworms, members of the phylum Annelida, the excretory system consists of structural units called nephridia. Each nephridium contains a ciliated tunnel that leads to a long, coiled tubule, which leads to a bladderlike sac (a primitive bladder). Fluid moves from the internal environment into the funnel. As fluid passes through the tubule, cells in the tubular lining absorb useful compounds such as glucose, amino acids, and salts. The remaining materials constitute metabolic waste, and they are passed into the bladderlike sac. The sac later opens through a pore in the earthworm's skin where the liquid waste products are discharged.

21. Excretory System Note: Most parts of the earthworm’s excretory system will be too small for you to observe.

22. Respiratory System • Why is it important? The primary function of the earthworm’s respiratory system is to supply the blood with oxygen and to remove carbon dioxide from blood. • Major Parts: • Skin Note: You will not observe any respiratory organs inside the worm.

23. Respiratory System • The earthworm has no gills or lungs. Oxygen and carbon dioxide are exchanged between the circulatory system and the environment through the moist skin in a process called diffusion. To stay moist, earthworms secrete both mucus and liquid from body pores.