Earthworm Dissection Worksheet Answers Guide for Biology Students

Earthworm Dissection Worksheet Answers Guide for Biology Students

Earthworms are fascinating creatures that play a crucial role in our ecosystem. As biology students, dissecting an earthworm can be a valuable learning experience, providing a hands-on understanding of its internal anatomy. In this guide, we will walk you through the steps of an earthworm dissection and provide answers to common worksheet questions.

Materials Needed

• Earthworm (preferably Lumbricus terrestris)
• Dissection tray
• Scalpel or dissection scissors
• Forceps
• Magnifying glass or microscope
• Worksheet with questions

Step-by-Step Dissection Guide

1. Observing the External Anatomy
   • Start by observing the external anatomy of the earthworm. Note the segmented body, setae (bristles), and the clitellum (a glandular section used for reproduction).
   • Record your observations in the worksheet.
2. Making the Incision
   • Hold the earthworm firmly in place with forceps and make a shallow incision along the dorsal (top) side of the body, starting from the pharynx (throat) to the anus.
   • Cut carefully to avoid damaging the internal organs.
3. Exposing the Internal Organs
   • Use forceps to gently pry open the incision and expose the internal organs.
   • Observe the pharynx, esophagus, crop, gizzard, and intestine.
4. Identifying the Digestive System
   • Locate the mouth and pharynx. Note the muscular structure of the pharynx.
   • Identify the esophagus, which connects the pharynx to the crop.
   • Find the crop, a sac-like structure used for food storage.
   • Observe the gizzard, a muscular organ used for grinding food.
   • Note the intestine, a long, thin tube where nutrient absorption occurs.
5. Examining the Circulatory System
   • Locate the five paired aortic arches, which pump blood to the rest of the body.
   • Identify the dorsal blood vessel, which runs along the dorsal side of the body.
   • Note the ventral blood vessel, which runs along the ventral (bottom) side of the body.
6. Observing the Nervous System
   • Locate the cerebral ganglion (brain) at the anterior (front) end of the earthworm.
   • Identify the ventral nerve cord, which runs along the ventral side of the body.

Worksheet Answers

1. What is the function of the setae (bristles) on the earthworm’s body?
   • Answer: The setae help the earthworm move and burrow into the soil.
2. What is the name of the glandular section used for reproduction?
   • Answer: Clitellum.
3. What is the function of the pharynx?
   • Answer: The pharynx is a muscular structure that helps move food into the esophagus.
4. What is the function of the gizzard?
   • Answer: The gizzard is a muscular organ that grinds food into smaller particles.
5. What is the function of the five paired aortic arches?
   • Answer: The aortic arches pump blood to the rest of the body.
6. What is the function of the ventral nerve cord?
   • Answer: The ventral nerve cord transmits signals from the brain to the rest of the body.

🔍 Note: Make sure to handle the earthworm gently and humanely during the dissection process. If you are unsure about any part of the dissection, consult with your instructor or a teaching assistant.

Conclusion

Dissecting an earthworm can be a valuable learning experience for biology students. By following this guide and answering the worksheet questions, you should now have a better understanding of the earthworm’s internal anatomy and its various systems. Remember to always handle the earthworm gently and humanely during the dissection process.

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