Annelid (earthworm) Dissection

Last Friday on November 30th our Biology class got to dissect earthworms. Between each pair we got one worm and we had to pin it down and carefully slice it open so we could investigate the parts inside. Having us observe the inside of real earthworms was an interactive and exciting way for us to learn more about how the digestive, nervous, circulatory and reproductive systems work and what they really look like. After doing this dissection I found that I had a better understanding of segmented worms and it was a good learning tool in addition to the information we had learned in class. In class we had learned about the different parts of the digestive system such as the mouth, the esophagus, the pharynx, the crop, the gizzard, the intestine and the anus. When we opened up the worm we were able to see all of these parts and the track that the food and soil it ate would travel. We had also learned about it's circulatory system in class. We found out that they have five "hearts" or pairs of aortic arches and these we found inside the body as well. In our notes we learned the biological role of earthworms and how they are composters that help turn organic matter into fertile soil. When we opened the worm my partner and I opened up the intestine and we could see the soil that was travelling towards the anus and being turned into a fertilizer. At first I found cutting open an earthworm a little bit gross but seeing all the knowledge we had learned happening inside this body really helped me understand the information more.

1. The pumping organs of an earthworm are pairs of aortic arches, or hearts.

2. The earthworms food enters through the mouth, goes into the pharynx, enters the area between the pharynx and the crop which is called the esophagus, then it enters the crop where the food is stored for a little while, next it is broken up in the gizzard, then it goes through the intestine where it's body absorbs the nutrients and lastly the waste passes through the anus.

3. There is one pair of ganglia above the pharynx which act as the brain of the earthworm and are connected to the rest of the body by the ventral nerve chord.






4. The two parts of the earthworms excretory system that we saw were the nephridia and the anus.




5. To find out if an earthworm eats soil you can open up the intestine and see what is inside of it.





6. The setae help with the earthworm's movement through their dirt environment. Without the setae they wouldn't be able to move very well.



7. The earthworm's digestive system is able to absorb all the nutrients from the food it eats and turn the soil and other waste into a fertilizer.


8. If we were to dissect the earthworm to the posterior end we would have seen the remainder of the intestine, the anus, the rest of the ventral nerve chord and some of the nerves coming off of it.





9. Earthworms are hermaphroditic, they contain both eggs and sperm. When they are ready to be released from the body the eggs exit through the female genital pores and e sperm go through the male genital pores. Each worm has a clitellum which protects the eggs in a cocoon structure. When an earthworm wants to reproduce they attach to another worm and exchange sperm, which travels into the seminal receptacles of its mate

Overall, we were able to find organs from the reproductive, digestive, nervous and circulatory system. Seeing all these systems for real put all the facts we had learned about earthworms into an accurate.