Reference

Discovery Communications, . (2000). All About Earthworms. Retrieved (2009, October 12) from http://yucky.discovery.com/flash/worm/pg000102.htm

Earthworms (2003). [Online], Available: www.kidcyber.com.au

Home Training Tools, . (2009). Earthworm Dissection.Home Science Tools. Retrieved (2009, October 12) from http://www.hometrainingtools.com/article.asp? ai=1319&bhcd2=1255394489

Sandhyarani, N. (2009). Earthworm Classification (Taxonomy). Buzzle.com. Retrieved (2009, October 12) from http://www.buzzle.com/articles/earthworm-classification- taxonomy.html

LaRosa, L. (n.d.). Earthworm Dissection. Retrieved from http://www.middleschoolscience.com/earthworm2.htm

Conclusion

Throughout this dissection we have learned various curiositys and the anatomy of the common earthworm. We have seen how they reproduce, their taxonomy, their anatomy, and their way of life. In addition we have learned how to properly dissect one of these animals and have gathered experience which will help us in future dissections. We have also viewed the impact that this relatively simple organism has on our environment and how its existence has helped other living beings, such as plants and birds, survive and prosper throughout the world.

Anatomy

List of the anatomical parts of the earthworm:

• somites or metameres- body segments
• pharynx- used as a tongue to gather food from the exterior and brought into the esophagus
• brain-control center of the worm
• aortic arches-"hearts" which compress to circulate blood around the worm, they consist of five pairs
• esophagus-transport food from the pharynx to the crop
• crop- stores food
• gizzard- breaks up food that is stored in the crop
• intestine- absorbs the nutrients needed for proper function
• dorsal/ventral blood vessels- circulate blood throughout the worm
• seminal vesicles- contain the male reproductive organs
• clitellum- collar used in reproduction
• mouth- used to acquire food
• anus- used to expel wastes
• setae- bristles in the ventral part of the worm used for movement

Dissection

The following dissection was done in order to learn how to do further dissections as well as to find the internal and external anatomy of the common earthworm.

In order to carry along a proper dissection of a earthworm, the following materials are needed:

• specimen
• dissection tray
• dissection kit
• gloves
• protective goggles
• apron

Here is the procedure to opening and viewing the specimen.

1. Place the worm ventral side down and, with dissecting pins, pin the worm down to assure minimum movement during the dissection
2. Take a scalpel and carefully begin opening the worm from the clitellum to the mouth
3. As you cut, pin down the skin and reveal the internal organs in the "head" of the worm
4. Once you have the anterior end open, you may proceed to open the posterior end of the worm
5. It is not necessary to open the posterior end of the worm completely, since it contains the same anatomy from the clitellum to the anus
6. Once the earthworm is completely open, proceed to identify all of the internal and external anatomical structures you can find and label them

Images:

lombricus terrestris

The earthworm,scientifically referred to as lumbricus terrestris, is a segmented animal which lives in all corners of the earth where there is soil for it to find its food, and humid enough to permit its respiration. It mainly feeds on plant matter, be it alive or decaying. Occasionally it eats insects and other small organisms. Earthworm excrements, also known as castings, enrich the soil with nutrients which promote healthy plant life. it is such an effective fertilizer, that humans have created earthworm farms in which they produce these castings and sell them to farmers as fertilizer.

Earthworms are hermaphroditic; meaning that they possess both male and female reproductive organs. However, reproduction takes place via cross-fertilization. During sexual intercourse each earthworm deposits gametes into the clitellum of the other worm. Some time after the gametes have entered the clitellum, the earthworm ejects the eggs mixed together with some of its gametes and places them in a cocoon that will protect future worms before they hatch. Earthworms have an approximated life expectancy of 6 years.

Taxonomy and Systems

1. The following is the taxonomy of the common earthworm:

1. Kingdom- Animalia: Eukaryotic, multicellular organisms which move and depend on dead plants for energy
2. Phylum- Annelida: Have segmented bodies (each segment is divided by a septum) and a closed circulatory system
3. Class- Clitellata: Have a clitellum(a type of collar which secretes a cocoon during reproduction)
4. Subclass- Oligocheta: Have setae, or bristles, which help them move about their environment
5. Order- Haplotaxida
6. Family- Lumbricidae:One of the largest earthworm families
7. Genus- Lumbricus
8. Species- Lumbricus terrestris: Go to the surface to find their food

Systems present in the earthworm:

• Nervous
• Muscular
• Circulatory
• Respiratory
• Digestive
• Reproductive

Introduction

Welcome to the blog for the dissection of the common earthworm. My name is Andrés Díaz and I am from El Colegio San Ignacio de Loyola; a high school in San Juan, Puerto Rico. In the following blog I will describe the procedure I went through to dissect a common earthworm (lumbricus terrestris).