An Earthworm Tale

Earthworm dissection Pre-Ap Biology April 7, 2014 - Guzman

The Birth of a Beautiful Lumbricina

Lumbricina (simply known as "earthworms") are an order of Haplotaxida. They belong to the kingdom Animalia which is under the phylum Annelida and subphylum Oligochaeta. An earthworm is a tube-shaped, segmented animal commonly found living in soil, that feeds on live and dead organic matter. Its digestive system runs through the length of its body. It conducts respiration through its skin. An earthworm has a double transport system composed of coelomic fluid that moves within the fluid-filled coelom and a simple, closed blood circulatory system. It has a central and a peripheral nervous system. The central nervous system consists of two ganglia above the mouth, one on either side, connected to a nerve cord running back along its length to motor neurons and sensory cells in each segment. Large numbers of chemoreceptors are concentrated near its mouth.

Learning At The Objective System

Students will be learning about the external and internal anatomy of an earthworm. Students will also learn about the organs, structures, and functions of the circulatory system. Students will also understand the ecological role of this majestic insect.

Benefits of an Earthworm:

The Home and Ecology of An Earthworm

The main habitat of earthworms is in soil, but it can also be a lot more complicated than that. Some live in decaying plant matter and manure, others are generally found in decaying conifer logs. Sometimes they are found in mud in streams. Some species are arboreal, some aquatic and some euryhaline and littoral.

Earthworms form the base of many food chains. They are preyed upon by many species of birds, snakes, mammals, and invertebrates. Various species of worms are used in vermiculture, the practice of feeding organic waste to earthworms to decompose food waste.

Earthworm populations depend on both physical and chemical properties of the soil, such as temperature, moisture, pH, salts, aeration, and texture, as well as available food, and the ability of the species to reproduce and disperse. One of the most important environmental factors is pH, but earthworms vary in their preferences. Most favor neutral to slightly acidic soils.

The Lovely Heart of an Earthworm

The earthworm has a dual circulatory system in which both the coelomaic fluid and a closed circulatory system carry the food, waste, and respiratory gasses. The closed circulatory system has five main blood vessels: the dorsal vessel, which runs above the digestive tract; the ventral vessel, which runs below the digestive tract; the subneural vessel, which runs below the ventral nerve cord; and two lateroneural vessels on either side of the nerve cord. The dorsal vessel moves the blood forward, while the other four longitudinal vessels carry the blood to the rear. A pair of aortic arches rings the coelom and acts as hearts, pumping the blood to the ventral vessel that acts as the aorta. The blood consists of ameboid cells and hemoglobin dissolved in the plasma. The second circulatory system derives from the cells of the digestive system that line the coelom. As the digestive cells become full, they release non-living cells of fat into the fluid-filled coelom, where they float freely but can pass through the walls separating each segment, moving food to other parts and assisting in wound healing.

Fun Facts About Earthworms!

Try Out An Earthworm Dissection!