Earthworms & More

Earthworm Dissection PreAP Biology March 11, 2014- GABI MATA

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Lumbricus terrestris

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, has a closed blood circulatory system, has a central and a peripheral nervous system, and contains muscles along each of its outer segments and in its guts to digest food. These animals are invertebrates, mainly are herbivores as it eats of decomposed plants (even if they decompose, they do not rely on decomposition for nutrients but rather plants), live up to six years, and are relatively the size of a tea cup. Humans, snakes, birds, rodents, and a number of insects all are known predators to the earthworm. Earthworms share many common adaptations such as their streamlined body shape, their setae (bristly hairs used to help the earthworm move through the soil), their ability to secrete mucus, and their capability to sense vibrations. However, with each different species of earthworm, there are different adaptations they have depending on their location.

Get To Know Your Earthworm!

Today's Objectives

Students will be learning about the external and internal anatomy of an earthworm. Students will focus on the organs, structures, and functions of the earthworm's body system, specifically digestive or circulatory. Students will also study the ecological roles of an earthworm, as well as the earthworm in general.

Earthworm's Reproductive Life Cycle

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Earthworm Dissection 101

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Internal Anatomy:

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Digging into the Digestive System

An earthworm’s digestive system works as a large, single unit with individual parts that each maintain their own certain and unique function. Each of these parts, consisting of the pharynx, the esophagus, the crop, the intestine, and the gizzard, are separated into many different regions and each perform a different function to benefit the earthworm. The system begins when the earthworm intakes food from the soil through its mouth and is then swallowed by its pharynx. The food will then pass through into its esophagus, where special glands will release calcium carbonate to rid the earthworm’s body of any excess. Following the path of the digestive tract, it will then pass through into the crop, where it will be stored for later use. When released from the crop, it will move into the gizzard, where special stones the earthworm ate will help grind the food down. Once completely broken down, the food will head into the intestines. Gland cells within the intestines will then aid in the digestive process. The intestinal walls contain special blood vessels that function to absorb and transport the nutrients from the digested food to the rest of the earthworm’s body or, if not useful to the earthworm, will then be excreted out its anus in small balls known as casts, which withhold bacteria needed for plants to cycle nutrients.

Get to Know the Digestive System Even Better