Everything about Earthworms

Earthworm Dissection Ella Hawes April 9, 2014 PAP Bio- Vu- 7

Lumbricus terrestris

Earthworms are classified under the kingdom Animalia, the phylum Annelida, the class Oligochaeta, the order Opisthopora, the family Lumbricidae, the genus Lumbricus, and the species terrestris. Earthworms are segmented worms with bilateral symmetry. Earth worms are hermaphrodites, which means that each earthworm has both sperm and egg. Earthworms burrow in soil to obtain nutrients and fertilize the soil.

Today's Objectives

Today, viewers will be learning all about earthworms and their anatomy. This presentation focuses on the the earthworm's digestive system, including the organs, functions, and structures.

Background Information: Life Cycle

Lumbricus terrestris otherwise known as an earthworm, has an interesting life cycle. Before earthworms are born they are held in a protective cocoon. The hatchilings leave their cacoon and burrow into the soil. Once in the soil, they can mature to adult earth earthworms. Adult earthworms are hermaphrodytes, meaning they have both male and female reproductive organs. Earthworms will exchange sperm with one another and fertilize eachothers eggs. The cacoon will form on each of the worms clitellum and will hatch. Then the cycle repeats. Below is a diagram displaying the earthworm's life cycle.

Background Information: Habitat

The most common habitat for an earthworm is in soil. Within this enviorment, earthworms have different niches, meaning its physical location and the role it plays within the environment. The three different niches earthworms fill is the compost and soil-surface dwellers (epigeic), topsoil dwellers (endogeic) and deep-burrowing subsoil dwellers (anecic). Also certain earthworms live in manure, mud, and decaying plants.

Background Information: Predators

Worm have many predator inculding snakes, birds, chipmunks, moles, rats, skunks, racoons, and a number of insects. Not only do animals kill earthworms but humans are one of the worms biggest predators because farmers kill many worms when they plow their fields and many chemicals in fertilizers are harmful to worms.

Background Infromation: Adaptions

Earthworms have many adaptions. One structural adaption is the earthworm's setae. These are bristly hairs that help the worm better grip the soil. Also, when the soil becomes too hot an earthworm will move deeper into the soil, coil into a tight ball, excrete a protective mucus and lower their metabolic rate in order to reduce water loss. This process is called aestivation.

Dissection pictures

Dissection

Before the digestive system is discussed in detail, here is an earthworm dissection tutorial that discusses the entire earthworm's anatomy.
Earthworm Anatomy

Dissection: The Digestive System

The digestive system in an earthworm consists of a mouth, pharynx, esophagus, crop, gizzard and intestine. The function of the mouth is an entry place for food. The pharynx's function is recieve the food from the mouth and lubricate it with mucus. Then the food is passed to the esophagus which uses calcium carbonate to neutralize acids. Next, the food goes to the crop which mixes and temporarily stores the food. This then enters the gizzard which is where the main digestive action takes place. The gizzard churns and mixes the mass of food and dirt. Finally, this mixutre is sent to the intestine where a helpful bacteria eats the food and releases many vitamins.

Extra Information

A few fun facts about earthworms include:

-Eathworms do not have eyes.

-There are about 2,700 different kinds of earthworms.

-In one acre of land, there can be more than 1 million worms.

-The largest earthworm ever found was found in South Africa and measured 22 feet.