WIGGLY WORMS

An Earthworm Dissection Lab By: Mariam Moini, Mitcham P2

Objectives

The purpose of the the earthworm dissection is to learn the internal and external anatomy of an earthworm.The veiwer will also take a closer look into the digestive system of the earthworm and understand what role the earthworm plays in the environment.

Background information on Earthworms

Scientific Name

The scientific name of the earthworm is the Lumbricina.


Taxonomy

•Kingdom: Animalia

•Phylum: Annelida

•Class: Clitellata

•Order: Haplotaxida

•Family: Lambricicdae

•Genus: Lumbricus

•Species: Terrestris


Prey/Predators

Earthworms get their nutrition from many forms of organic matter in soil, such as decaying roots and leaves, and living organisms such as nematodes, protozoans, rotifers, bacteria, and fungi. They will also feed on the decomposing remains of other animals. Snakes, birds, moles, toads and even foxes are known to eat earthworms. Beetles, centipedes, leeches, slugs and flatworms also feed on earthworms.


Habitat

Earthworms are found all over the world.Most live in muck and mud around freshwater, but some live under the sea, and many live in the soil on land.Moist soil conditions are needed in order for survival.Earthworms are usually found in places where there is moist soil and dead plant material. Earthworms are most abundant in rainy forest areas, but can be found in many habitats on land and in freshwater.


Fun Facts


  • Some earthworm species can live up 8 years, but it is very rare for them to survive that long. Most are eaten or killed in some other way before they live for one year.
  • Earthworms only communicate with each other by touch and taste, but they can feel vibrations, and often avoid predators by sensing their footsteps. They can also sense light and moisture in the air.
  • Earthworms' main defense is hiding in their burrows in the soil. They will quickly crawl down into the ground if they detect a predator.
  • There are approximately 2,700 different kinds of earthworms.

  • Even though worms don’t have eyes, they can sense light, especially at their anterior (front end). They move away from light and will become paralyzed if exposed to light for too long (approximately one hour)

Digestive system of an earthworm

The digestive system consists of the pharynx, the esophagus, the crop, the intestine and the gizzard.Food enters the earthworm’s mouth where it is swallowed by the pharynx. Then the soil passes through the esophagus, where the excess calcium is gotten rid of.After it passes through the esophagus, the food moves into the crop where it is stored and then eventually moves into the gizzard. The gizzard uses stones that the earthworm eats to grind the food completely. The food moves into the intestines as gland cells in the intestine release fluids to aid in the digestive process. The intestinal wall contains blood vessels where the digested food is absorbed and transported to the rest of the body.



  • Mouth – First part of the digestive system that takes in food
  • Pharynx –Food is lubricated after leaving the mouth for easier passage
  • Esophagus (5th to 7th segment) - Tube-like structure that leads food out to the crop
  • Crop – Stores food as it moves through the system. The food is mixed together in the crop and then passed to the gizzard for the actual process of digestion to begin.
  • Gizzard – Grinds and breaks apart food. There are enzymes secreted from the walls of the gizzard that help in the digestion, that is, chemical breakdown of the organic matter ingested. The thick paste so formed is then pushed into the intestine.
  • Intestine (15th to 120th segment) – Transports nutrients and soil through the digestive system. It contains bacteria that help in further breakdown of the food. The bacteria act on the food releasing vitamins, proteins, carbohydrates and minerals in the worm body to help it survive.
  • Anus – Opening where waste from digestion exits the body
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Earthworms Relationship to the Surrounding World

Earthworms play an important role in breaking down dead organic matter in a process known as decomposition.Decomposition releases nutrients locked up in dead plants and animals and makes them available for use by living plants. Earthworms do this by eating organic matter and breaking it down into smaller pieces allowing bacteria and fungi to feed on it and release the nutrients.Earthworms are also responsible for mixing soil layers and incorporating organic matter into the soil.