Segmented Worms

Segmented Worms

Introduction
Segmented worms are special because they can do so much stuff with no arms or legs. They can move without legs. Examples of Segmented Worms are: earthworms, marine worms and leeches. Actually, the more numerous and typical members of the phylum are marine, crawling or hiding under rocks, or living in burrows, or in tubes, or in the sediment. Now I willtell you more information about segmented worms. I hope that we will learn interesting things through this project.
Segmented Worms Characteristics
Segmented worms (phylum Annelids) are so named because of their elongated, more or less cylindrical bodies divided by grooves into a series of ring-like segments. Each segment contains nerve cells and waste-secreting organs. The digestive tractis not segmented. It is instead a continuous, through and through tube that runs through all segment walls. Just like the digestive tract, the nerve cord and the two main blood vessels are also continuous. Each body segment has some small blood vessels that connect to the two main blood vessels. These worms have a closed circulatory system. Segmented worms are bilaterally symmetrical (if youcut an earthworm along its vertical plane, the two resulting halves are identical to each other).
Segmented Worms Habitat
Segmented worms can be found in fresh and salt water. Earthworms can be found at just about every corner of the earth. They live in trees, bark, and under rocks, and along rivers, near springs, and near ponds. Their favorite place to live, however, is in the earth’srich soil. During the winter months they burrow deep within the earth until the surface warms again during the spring. During the warm summer months worms stay closer to the tops of soil where they create tunnels to wiggle in and out of. These tunnels are extremely important for plant life as they create a path for water and air, which is essential for the survival of plant life.
Earthworms BodySystems
Earthworms have a definite front end and backend. They have more than 100 body segments. Earthworms on the outside of each body segment have a bristle-like structure called setae. Each body segment has four pairs of setae (except for the first and last segments). They use their setae to hold on to the soil and to move. The setae, made of a substance called chitin, are used incrawling or in swimming. They have bilateral symmetry. Their body is composed of: body cavity that holds the organ and two body openings: mouth and anus.
Digestion and Excretion
Earthworms get energy from the bits of leaves and other matter found in the soil. The soil ingested moves to the crop (sac used for storage). Then the gizzard (muscular structure behind the crop) grinds soil and thebite of organic material. Ground material passes to the intestine where the organic matter is broken down and the nutrients are absorbed by the blood. Wastes leave the worm through the anus.

How earthworms help fertilize the soil
Earthworms take in soil and provide spaces for air and water to flow through it. They provide and mix the soil. Their wastes pile up at the openings totheir burrows. The pile up is called casting (vermicompost), which helps fertilize the soil.
Earthworms Circulatory System
Earthworms have a closed circulatory system. Two blood vessels along the top of the body and one along the bottom of the body meet in the front end of the earthworm. There they connect to heart like structure called aortic arches. Aortic arches pump blood through thebody.
Earthworms Respiratory System
Earthworms do not have gills or lungs. Oxygen and carbon dioxide are exchanged through their skin. This means, they breathe through their skin, so the worm’s environment and the worm’s skin must be moist at all times. This allows the worm to breathe in oxygen. While the sand may be moist and wet closer the water, the majority of the sand is dry. If...