What part of the digestive system would you see in a cross-section anterior to the gizzard? The earthworm digestive system is divided up into four sections: ingestion, digestion, absorption, and excretion. Each section has a specific function that helps the earthworm survive. The ingestion is for sucking food as they make their way through the dirt. The digestion breaks down the food into smaller pieces that will be absorbed into the circulatory system. The absorption happens after the food is broken down and the nutrients enter into the circulatory system, it is then distributed into individual cells. Last is the excretion, which is when the earthworm gets rid of waste. The mouth, pharynx, and crop are located right before the gizzard, so these organs would be at the cross-section anterior. The mouth is where the food enters the body, the pharynx sucks the food into the mouth and the crop temporarily stores food. This would be part of the ingestion and digestion process.

What structure in the earthworm has a similar function as the human heart? Explain your answer. There are three main vessels that supply the blood to organs within the earthworm. These vessels are the aortic arches, dorsal blood vessels, and ventral blood vessels. The aortic arches function like a human heart. There are five pairs of aortic arches, which have the responsibility of pumping blood into the dorsal and ventral blood vessels. The dorsal blood vessels are responsible for carrying blood to the front of the earthworm’s body. The ventral blood vessels are responsible for carrying blood to the back of the earthworm’s body.

What do two earthworms exchange during mating? Explain your answer. Earthworms are hermaphrodites where each earthworm contains both male and female sex organs. The male and female sex organs can produce sperm and egg respectively in each earthworm. Although earthworms are hermaphrodites, most need a mate to reproduce. During mating, two worms line up inverted from each other so sperm can be exchanged. The earthworms each have two male openings and two sperm receptacles, which take in the sperm from another mate. The earthworms have a pair of ovaries that produce eggs. The clitellum will form a slime tube around it, which will fill with an albuminous fluid. The earthworm will move forward out of the slime tube. As the earthworm passes through the slime tube, the tube will pass over the female pore picking up eggs. The tube will continue to move down the earthworm and pass over the male pore called the spermatheca which has the stored sperm called the spermatozoa. The eggs will fertilize and the slime tube will close off as the worm moves completely out of the tube. The slime tube will form an “egg cocoon” and be put into the soil. The fertilized eggs will develop and become young worms.

Describe the difference between a closed and an open circulatory system.
In the closed circulatory system, blood is directed through arteries to veins throughout the body. The blood remains in vessels and is transported at high pressures to all extremities of the body at a rapid rate. In the open circulatory system, the heart pumps blood into open cavities, where blood vessels carry the blood throughout the body at a low pressure. There are two major differences between the open and closed system. First, the open system bathes all organs and tissues throughout the body with blood and, second, there are no arteries or major veins to increase blood pressure and direct distribution.

Do earthworms have a front and a back end? Explain your answer.
Yes, the earthworm has both an anterior (front) and a posterior (rear). The mouth and brain are located in the anterior, with the anus located in the posterior.

What characteristics distinguish an annelid from other worms?
Annelids are worms whose bodies are divided into segments, arranged in linear series and externally marked by circular rings called annuli. They also have tiny bristles called setae that cover their bodies.