Practice: Understanding Earthworms by Emily Amodei

Understanding Earthworms

ms_amodei1 — 2024-02-16 12:52:07 UTC

The term Earthworm refers to a specific group of invertebrates within the taxonomic phylum Annelida. Earthworms belong to the Oligochaetes, which means "few bristles." Worldwide there are over 5,000 species. Earthworms, as their name suggests, are terrestrial, their skin is permeable and they need a moist environment so they don't dry out. Earthworms are greatly beneficial to the enviornment. Their ability to enrich soil has advantages for plants, animals, and humans. Earthworms eat organic matter such as leaves and roots. Once digested, the earthworm releases a casting that contains nutrients that help plants grow. Plants cannot use directly use organic matter; therefore, they rely on the earthworm castings as a form of natural fertilizer.

Segmented Body

ms_amodei1 — 2024-02-16 12:52:21 UTC

Earthworms are classified in the phylum Annelida or Annelids, which in Latin means, “little rings.” The body of the earthworm is segmented which looks like many little rings joined together. The earthworm is made of about 100-150 segments. The segmented body parts provide important structural functions. Segmentation can help the earthworm move. Each segment or section has muscles and bristles called setae. These bristles help control the worm when moving through soil. The bristles hold a section of the worm firmly into the ground while the other part of the body protrudes forward. Segmentation helps the worm to be flexible and strong in its movement. If each segment moved together without being independent, the earthworm would be stationary.

Digestive System

ms_amodei1 — 2024-02-16 12:52:36 UTC

The digestive system is partitioned into many regions, each with a certain function. The digestive system consists of the pharynx, esophagus, crop, intestine and gizzard. Food such as soil enters the earthworm’s mouth where it is swallowed by the pharynx. Then the soil passes through the esophagus, which has glands that release calcium carbonate to rid the earthworm’s body of excess calcium. 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 grinds up the food completely. The food moves into the intestines as 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.

Respiratory System

ms_amodei1 — 2024-02-16 12:53:10 UTC

Earthworms do not have lungs. They breathe through their skin. Oxygen and carbon dioxide pass through the earthworm’s skin by diffusion. For diffusion to occur, the earthworm’s skin must be kept moist. Body fluid and mucous is released to keep its skin moist. Earthworms, therefore, need to be in damp or moist soil. This is one reason why they usually surface at night when it is possibly cooler. Earthworms have developed the ability to detect light even though they cannot physically see. They do so using tissue located at the earthworm’s head that is sensitive to light. These tissues enable an earthworm to detect light and not surface during the daytime where they could be affected by the sun.

Circulatory System

ms_amodei1 — 2024-02-16 12:53:23 UTC

Another important organ system is the circulatory system. The earthworm has a closed circulatory system. An earthworm circulates blood exclusively through vessels. 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.

Reproduction

ms_amodei1 — 2024-02-16 12:53:43 UTC

Earthworms contains both male and female sex organs. The male and female sex organs can produce sperm and egg respectively in each earthworm. Though the use of the clitellum, the earthworm can exchange sperm which will unite with egg to form offspring.

ms_amodei1 — 2024-02-16 13:20:34 UTC

ms_amodei1 — 2024-02-16 13:21:35 UTC

ms_amodei1 — 2024-02-16 13:25:24 UTC

ms_amodei1 — 2024-02-16 13:25:51 UTC

ms_amodei1 — 2024-02-16 13:27:10 UTC

ms_amodei1 — 2024-02-16 13:27:44 UTC

ms_amodei1 — 2024-02-16 13:27:54 UTC

ms_amodei1 — 2024-02-16 13:28:18 UTC