Phylum Annelida is very segmented and symmetrical compared to phylum Cnidaria and Porifera. Each ring on the earthworm is a segment. We made an incision along the ventral side to expose the internal organs. Once cut open, it was very easy to identify the heart, seminal vessel, septum, and intestine. Earthworms have bilateral symmetry. Like squids, earthworms have the presence of organs.
Flatworms are soft, flattened worms that have tissues and internal organ systems. They are the simplest animals to have three embryonic germ layers, bilateral symmetry, and cephalization.
Groups of Annelids: Oligochaetes are annelids that typically have streamlined bodies and relatively few setae compared to polychaetes. Most oligachaetes live in soil or fresh water. Leeches are typically external parasites that suck the blood and body fluids of their host. Polychaetes are marine annelids that have paired, paddlelike appendages tipped with setae.
Ecology:
Earthworms were called "the intestines of the earth" by Aristotle. Their tunnels provide passage ways for plant roots and water and allow the growth of beneficial, oxygen-requiring soil bacteria. Annelids also participate in a wide range of food chains in the sea.
Flatworms are soft, flattened worms that have tissues and internal organ systems. They are the simplest animals to have three embryonic germ layers, bilateral symmetry, and cephalization.
Groups of Annelids: Oligochaetes are annelids that typically have streamlined bodies and relatively few setae compared to polychaetes. Most oligachaetes live in soil or fresh water. Leeches are typically external parasites that suck the blood and body fluids of their host. Polychaetes are marine annelids that have paired, paddlelike appendages tipped with setae.
Ecology:
Earthworms were called "the intestines of the earth" by Aristotle. Their tunnels provide passage ways for plant roots and water and allow the growth of beneficial, oxygen-requiring soil bacteria. Annelids also participate in a wide range of food chains in the sea.