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Questions and Answers
What characteristic distinguishes Annelida from other phyla mentioned?
What characteristic distinguishes Annelida from other phyla mentioned?
Which term best describes the body structure of Annelida?
Which term best describes the body structure of Annelida?
What type of organism is included in the Phylum Annelida?
What type of organism is included in the Phylum Annelida?
Which group of organisms does NOT belong to the Annelida phylum?
Which group of organisms does NOT belong to the Annelida phylum?
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What is the primary habitat for members of the Phylum Annelida?
What is the primary habitat for members of the Phylum Annelida?
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Which classification correctly represents the relationship between metazoa and annelids?
Which classification correctly represents the relationship between metazoa and annelids?
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How many species are estimated to be present in the Phylum Annelida?
How many species are estimated to be present in the Phylum Annelida?
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Study Notes
Phylum Annelida
- Also known as "little ring"
- Segmented worms
- 15,000 species
- Found in marine, freshwater, and terrestrial environments
- Include marine worms, freshwater worms, terrestrial worms, and leeches
- Worldwide distribution
- Soft bodies
- Size varies from less than 1mm to many meters
Annelida Characteristics
- Bilaterally symmetrical and triploblastic
- Segmented body composed of metameres (metamerically segmented)
- Eucoelomate: Have a true coelom lined by mesoderm. The coelom is located between the body wall and intestine, filled with fluid that acts as a buffer allowing for movement without pressure on the intestine.
Annelida Body Wall
- Integument: A single cell layer epidermis with mucous glands that secrete a moist cuticle (for protection and movement)
- Muscles: Outer circular and inner longitudinal muscle layers. Each segment has independent muscles.
- Respiration: Occurs through skin, parapodia, and gills (in some)
Annelida Circulatory System
- Closed circulatory system with blood vessels that run the length of the body and branch into each segment.
- Blood contains hemoglobin, increasing oxygen carrying ability.
- Some have 5 pairs of hearts that pump blood.
Annelida Digestive System
- Specialized digestive tract with mouth, pharynx, esophagus, crop, gizzard, and intestine.
- Gizzard contains sand grains for grinding.
- Calciferous glands remove calcium and carbonate ions.
- Typhlosole is a dorsal longitudinal fold that increases the surface area of the intestine for absorption.
Annelida Nervous System
- Paired ventral nerve cord
- Ganglia (masses of nerve cell bodies) near the head act as a primitive brain.
- Ganglia send out segmental nerves per segment.
Annelida Excretion
- Excretion through nephridia (one pair per metamere)
- Nephridia act like kidneys; filter waste products from the coelomic cavity and release them through excretory pores.
Annelida Reproduction
- Hermaphroditic (containing both male and female reproductive organs).
- Sperm and eggs are deposited in a cocoon secreted by the clitellum (saddle-like swelling).
- External fertilization occurs within the cocoon.
- Embryo development occurs within the cocoon.
- No larval form in oligochaetes
Classes of Annelida
- Class Polychaeta ("many hairs")
- Mostly marine
- Well-developed head, segments, and parapodia (paddle-like appendages with chaetae for locomotion and gills
- Class Oligochaeta ("few hairs")
- Primarily terrestrial and freshwater
- Reduced head
- Few setae
- Have a clitellum
- Class Hirudinea (leeches)
- Primarily freshwater, some marine or terrestrial
- Lack appendages and setae
- Have suckers (for attachment)
- Some are carnivores; others are temporary or permanent parasites
- Clitellum is present only during reproduction
Medical Importance of Annelida
- Leech saliva contains antiseptic chemicals and anticoagulants (hirudin).
- Used in reconstructive surgery to promote blood circulation.
Earthworm
- A type of oligochaete
- Features include segmented body, cuticle, circular and longitudinal muscles, and digestive system (with crop, gizzard, and intestine)
- Have a closed circulatory system and excretory organs (nephridia)
- Hermaphroditic and reproduce via external fertilization in a cocoon.
- Have a well-developed head with a ventral nerve cord.
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Description
Explore the fascinating world of Phylum Annelida, commonly known as segmented worms. This quiz covers their characteristics, body structure, and various species found in different environments. Test your knowledge on their unique features, including respiration and circulatory systems.
