Table of Contents
How many annelids exist?
A major invertebrate phylum of the animal kingdom, the annelids number more than 9,000 species distributed among three classes: the marine worms (Polychaeta), which are divided into free-moving and sedentary, or tube-dwelling, forms; the earthworms (Oligochaeta); and the leeches (Hirudinea).
How many classes of Annelida are there?
three
Most authors accept the annelids as having three major classes: Polychaeta, Oligochaeta, and Hirudinea.
Who named Annelida first?
CSS :: Phylum Annelida
| [A]. | Linnaeus | Lamarck |
|---|---|---|
| [C]. | Dales | Schwann |
Where are annelids found?
Introduction to Annelida and the Class Polychaeta They comprise the dominant invertebrates of the deep sea. Fresh or inland water annelids can be found in all kinds of aquatic and semi-aquatic environments, such as lakes, ponds, streams, rivers, groundwater, wet soils, and other wet habitats.
Do annelids have Cephalization?
Annelids have a nervous system made of two ventral cords and one relatively large nervous cell concentration at its anterior portion, which resembles a primitive brain. Therefore, cephalization in annelids is greater than in nematodes or in flatworms.
Do all polychaetes have parapodia?
The known species of polychaetes share only a few characteristics. Each has a head, a tail and a segmented body, and typically each body segment has a pair of leg-like parapodia with spiny bristles sticking out. Since there is an exception to every rule, some polychaetes have no parapodia at all.
What do annelids and mollusks have in common?
Like mollusks, however, they have a coelom. Annelids have other similarities with mollusks, including: A closed circulatory system (like cephalopods). An excretory system consisting of tubular nephridia.
Do mollusks have cephalization?
Mollusks represent another group in which cephalization has been lost and regained. For example, bivalves are not particularly cephalized (although some scientists have argued that they are “all head”). However, as with the echinoderms, certain mollusks regained cephalization.
How many pairs of legs do annelids have?
– They have 14-43 pairs of simple conical walking legs. These are not jointed or segmented but are instead saclike and contain coelomic fluid and external muscle insertions.