Animal Classification

Topics: Annelid, Phylum, Cnidaria Pages: 33 (6120 words) Published: May 31, 2011


Phylum Porifera
(GK: Porous = Pores + Ferro = form)

Main characters:
1. They are commonly called as sponges.
2. They are sessile animals.
3. Sponges range in height from about 1cm to 2cm.
4. More than 5000 species of sponges are found.
5. All are marine, while some are fresh water.
6. The central body cavity is called spongocoel.
7. A single large opening is called as osculum.
8. They are filter feeders.
9. Body lining is formed by flagellated cells called choanocytes or collar cells. 10. They are diploblastic and porous, pores called ostia.
11. They layers of body are separated by a gelatinous region called the mesophyl. 12. Gametes arise from ameobocytes.
13. Pores are made up of porocytes.
14. Internal skeleton is made up of spicules.
15. These spiculles are made up of silicon, calcium carbonate or a protein called sponging. 16. Most sponges are hermaphrodites.
17. Cross-fertilization is found.
18. Asexual reproduction occurs by fragmentation and gemmule formation. 19. Fertilization occurs in the mesohyl.
20. Regeneration is also found.
21. Sponges have no nerves or muscles.
Examples: Sycon, Leucosolenia, Spongilla.

Classes of phylum porifera
Following are the main classes of Phylum Porifera:
1. Class:Calcaria
2. Class:Hexactinellida
3. Class:Demospongia

1. Class: Calcaria Main characters:
1. They are simple sponges.
2. The spicules are calcareous.
3. They are marine and fresh water.
4. They are non-motile.
5. Body is elongated.
Example: Sycon, Leucosolenia

2. Class: Hexactinellida

Main Characters:
1. These are glass sponges.
2. The spicules are siliceous.
3. These spicules are united in net or separate form.
4. They are elongated shaped.
Example: Euplectella (Venus’s Flower-basket)

3. Class: Demospongia

Main Characters:
1. They are bath sponges.
2. They do not posses spicules.
3. If spicules are found, they are made up of silicon or sponging fibers or both. 4. They are spherical shape.
5. They are also found in Fresh water.
Examples: Spongilla, Euspongia.

Phylum Coelenterata
(GK. Koitos = Cavity + Enteron = Intestine)

Main Characters:
1. They are simple, multicellular and diplobastic but mesogloea is also found. 2. They are mostly marine.
3. More than 9000 living species are found.
4. They poses a central digestive cavity called as gastrovascular cavity or also called as gastrocoel. 5. A single opening is present which functions as both mouth and anus. 6. They are solitary or colonial.

7. They are also called cnidaria (GK. Cnide = nettle).
8. They are radial symmetrical.
9. Reproduction takes place by budding.
10. Circulatory, respiratory, excretory, and various other systems are absent. 11. Nervous system consists of nerve net.
12. Alternation of generation is also found.
13. They posses two forms, polyp and medusa.
14. Polyps are cylindrical forms like hydra and sea-anemones. 15. Medusa is umberella shaped, like Jelly-fish.
16. Polyps are sessils and medusa is free-swimming.
17. They are carnivorous.
18. Mouth is surrounded by tentacles.
19. Tentacles posses unique cells called as cnidocytes.
20. These cnidocytes contains stinging cells called as nematocytes. 21. Tentacles are used for defence and prey.
22. They have no brain.
Example: Hydra, Jelly-Fish, Sea-Anemone.

polyp Medusa

Life-cycle of Obelia

Classes of phylum coelenterata
Following are the main classes of Phylum Coelenterata:
1. Class:Hydrozoa
2. Class:Scyphozoa
3. Class:Anthozoa

1. Class: Hydrozoa

Main Characters:
1. They are marine and fresh water.
2. They are solitary or colonial.
3. They are sessile or free-swimming.
4. They exhibit polymorphism.
5. They are found in polyp form as well as in medusa form.
Examples: Hydra, Obelia, Physalia....
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