ANIMAL KINGDOM/Phylum-Coelenterata(Non-Chordates)

In this video it is discussed about the second phylum of non-chordates.
Phylum: Coelenterata
Characteristics:
1. Coelenterates are mostly marine except hydra(fresh water).
2. These are sessile or free swimming and solitary or colonial.
3. They exhibit radial symmentry and have tissue cell organisation.
4. They are acoelomates but do have cavity( coelentron) which acts as gastrovascular cavity.
5. Body is diploblastic with two layers: outer layer: Epidermis and inner layer: Gastrodermis
with a gelatineous mesoglea in between.
6. They exhibit special cells (Cnidoblast) in the outer epidermis and on tentacles which serve for food capture,adhesion and defence.
7. Nutrition is holozoic and digestion is intracellular as well extracellular.
8. Respiration and Excretion takes place through body surface.
9. They shows two types of forms: attached polyp and free-swimming medusa.
10. Nervous system is primitive in diffused form.
11. Reproduction: Asexual reproduction by exogenous budding and sexual reproduction by formation of gametes.
12. They exhibit both direct development and indirect development.
Classification:
They are categorised in three classes:
1. Class: Hydrozoa( Hydra)
2. Class: Scyphozoa( Aurelia)
3. Class: Anthozoa( Adamsia)