CLASSIFICATION OF KINGDOM ANIMALIA
https://en.wikipedia.org/wiki/Animal
The Kingdom Animalia is broadly divided
into different phyla. One of the
most primitive phyla is:
1- Phylum Porifera
General Characteristics
The organisms in Phylum Porifera are commonly known as sponges.
Most sponges are marine, while some inhabit freshwater.
Examples:
- Leucosolenia (marine)
- Euplectella (*Venus' flower basket*) –
marine Venus is the Roman goddess of love and beauty.
The sponge’s
graceful, glassy appearance reminded early naturalists of something beautiful
and artistic—worthy of being associated with Venus.
Hence, it was
named “Venus’ Flower Basket” to reflect both its aesthetic beauty and symbolic
value.
- Spongilla – a common freshwater sponge
Body Organization
Sponges do not
have a tissue level of organization.
Most are asymmetrical, though some show radial symmetry.
They lack a nervous system.
Body Structure
The body wall
contains numerous tiny pores called ostia
through which water enters.
Water exits the
body through a larger opening called the osculum.
Body Layers
1. Outer Layer:
- Composed of thin, flat cells called pinacocytes.
2. Middle Layer:
- Jelly-like layer known as mesohyle.
- Contains mobile amoeboid cells.
3. Inner Layer:
- Lines the central cavity (spongocoel).
- Made up of choanocytes or collar cells.
Skeletal System
The skeleton is made up of tiny needle-like
structures composed of calcium carbonate
or silica.
Reproduction
Most sponges
reproduce asexually:
- Common methods
include budding and regeneration.
Some sponges
produce gemmules, which are
resistant capsules:
- When the parent
sponge dies, it releases gemmules.
- In favorable
conditions, amoeboid cells emerge
from gemmules to form a new sponge.
Commercial Use
A commercial sponge is prepared by drying, beating, and washing a
sponge until all its cells are
removed, leaving behind the skeleton.
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