about the phylum of Cnidaria?

Question

Is Cnidaria the most primitive phylum on earth???
thanx guys :)

Answer 1

Cnidarians contain 2 body shapes: The polyp which is a cylindrical structure with tentacles at the top of the animal. The medusa is an umbrella shaped structure with its tentacles near the bottom of the animal.
They contain tentacles with special stinging cells called nematocysts. These nematocysts come in a variety of structures. They are activated by touch and can only be used once. They function in protecting the animal and helping capture its food. The cnidocytes are the cells that produce the nematocysts.
They contain 2 cell layers: the ectoderm or outer cell layer and the endoderm the inner cell layer.
These 2 layers are separated by a jelly-like layer called the mesoglea.
Within the mesoglea we find a nerve net. These organisms do not contain a brain. .
They contain a central cavity called the Gastrovascular cavity. Digestion takes place here and the contents are absorbed by the endodermal cells. The undigested food is expelled through its mouth. This is considered a two way digestive process.
They contain radial symmetry. Some organisms are sessile while others are free floating.
They reproduce by budding and regeneration. They also reproduce sexually. They contain both male and female reproductive structures in the same body. They are neither male or female, they are called hermaphroditic.
Many of these organisms are marine though some ( Hydra) are fresh water . The Sponge (Porifera) lack many of the above characteristics making them the most primitive animal phylum.

Answer 2

No, it's not even the most primitive phylum of animals. That would be the sponges in Phylum Porifera. But there are several kingdoms that arose before the animal kingdom. Start with bacteria.

Answer 3

If you are talking about the Animal Kingdom, then the most primitive would be Phylum Porifera, the sponges. These are the most primitive of the eukaryotes of the Animal Kingdom.

In Kingdom Plantae, the most primitive eukaryotes would be the algaes, the phytoplankton.

If you are talking about overall, then Kingdom Monera, the bacteria, would be the most primitive. These organisms are prokaryotes (lack membrane-bound nucleii and organelles).

BIOLOGY TEACHER

Answer 4

Sponges (Porifera) are generally considered to be the most primitive phylum of animals.