???? ???? ??????
???? ??? ?????? ?????????? ?? ??-

Hydra (genus)
From Wikipedia, the free encyclopedia
Jump to navigationJump to search
This article is about the aquatic animal. For mythological monster, see Lernaean Hydra. For other uses, see Hydra (disambiguation).
Hydra
Hydra-Foto.jpg
Hydra species
Scientific classificatione
Kingdom: Animalia
Phylum: Cnidaria
Class: Hydrozoa
Order: Anthoathecata
Family: Hydridae
Dana, 1846
Genus: Hydra
Linnaeus, 1758[1]
Species[1]
List[show]
Hydra (/ˈhaɪdrə/ h-EYE-drə) is a genus of small, fresh-water organisms of the phylum Cnidaria and class Hydrozoa. They

Respiration and excretion occur by diffusion throughout the surface of the epidermis, while larger excreta are discharged through the mouth.[7][8]

Nervous system
The nervous system of Hydra is a nerve net, which is structurally simple compared to more derived animal nervous systems. Hydra does not have a recognizable brain or true muscles. Nerve nets connect sensory photoreceptors and touch-sensitive nerve cells located in the body wall and tentacles.

The structure of the nerve net has two levels:

——————————
had to cut off because Ralph.