Are there any animals without nervous system?
Sponges are the only multicellular animals without a nervous system. They do not have any nerve cells or sensory cells. However, touch or pressure to the outside of a sponge will cause a local contraction of its body. The hydra has a nervous system characterized by a nerve net.
What organisms have no brain or nerves?
The animal that has a nervous system but no brains belong to the phylum Coelenterata class Hydrozoa. It contains the nerve cells and the unpolarised nerve cells of the epidermis in the organism form the nerve net but there is no brain presence in the brain.
Do earthworms have nervous system?
Earthworms have a simple nervous system. The cerebral ganglion is connected to a ventral nerve cord that runs the length of the body.
Do invertebrates have a nervous system?
2. The neural capacity of invertebrates. Except for the cephalopods, invertebrates have small nervous systems, consisting of many small brains (ganglia). Because of the small number of neurons and the distributed organization of their nervous systems, invertebrates are thought to have limited cognitive capacity6.
What was the first animal to develop a nervous system?
The flatworms were the first invertebrates to exhibit bilateral symmetry and also the first to develop a central nervous system with a brain.
In which animal nerve cell is present but the brain is absent?
Hydra
Hydra which belongs to the phylum coelenterata has nerve cells but no brain. Its nervous system consists of nerve cells and their processes.
What animal has the most primitive nervous system?
Based on the genomic data, it appears that the most primitive organism with all of the true components for synaptic transmission is the pancake-shaped Trichoplax. So does Trichoplax possess the cellular components of a recognizable nervous system? In the light of the new work by Smith et al.
What is the most primitive nervous system?
The diffuse nervous system is the most primitive nervous system. In diffuse systems nerve cells are distributed throughout the organism, usually beneath the outer epidermal layer.
