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Question
Which of the following organisms shows the beginning of the nervous system?
Which of the following organisms shows the beginning of the nervous system?
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Solution
The correct option is B Hydra
Hydra is the first animal in the course of evolution which shows the beginning of the nervous system. It has very simple neurons but no brains. The nervous system is not very well developed. It possesses a primitive neural system in which all neurons are similar and joined to form a nerve net.
Neurons are absent in sponges but they respond to external environments.
Planaria shows the beginning of cephalization (head formation).
Asterias belongs to phylum Echinodermata. Echinoderms have no brain. A circumoral ring of nerves with radial nerves is present.
Hydra is the first animal in the course of evolution which shows the beginning of the nervous system. It has very simple neurons but no brains. The nervous system is not very well developed. It possesses a primitive neural system in which all neurons are similar and joined to form a nerve net.
Neurons are absent in sponges but they respond to external environments.
Planaria shows the beginning of cephalization (head formation).
Asterias belongs to phylum Echinodermata. Echinoderms have no brain. A circumoral ring of nerves with radial nerves is present.
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