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Question
Which of the following organisms lack(s) a brain?
Which of the following organisms lack(s) a brain?
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Solution
The correct option is C Hydra
Hydra is the first animal in the course of evolution which shows the beginning of 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.
Insects have a well organized nervous system where a brain along with a number of ganglia and nerves are present.
Octopus has a highly developed brain.
Planaria shows the beginning of cephalization (head formation). It has 2 nerve cords (bundle of nerve fibres) that join together to form the rudimentary brain.
Hydra is the first animal in the course of evolution which shows the beginning of 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.
Insects have a well organized nervous system where a brain along with a number of ganglia and nerves are present.
Octopus has a highly developed brain.
Planaria shows the beginning of cephalization (head formation). It has 2 nerve cords (bundle of nerve fibres) that join together to form the rudimentary brain.
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