EMBRYOLOGY
NERVOUS SYSTEM
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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insects
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jellyfish
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sponges
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octopus
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Detailed explanation-1: -The flatworms were the first invertebrates to exhibit bilateral symmetry and also the first to develop a central nervous system with a brain.
Detailed explanation-2: -Nerve nets are found in species in the phyla Cnidaria (e.g. scyphozoa, box jellyfish, and sea anemones), Ctenophora, and Echinodermata. Cnidaria and Ctenophora both exhibit radial symmetry and are collectively known as coelenterates.
Detailed explanation-3: -Jellyfish have no such central place; in fact, they have two nervous systems. A large nerve net controls swimming and a small nerve net controls all other behaviors, including feeding and spasm response (briefly curling into a ball).
Detailed explanation-4: -Simple nerve nets seen in acoels (basal bilaterians) and cnidarians are thought to be the ancestral condition for the Planulozoa (bilaterians plus cnidarians and, perhaps, placozoans).