[[1]] are the animals which do not possess a notochord.

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answer is NON-CHORDATES.

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Detailed Solution

Invertebrates or Non-chordates are animals that do not possess a notochord. The notochord is a flexible rod-like structure that is present in the embryonic stage of all chordates, including fish, amphibians, reptiles, birds, and mammals. Invertebrates include a diverse range of animals such as insects, crustaceans, mollusks, worms, and jellyfish, and they lack a notochord.

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