Question: The four sentences (labelled 1, 2, 3, 4) below, when properly sequenced would yield a coherent paragraph. Decide on the proper sequencing of the order of the sentences and key in the sequence of the four numbers as your answer:
1. Complex computational elements of the CNS are organized according to a “nested” hierarchic criterion; the organization is not permanent and can change dynamically from moment to moment as they carry out a computational task.
2. Echolocation in bats exemplifies adaptation produced by natural selection; a function not produced by natural selection for its current use is exaptation --feathers might have originally arisen in the context of selection for insulation.
3. From a structural standpoint, consistent with exaptation, the living organism is organized as a complex of “Russian Matryoshka Dolls” -- smaller structures are contained within larger ones in multiple layers.
4. The exaptation concept, and the Russian-doll organization concept of living beings deduced from studies on evolution of the various apparatuses in mammals, can be applied for the most complex human organ: the central nervous system (CNS).
This question has two possible right sequences. Though the right answer is 2431, the sequence 2341 is also a logical sequence. 2 will definitely open the paragraph. Now the point is should we have 3 or 4 next in sequence. 4 introduces the idea of “Russian Doll” and elaborates on that further in 4. This makes 34 a logical pair. The idea of CNS connects 4 with 1. Thus 2341 seems perfectly logical. However, when we take the official answer, which is 2431, the sequence 31 is also logical because 3 mentions “hierarchy of complex structuresmaller structures contained within larger ones” ...1 says that a similar hierarchy might be there in CNS as well. We believe that this question has two possible sequences.
Hence, 2431 is the correct sequence.