1. natural selection acts on existing traits because you can not evolve into something you didn't have
2. original structures evolve to accomplish new function in order to survive
Answer is thorax...
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<span>a. spinal cord
Spinal Cord is the part of the nervous system responsible for connecting the brain to the body.
</span>The nervous system is divided into two groups. The Central Nervous System and the Peripheral Nervous System.
The Central Nervous System involves the Brain and the Spinal Cord. Its contains the integrative and control centers.
<span>The Peripheral Nervous System involves the cranial nerves and spinal nerves. It is composed of the communication lines between the Central Nervous System and the rest of the body.</span>
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