Invertebrates
in- = not
vertebra = spine
To provide energy to the body.
Endocrine signaling is hormone based signaling that travels through the blood stream. Many of the sensors and integrating sensors of the endocrine system are located in the brain. The brain barrier contributes to endocrine signalling, such that the brain barrier does not factor in with endocrine signalling. The answer is A
<em>A<u> population </u>is a group of the same kind of living things in a ecosystem.</em>
<em>~I hope this helps! ;)</em>