Answer:
I would say chordates. (Not absolutely sure so double check)
Explanation:
Chordates have a dorsal nerve cord, which is super close to a spinal cord. (Which vertebrates have.)
Because there always needs to be something that starts it off. Eg: If there was no grass, there would be no animals.
Answer:the diagram illustrates the results of non disjunction during gamete formation.
Explanation: