The most abundant element is oxygen...found in the crust and in the atmosphere.
That waste product would be carbon dioxide.
Because the cells can only use energy in form of ATP.
Its like you can't run a diesel truck on petrol.
A stimulus, the cockroach is sensed by your eyes.
Your eyes transmit nerve impulses from the optic nerve, the a group of sensory neurons, to the brain, the central nervous system.
In the brain, the impulse is then transferred by relay / association neurons to the motor neurons which signals the effector which is the muscle in your legs to contract, making you jump in shock
