In response to a stimulus, a brain cell called a neuron will send a signal to the brain

a. respiration and absorption
b. myosin and actin
c. electrical signals and chemical neurotransmitters
d. contraction and relaxation

What is a population? a. all the members of the same species living in the same ecosystem at the same time b. the number of a species living in the same ecosystem over a period of time c. the total number of organisms living in an ecosystem at a point in time d. all the members of a food web in the same ecosystem