1- A light-dependent reaction
2-A cellular respiration
If CO2 was in very small amounts then it would be the limiting factor of photosynthesis, this means the process will take place at a much slower rate because it is lacking one of the raw materials it needs for the process to occur. To find the optimum light intensity you really need all other factors to be at optimum levels or in abundance.
Touching a hot pan and yanking your hand away--That is nervous system.
Going through puberty is controlled by the pituitary gland.
jumping up and down is controlled by the muscular system.
Breathing harder during a jog is controlled by the respiratory system.
Getting energy to sit through class by eating cereal and a banana is controlled by digestive system and muscular system.
hope it helps