The iris in the human eye contracts and expands, controlling the amount of light that reaches the retina. what types of muscle control this? skeletal and voluntary smooth and cardiac skeletal and smooth smooth and involuntary

smooth and involuntary

The iris in the human eye contracts and expands, controlling the amount of light that reaches the retina. It is because of the activity of the smooth muscles, these muscles are present in the retina of the eye. These muscles alters the shape of the lens by contraction and expansion. These actions of  muscles are involuntary, which means these occur without the conscious choice of the organism. Other examples include breathing, digestion and heart beating.

photosynthesis makes the glucose that is used in cellular respiration to make atp. the glucose is then turned back into carbon dioxide, which is used in photosynthesis. while water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.