Compare how light is detected by humans and plants and the significance of such detection

The first 200 words of this essay...

Compare how light is detected by humans and plants and the signifocance of such detection

By Christine Cheng S.5B(5)

For human, the circular muscles contract and the radial muscle relax to decrease the size of the pupil which constrict pupil in bright light, so that less light is allowed to enter the eyes. It can allow human's eyes to be over-stimulated in strong light and prevent damage of the retina. On the other hand, the circular muscle relax and radial muscle contract to increase the size of the pupil which dilate pupil, so that more light is allowed to enter the eye. It can allow human to see when limited light is provided in dim light. Besides, photoreceptors in the retina: rod cells and cone cells are significant in detecting light. Rod cells distribute in retina (except at uellow spot and blind spot). They contain a pigment called visual purple which is sensitive to light in low intensity. It shows that rod cells are important for vision in dim light. Cone cells concentrate at the yellow spot and periphery of retina. They are sensitive to light of high intensity. It shows that cone cells are important for vision