Animal cells do not have a cell wall or chloroplasts but plant cells do. This is just one example there are several ways. <span />
Increasing the light intensity increases the rate of photosynthesis, until some other factor - a limiting factor - becomes in short supply. At very high light intensities, photosynthesis is slowed and then inhibited, but these light intensities do not occur in nature.
hemistry is the "scientific study of matter, its properties, and interactions with other matter and with energy". ... It is an experimental science in which theories are developed and tested against observations. The goals of physics include explaining and predicting how the universe works. Biology is the study of life.