What is the most fundamental difference between plants and animals?

Green plants can produce their own food. They use substances in the environment. This process is known as photosynthesis. In contrast, all animals including humans, get their food either directly from plants or indirectly by eating animals which have eaten plants. So animals take in a wider range of foods than plants.
   Plants are generally stationary. They do not have the power of locomotion. Animals, on the other hand, can usually move around. Therefore, plants appear to be less sensitive than animals although they respond in some ways to light, heat, physical contact and other stimuli.
   In external appearance plants are usually green. They grow in a branching fashion at their extremities. Their growth continues throughout their lives. Animals, however, are very diverse in their external appearance. Their growth pattern is not limited to their extremities but is evenly distributed. Growth occurs in a definite period of time.
   The most basic difference between plants and animals is in the unit of structures and functions: i.e. , the cell. Plant cells have a wall which is nonliving in chemical nature whereas animal cells do not have this characteristic.