Ageing is a normal process of human development that takes place on several levels: biological, psychological and social although it is not certain what causes ageing, most gerontologists would agree that ageing is the result of a combination of both internal and external processes.  The  "wear-and-tear theory"   compares the human body to a machine that over time wears down from use. According to this theory,  bodily systems receive cumulative damage from both external forces, such as toxins, released as a result of metabolism. Cells become damaged and increasingly fail to reproduce or repair themselves.  They die off in larger numbers as we age. the  "combination theory" explains that influences such as stress and diet,  each person is born with a genetically predetermined life expectancy that cannot be exceeded  This interaction of external factors and internal programming  would account for individual variations in the life span. The mystery surrounding why we age is still a topic of numerous ongoing studies. Perhaps, one day we will truly  know why we age.

The pioneers of science education imagined that its introduction into the curriculum would erase conventionality, artificiality, and prejudice. So, too in their time had the humanists thought that the study of the classics would banish pedantry and superstition. The chief claim for the use of science in the learning process is that it teaches young ones some truths about the universe that we are part of, acquaints them with the highlights of scientific discoveries, and rationally. To some extent, these goals have been reached only in the first of these aims. Young people who have been given this sort of science education will know the basics of physics and chemistry. However, they will know not much more than what they would have learned by picking up scientific hobbies or suing everyday scientific appliances.  

 Once a bird is brought to a rehabilitation center, basic procedures are followed. First, the bird is sedated, if necessary, and examined to detect broken bones, cuts or other injuries. Next, oil is flushed from its eyes and intestines. Heavily oiled birds are then wiped with adsorbent cloths to remove patches of oil. Stomach -coating medicines may be administered orally to prevent additional absorption of oil inside the bird's stomach. The bird is then warmed and placed in a quiet area. Finally, Curtains are often hung around the area to limit the bird's contact with people. 

About fifty years ago, plant physiologists set out to grow roots, by themselves in solutions in laboratory flasks. The scientists found that the nutrition of isolated roots was quite simple. They required sugar and usual minerals and vitamins. However, they did not require organic nitrogen compounds. These roots got along fine on mineral inorganic nitrogen. Roots are capable of making their own proteins and other organic compounds. These activities by roots require the energy of course. The process of respiration uses sugar to make the high-energy compound ATP, which drives the biochemical reactions. Respiration also requires oxygen. Highly active roots require a good deal of oxygen.