AIIMS 2013 Biology Question Paper for free online practice with solutions

The human digestive system carries about trillions of microorganisms colonising the gut making an amazing ecosystem that live together in harmony. In this context human intestine is said to be rich in flora and fauna. The microorganisms perform a host of useful functions, such as fermenting unused energy substrates, training the immune system, preventing growth of harmful, pathogenic bacteria, regulating the development of the gut, producing vitamins for the host (such as biotin and vitamin K), and producing hormones to direct the host to store fats. Fish culture is sometimes done in combination with a rice crop, so that fish are grown in the water in the paddy field. Thus, a rice field is an example of ecosystem inhabiting both plants and animals.