1 Transformation: bacteria simply absorb, across their cell membrane and cell wall, DNA that is floating around in the environment. 2  Conjugation: bacteria directly transfer DNA from one bacterium to another through structures called pilli. Transformation: bacteria simply absorb, across their cell membrane and cell wall, DNA that is floating around in the environment. 2  Conjugation: bacteria directly transfer DNA from one bacterium to another through structures called pilli.
Food begins its journey through the digestive system in the mouth, before being pushed by a series of involuntary muscle contractions through the esophagus, then the stomach, and then the small and large intestines.
The esophagus is the food tube, or gullet, that carries food and liquid from the mouth to the stomach. The stomach churns the food and secretes a strong acid that aids in digestion. A specialized muscle, known as the lower esophageal sphincter (LES), is located at the end of the esophagus.