Which portion of the upper gastrointestinal system is initially responsible for the mechanical breakdown of food? Liver Mouth Esophagus Large intestine

Mouth

Explanation:

The mouth is the part of the upper digestive tract where the process of mechanical digestion begins. Teeth breakdown the food into smaller pieces. With help of tongue, the food pieces are mixed with saliva which in turn is released from salivary glands. This process of mechanical digestion of food is called chewing or mastication. It converts the food into a soft, flexible, easily swallowed mass called a bolus. Food particles in bolus get dissolved in water to facilitate the chemical digestion by enzymes.

d concave shape of wave rock

explanation:

the concave shape of wave rock is a very good evidence that supports the evolution of earth due to chemical weathering. if we talk about structure of   wave rock, studies have estimated that it is around 2.7 billion years old. it also serves as the foundation of evidence that it was the place where australian continent began to form.

how the structure of wave rock was created?

studies suggest that structure of wave rock was created when the surrounded area was started to weather due to which deposition of material started on the part of land which now contains wave rock.

the structure of wave rock is considered to be one of the best-known landforms in australia. at the height of around 15 cm, there can be found flared slopes which formulate the margins of hyden rock. it is now assumed by geologists that wave rock was created by subsurface water-induced weathering and not by glaciers, waves or wind.

due to deposition of material over the period of long time, the wave rock became tougher and tougher due to weathering from surrounding terrain. this makes it a physical evidence that supports   the evolution of earth due to chemical weathering.

hope it !