(a) A poultry farmer feeds a flock of broiler chickens on a commercial ration containing maize, soybean meal and grit. (i) Name the part of the chicken's di...

(a)(i) The part where food is temporarily stored before entering the stomach is the crop. [1] The crop is a thin-walled expandable pouch in the oesophagus that holds swallowed food and softens it with moisture before it moves into the glandular stomach.

(a)(ii) Grit serves as a grinding agent inside the gizzard: it mechanically crushes and breaks down food, compensating for the fact that poultry have no teeth. [1]

(a)(iii) The muscular organ in which grit is used is the gizzard (also called the ventriculus). [1]

(b) Poultry do not need to chew because they lack teeth entirely. [1] Instead, mechanical breakdown of food is accomplished in the gizzard, where thick muscular walls contract rhythmically to grind food against ingested grit particles. [1] This internal grinding replaces the function that teeth and mastication serve in mammals.

(c) Two differences between the chicken and pig digestive systems (paired comparisons): [4]

1. A chicken has a crop for temporary food storage in the oesophagus; a pig does not have a crop and food passes directly to the stomach. [2]
2. A chicken has a gizzard (muscular stomach) that grinds food using grit; a pig has no gizzard and instead relies on teeth for mechanical breakdown and a single stomach for both chemical and some mechanical digestion. [2]

Other valid pairs: the chicken has a proventriculus (glandular stomach) that secretes acid and enzymes before the gizzard, while the pig has a single stomach combining these functions; the chicken has two caeca at the small-large intestine junction, while the pig has one caecum.