Observation

This was a popular question among candidates. Many candidates answered question 2(a) as expected but those that could not name the organs that constitute the alimentary canal of humans in a sequential order lost all the marks. Some candidates started naming from the ‘anus’ and some made spelling mistakes.

Candidates’ performance in 2(b)(i) and (ii) was average. Question 2(c) was poorly attempted and some candidates did not give structures with their functions to score full marks. Some candidates did not qualify the structure they named. E.g. some candidates wrote ‘molar for grinding’ instead of including that molars have broad ridged surfaces.

In 2(d), candidates could not state the roles of pancreas in digestion. Only a few were able to state the pancreatic juice and the enzymes.

 

 The expected answers are:

 

• (a) Organs of alimentary canal of humans in sequence
• - Mouth/buccal cavity;
• - Oesophagus/gullet;
• - Stomach;
• - Duodenum;
• - Ileum/jejunum/small intestine;
• - Caecum/Colon/large intestine;
• - Rectum.                                                                      

NB: Organs in sequence must start from mouth to score.           

Spellings must be correct to score

 

(b) (i) Structural differences between the alimentary canal of a bird and human

Bird	Human
- Beak present/mouth modified to beak	beak absent/mouth present;
- Teeth absent	teeth present
- Crop present	crop absent;
- Gizzard present	gizzard absent;
- Anal pore modified to cloaca	anal pore modified into anus;
- Shorter alimentary canal	longer alimentary canal;
- Appendix absent	appendix present.

 

(ii)  Similarities in the alimentary canal of a bird and human

      They both have mouth; oesophagus/gullet; stomach; duodenum; small intestine;

      large intestine; caecum; rectum.                                            

(c)     Adaptation of the dentition of herbivores for feeding

• - Elongated/curved incisors; for cutting grass/herbs;
• - Thick horny pad; against which the lower incisors bite;
• - Canines are absent/presence of diastema; allows tongue to roll the cropped grass;
• - Broad surfaces of the cheek teeth/molars; for grinding/chewing/masticating;
• - Ridges/furrows on cheek teeth/molars; for grinding/ chewing/masticating.          

 

NB: Function must correspond with structure to score 2 marks

Structure alone x 1 mark. Function alone no mark.

 

(d) Roles of pancreas in digestion

• - Produces pancreatic juices which contain enzymes;
• - Sodium bicarbonate in the pancreatic juice neutralizes the HCl from the stomach/ produces alkaline medium;
• - Pancreatic amylase digests starch to maltose;
• - Trypsin in the pancreatic juice digests protein to peptides/peptones;
• - Lipase in the pancreatic juice digests fat droplets to glycerol and fatty acid.