Describe the process occurring in the diagram.

State what would occur in the embryo immediately after stage IV.

Outline the consequences of incomplete closure of the neural tube in humans.

a. the process is neurulation ✔

b. ectoderm tissue differentiates to form the neural plate ✔

c. the neural plate «changes shape and» folds ✔

d. «the ends join» to form the neural tube ✔

elongation «of the neural tube» ✔

a. this leads to condition spina bifida ✔

b. some of the vertebrae may not form correctly
OR
incomplete closing of the backbone ✔

c. spinal cord may protrude ✔

d. «may» cause paralysis ✔

This question was fairly well answered by most candidates, and it appears that the process of neurulation is covered well by teachers choosing this option. However, as stated before, students struggled to communicate the process clearly, finding it hard to delineate the steps in an organised, sequential manner. There was also some confusion among weaker students regarding the three primary germ layers during embryonic development – all three layers were suggested by these students. They also used subject-specific terminology such as “neural plate,” “neural fold” and “neural tube” incorrectly.

Most students did not state the correct process here, instead writing about longer term events in the nervous system, or excessively generic terms like “differentiation” and “organ development.”

Candidates’ answers to this question tended to be good predictors of how well they scored on the whole option. Students with little to no knowledge and understanding scored 0 marks. An equal number were able to score 1 mark, usually the marking point for identifying the result as spina bifida, while students who scored well on the whole paper successfully communicated another aspect of the condition. This question is also a good example of the need for students to understand what is being asked first. The question asks students to outline the consequences, but a number of students wrote in some detail about the effect of folic acid deficiency during pregnancy as a cause. One reason for this response may be that the cause of spina bifida has been a question in a recent paper.