Date | November 2016 | Marks available | 1 | Reference code | 16N.3.SL.TZ0.5 |
Level | Standard level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
Command term | Outline | Question number | 5 | Adapted from | N/A |
Question
The diagram shows the early development of the nervous system in embryonic chordates.
Outline the process taking place in the diagram.
State what occurs to structure X immediately following its formation.
Outline how spina bifida could occur during embryonic development.
Markscheme
a. infolding of the ectoderm /neural plate
“Ectoderm” is essential for the mark.
b. formation of the neural tube
OR
neurulation
“Neural tube” or “neurulation” is essential for the mark.
elongation / forms a tube
a. neural tube/structure X does not close properly
b. folic acid/folacin/folate/vitamin B9 deficiency
c. may be due to mutation / genetic condition