Date | November 2019 | Marks available | 2 | Reference code | 19N.3.SL.TZ0.4 |
Level | Standard level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
Command term | Explain | Question number | 4 | Adapted from | N/A |
Question
The development of the neural tube in the frog Xenopus is shown in the diagram.
[Source: reprinted by permission from Nature Reviews Neuroscience, Gammill, L., Bronner-Fraser, M.
Neural crest specification: migrating into genomics. Nat Rev Neurosci 4, 795–805 (2003) doi:10.1038/nrn1219]
State the name of the stage of embryonic development shown in the diagram.
Identify the part labelled X.
State a consequence of incomplete folding of the neural tube in humans.
Explain how the nervous system develops from the cells of the neural tube.
Markscheme
neurulation ✔
neural plate
OR
neural groove
OR
ectoderm ✔
spina bifida ✔
Accept a description of spina bifida
a. neurons differentiate from neural tube / stem cells ✔
b. axons/dendrites grow ✔
c. «axon growth is» directed by chemicals/growth substances ✔
d. neurons migrate ✔
e. synapses form ✔