Question 18M.3.HL.TZ1.4
| Date | May 2018 | Marks available | [Maximum mark: 6] | Reference code | 18M.3.HL.TZ1.4 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Describe, Explain | Question number | 4 | Adapted from | N/A |
The diagram shows one of the stages in neurulation.
Describe what happens next in neurulation.
[2]
a. neural plate moves/folds/bends inwards to form a groove
b. cells multiply/edges increase in height
c. borders/edges of neural plate join/form neural crest
d. neural tube forms/separates from rest (of ectoderm)
Explain the causes of spina bifida in vertebrates.
[2]
a. spine/spinal cord does not form properly
OR
incomplete closure of embryonic neural tube/ tissues around the neural tube do not fuse
b. lack of folic acid/folate (B9 vitamin) in pregnancy
c. genetic/family history
d. exposure to certain medication/environmental conditions during pregnancy
Explain the process of neural pruning.
[2]
a. development of vertebrate nervous system results in overabundance of neurons/connections
b. unused neurons/synapses are lost
c. neurons destroy themselves by programmed/natural cell death/apoptosis
d. removal of dendrites from neurons