Question 18M.3.SL.TZ1.5
| Date | May 2018 | Marks available | [Maximum mark: 5] | Reference code | 18M.3.SL.TZ1.5 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Evaluate, Outline | Question number | 5 | Adapted from | N/A |
Cells destined to become neurons differentiate in the neural tube. They grow and mature under the influence of chemical and other signals. The influence of insulin-like growth factor (IGF) was investigated in vitro using olfactory sensory neurons. The turning angle (direction) and extension of growth of these neurons were measured.
Evaluate the claim that IGF influences turning angle and neuron extension.
[2]
a. turning angle of control is zero degrees whereas with IGF it is much larger
b. neuron extension is greater with IGF than control
c. non-overlapping error bars suggest a (significant) effect on turning angle
OR
overlapping error bars suggest a non-significant effect on neuron extension
Outline the development of neurons from when they are first formed in the neural tube.
[3]
a. an axon grows from each immature neuron (in response to chemical stimuli)
b. each developing neuron forms several synapses (with other neurons)
c. synapses that are not used degenerate
d. neural pruning / loss of unused neurons
e. neural connections can change / increase with experience
f. neurons may migrate and complete development at their destination
