Question 19M.3.SL.TZ2.d
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.SL.TZ2.d |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Outline | Question number | d | Adapted from | N/A |
Scientists investigated how relative brain mass varied in primate evolution. The graph shows the relative brain mass for species belonging to different primate groups against time of divergence from the common ancestor of modern humans in million years ago (Mya), 0 being the present era.
[Source: S Herculano-Houzel and J H Kaas, (2011), Brain, Behavior and Evolution, 77, pages 33–44.
© 2011 Karger Publishers, Basel, Switzerland]
Primates belong to the phylum chordata. The neural tube of chordates is formed by the infolding of the ectoderm followed by the elongation of the tube. Outline the process of formation of neurons from this neural tube in primates.
[2]
a. neurons formed by a process called neurulation ✔
b. neurons are «initially» produced by differentiation «in the neural tube» ✔
c. immature neurons migrate to a final location ✔
d. an axon grows from each immature neuron in response to chemical stimuli ✔
e. some axons extend beyond the neural tube to reach other parts of the body ✔
f. a developing neuron forms multiple synapses ✔
In Part (d) many candidates were familiar with the process of neuron formation in primates though some may have been confused by the introduction to the question.
