The developing embryonic brain is shaped by __________.

• A. differences in the rates of blood vessel growth
• B. pressures exerted by the growing skull
• C. variations in the levels of nutrients received across the placenta
• D. an oxygen gradient that promotes growth where oxygen is most concentrated
• E. the selective elimination in neurons and synapses

Answer: (E)

Verified step by step guidance

1. Begin by understanding the concept of neural development in embryos. The embryonic brain undergoes significant changes and growth during development, influenced by various factors.
2. Consider the role of selective elimination in neurons and synapses. This process, known as synaptic pruning, is crucial for the development of a functional and efficient brain. It involves the removal of excess neurons and synapses to refine neural circuits.
3. Evaluate the other options provided: differences in blood vessel growth, pressures from the skull, nutrient variations, and oxygen gradients. While these factors can influence brain development, they do not directly shape the brain in the same way as selective elimination does.
4. Understand that selective elimination is a targeted process that helps in optimizing neural connections, ensuring that the brain develops properly by retaining necessary synapses and eliminating redundant ones.
5. Conclude that the developing embryonic brain is primarily shaped by the selective elimination of neurons and synapses, which is a critical aspect of neural development, ensuring the formation of efficient and functional neural networks.