AP Bio question on elements

Question

approximately 25 elements are known to be essential to living organisms. out of these 25 elements, four (carbon, hydrogen, oxygen, and nitrogen) make up 96% of living organisms. The remaining elements such as iron, sodium, magnesium, potassium, chlorine, phosphorus and calcium are called trace elements because they are found in organisms in minute quantities. The percentages of naturally occurring elements making up the human body are similar to the percentages of these elements found in other organisms. How could you account for this similarity among organisms? Justify your answer.

Answer 1

There are probably multiple justifiable answers to this, but the one that came to my mind was:

 

The need for trace elements could possibly be considered a synapomorphy (shared characteristics among organisms that have a common ancestor). Ions are especially important in pumps in the cell membrane, as they are used anywhere from ATP synthesis to muscle contraction to active transport and neural conduction. Simply put, all living things have basic needs in common, and these needs are met in certain ways that require trace elements, so it makes sense that all living things have them. 

 

- Oxygen is vital to cellular respiration, and iron is necessary to bind oxygen to hemoglobin.

- Phosphorus is present in the phosphate groups of DNA and RNA.

- Sodium, calcium, calcium, and chlorine are used to establish concentration gradients and cell potentials

- Magnesium is also important in muscle contraction

 

That might be a stretch, but I think it makes sense...not sure of the context of the question. Good luck!