Need, oxygen is not nessicary, oxygen in not essential.
Phenotype = Observable/Physical characteristics.
Simple because there would be a larger gene pool, more opportunity for variation than a small population which has less of a gene pool and therefore less opportunity for variation.
Complete question:
You will find the complete question in the attached files (PNG)
Answer and Explanation:
You will find the complete answer and explanation in the attached files (PDF) due to technical problems.
Stocking Cap
Hope this helps you!