The answer is foreign pathogens.
Answer:
Explanation:
Mutations may or may not affect the phenotype because they can occur in coding or non coding areas of the DNA. If they occur in coding areas of the DNA, the protein that is coded in that part could be processed incompletely or have a different amino-acid in some part of its structure, this would affect the phenotype. If they occur in non coding areas, this would have no effect on the phenotype.
A psychological disorder or a mental disorder is compose of behavioral and psychological symptoms impacting on areas of one's life causing further problems. When a psychiatrist like Dylan works on the causes of the disorder such as chemical imbalances, he is now working on the Biological perspective of the treatment.
Hey there!
Number 3, "has more people than ever before" is correct. As there are more people, there is a greater need more resources.
Hope this helped, have a good night!