Movement of the elbow joint movement is limited to

Being a hinge joint, the only movements allowed by the elbow are flexion and extension of the joint and rotation of the radius. The range of motion of the elbow is limited by the olecranon of the ulna, so that the elbow can only extend to around 180 degrees.

Explanation:

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.

sorry, but you do not have posted the diagram.