It is a vestigial Structure.
Explanation:
En.wikipedia.org<span>A measure of acidity or alkalinity of water soluble substances (pH stands for 'potential of Hydrogen'). A pH value is a number from 1 to 14, with 7 as the middle (neutral) point. Values below 7 indicate acidity which increases as the number decreases, 1 being the most acidic</span>
Answer: Density dependent
Explanation: It is a density dependent because there has is a direct correlation between the ratio of predatory animals to prey animals for an ecosystem to function properly. Otherwise the ecosystem begins to die.
Answer:
A photographer will often include a ruler in the shot to establish scale but always takes a duplicate image without the measuring device. In court, the defense could claim the device covered something important. And of course, pictures are of no value unless they're in context.