Read the passage and answer the questions:

 Water constitutes approximately 60% of the human body and plays a critical role in nearly every biological function, from regulating temperature to facilitating cellular metabolism. Despite its vital importance, adequate water intake is often overlooked in daily health routines. Dehydration, even at mild levels, can impair cognitive performance, reduce physical endurance, and compromise cardiovascular function. Conversely, over hydration—though rarer—can lead to hyponatremia, a potentially life-threatening condition caused by diluted blood sodium levels. 

The amount of water an individual requires varies significantly depending on factors such as age, body size, environmental conditions, and levels of physical activity. While conventional wisdom suggests a daily intake of eight glasses, modern research advocates for a more nuanced approach, emphasizing hydration cues like thirst and the colour of urine as more accurate indicators of bodily needs. Furthermore, water intake is not solely dependent on direct consumption; foods with high water content, such as fruits and vegetables, also contribute substantially to hydration. 

In contemporary society, where caffeinated beverages and processed foods are increasingly prevalent, maintaining optimal hydration demands conscious effort. Unlike water, many popular drinks act as diuretics, increasing fluid loss and potentially exacerbating dehydration risks. Health professionals, therefore, encourage not only regular water consumption but also the cultivation of habits that support overall fluid balance, such as moderating caffeine intake and choosing water-rich foods.

In the sentence

 "The mechanical extraction of minerals may cause irreversible damage to species uniquely adapted to these high-pressure, low-light environments — many of which remain undiscovered," 

The clause "many of which remain undiscovered" is an example of which type of clause?