EEMB/ES 171 Vitousek & Reiners. 1975. BioScienceName: Discussion questions1. How do the authors define “ecosystem”? Give an example of an ecosystem input, including both a potential source and sink for this.In the paper, the authors define an ecosystem as a system that is open where geochemical functions have inputs from different sources, outputs to different sinks, and internal recycling that also varies.” An example of an ecosystem input would be carbon dioxide. A potential source for carbon dioxide is burning fossil fuels. A potential sink for carbon dioxide would be planting more greenery (plants, flowers, trees, etc). 2. Can you give an example of a biological system that is closed? (Hint: this doesn’t have to be a naturally occurring system, and light can keep entering).An example of a closed biological system is the Biosphere 2 project (even though it ended up failing). 3. What does it mean when an ecosystem is in steady state?When an ecosystem is at steady state it means that the amount of inputs and outputs are equal. Matter in = matter out. In a steady state, in terms of mass an ecosystem has an equal balance of inputs and outputs (one does not outweigh the other). 4. Explain Figure 1.Overall figure 1 summarizes the relationship between maturity of an ecosystem and its ability to absorb/hold nutrients. Figure 1 is split up into 2 parts. 1A displays the rate of biomass as successional time increases. The graph shows that at first, when plant growth first begins to start biomass accumulates at a rapid rate,reaches a peak (where production = respiration, and then declines at a gradual rateuntil it reaches zero again. In graph 1B, non-essential, essential, and limiting outputs are being compared with time in a primary successional sequence. As theEEMB/ES 171 Vitousek & Reiners. 1975. BioScienceName: Discussion questionsgraph shows, limiting elements are held the strongest and can decline to zero. Essential elements are significantly retained, however outcomes don’t approach zero. And non-essential elements are not retained . The dotted line shows that there is a great loss in nutrients after disturbance when looking at as secondary successional sequence. Generally speaking, early in succession, biomass will increases greatly but will eventually peak and decline to a steady state5. How does the age of an ecosystem affect nutrient retention or leakage? Overall, nutrient loss depends on the positions on the net increment curve. Middleaged successional ecosystems have lower nutrient loss than ecosystems that are either very young or very