ACT (Enhanced)ScienceMedium
A biologist is studying the growth rate of a specific bacterial strain under varying nutrient concentrations. They conduct experiments at 0.1%, 0.5%, 1.0%, and 2.0% nutrient concentrations, measuring bacterial population density after 24 hours. The initial population density was 10^3 cells/mL for all experiments. The results are: 0.1% -> 1.5 x 10^4 cells/mL; 0.5% -> 8.0 x 10^4 cells/mL; 1.0% -> 1.2 x 10^5 cells/mL; 2.0% -> 1.3 x 10^5 cells/mL. Based on these results, which inference can be made about the bacterial growth?
- AIncreasing nutrient concentration beyond 1.0% provides diminishing returns for growth.
- BA nutrient concentration of 0.1% is lethal to the bacterial strain.
- CThe optimal nutrient concentration for this strain is exactly 1.0%.
- DBacterial growth rate is directly proportional to nutrient concentration.
Show answer & explanationAnswer & explanation
Correct answer: A. Increasing nutrient concentration beyond 1.0% provides diminishing returns for growth.
The population density increases significantly from 0.1% to 1.0% (1.5x10^4 to 1.2x10^5). However, increasing the concentration from 1.0% to 2.0% only results in a small increase (1.2x10^5 to 1.3x10^5). This indicates that the benefit of additional nutrients decreases after 1.0%, suggesting diminishing returns.
Why the other options are wrong
- B. The population increased from 10^3 to 1.5 x 10^4 at 0.1%, so it is clearly not lethal.
- C. While 1.0% shows high growth, the experiment didn't test concentrations between 1.0% and 2.0%, so 'exactly 1.0%' cannot be concluded as optimal.
- D. The increase from 1.0% to 2.0% is not proportional to the earlier increases, so this is incorrect.
Inference from Quantitative Data
Drawing logical conclusions or interpretations based on numerical data and observed patterns or trends.
- Requires careful analysis of changes, rates, and magnitudes.
- Distinguish between correlation and causation.
- Avoid overgeneralization beyond the scope of the data.
Memory trick: Numbers tell a story, if you listen for its glory.