Hi friends!

I can't quite decipher this graph. The top portion shows P. aurelia bacteria and the bottom one shows P. caudatum bacteria. My professor said that the bottom graph is an example of asymmetric competition (one is better than the other. In this case, the P. aurelia is better). The decrease in fitness is clear as the graph progresses in time in unit days.

What I don't understand is why if both bacterium are mixed in each graph, does one show decrease why the other doesn't. I know that they are being compared to different bacteria. The only thing I can think of is the units in volume are different for each graph. For the top graph the intervals are in units of 50, while the bottom graph is in units of 40 (and therefore more detailed?).

Any clarification would be much appreciated. Thank you in advance.