Genetically, even though they don't look alike or have the same function, they come from the same structure of the last common ancestor.
It is important to determine or know whether an organism is aerobic or anaerobic because from there you would be able to know the perfect conditions for the organism to grow and reproduce. If you are culturing the organism you would need if it needs oxygen and how much of oxygen is needed. Anaerobic organisms does not need the presence of oxygen in order to grow. You can determine an organism that is anaerobic by trying to put them in conditions that dos not have oxygen. After a few hours or days, when you observe that more organisms are present, then most likely it is an anaerobic organism.<span />
I think that a toxin that was introduced into a food web can kill some species but not others because some may have resistances to the toxin, while others, it may be lethal. Also that it did not affect everyone because as Bioaccumulation has stated if affected one organism but their might not be much biomagnification as in much increase in the correlation between the food chains in that area. i think the cat were like the top animal so the key stone animal of the food chain and also it had no predators.