in a food web harm it because the toxins harm one specie while harming others also. When that species is harmed other species that consume them will get intoxicated also.The mosquitos died because those toxins were made to kill them, and the cats died because those toxins spread throughout the food web.Explanation:
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.
Apart from reminding oneself that you are prepared for the presentation. You can carry out a physical exercise like the breathing exercise by taking several deep breaths and exhaling to reduce nervousness. Also you should be mindful that the audience is there to hear you and not to judge you. In that way you can ease out tension.