9 Fluid thioglycolate medium can be used to determine the oxygen tolerance of an organism because a There is no oxygen in the medium preventing the growth of aerobes b There is high concentrations of oxygen at the top of the medium and low concentrations at the bottom of the medium providing an oxygen gradient c There is low concentrations of oxygen at the top of the medium and high concentrations at the bottom of the medium providing an oxygen gradient d The concentration of oxygen is equal throughout the medium preventing the growth of anaerobes 10 A significant rain event has caused the fertilized topsoil of a farm to be washed into a nearby stream This topsoil which is nitrogen rich causes an influx of nitrogen into a nearby stream which was previously nitrogen limited What is the likely effect of this eutrophication event a Organisms that were not good at scavenging for nitrogen will benefit the most from this event and may now outcompete other organisms in the environment resulting in a change in the overall microbial community b Organisms that specialized in nitrogen scavenging will benefit the most from this event and may now outcompete other organisms in the environment resulting in a change in the overall microbial community c All organisms within the stream will increase in number because they can all benefit from the new nitrogen supply so there will be no change in the relative abundance but there will be an increase in overall bacterial numbers d There will be no effect on the microbial community 11 Food companies pasteurize dairy products because a They are not licensed to use autoclaves b It is the cheapest way to sterilize food so pasteurization is a cost saving measure c It is a preferable alternative to gamma irradiation because irradiating the food would carry the risk of radiation poisoning to those that consumed the food d This method reduces the number of pathogens to safe levels while preserving the taste and texture of their product 12 Which of the following statements correctly identifies the difference between a disinfectant and an antiseptic a Disinfectants kill or remove pathogens from the surface of inanimate objects antiseptics kill or remove pathogens from the surface of living tissue b Disinfectants completely sterilize the surface to which it is applied antiseptics do not sterilize the surface to which it is applied c Disinfectants are not effective against spores antiseptics are effective against spores d Disinfectants are effective against viruses antiseptics are not effective against viruses