不总是正确的。一个很好的例子是食物网(深海热液喷口)[1]。在排气系统中,细菌利用硫化氢的化学能量产生糖没有任何阳光(没有光合作用)。然后,一些动物(如浮游动物)在发泄捕食细菌(主要消费者),而其他饲料的主要消费者(二级消费者)。(这里有一个例子活动触及这个食物网。][2][!(热液喷口食物链)[3]][3]来源:https://prezi.com/enzc3iqcvizk/hydrothermal-vent-ecosystem/添加一些关于主要的消费者是任何以生产者为食的生物。分类消费者的想法有点假。生产商是分类清晰,因为你可以清楚地看到光合作用或化学合成的生物,从那里开始。我们可以看看消费者是基于美元\三角洲^{13}加元([en.wikipedia.org/wiki/%CE%9413C][4])和$ \三角洲^ {15}N ([en.wikipedia.org/wiki/%CE%9415N] [5])。当你移动营养级,你的美元的比例\三角洲^{13}和$ \加元三角洲^ {15}N增加美元。 Even for humans, depending on how much meat you eat you get different signals (e.g., [pnas.org/content/117/33/20044][5], Figure 1). In your case, the omnivore will have a signal that includes higher $\delta ^{15}N$ values because of their feeding on other animals and therefore they will be classified as a secondary consumer. In order for omnivores to be classified as a primary consumer, their $\delta ^{15}N$ should be close to the one for producers or better to organisms with a complete "vegetarian" diet. That is not the case for omnivores. In a lot of these cases, there is a gradient of values of $\delta ^{15}N$ depending on the diet of the specific omnivore. In fact, scientists look at the $\delta ^{15}N$ values of different individuals to determine their eating habits and in some cases where in the habitat they are feeding. There is a lot of variability on this depending on organisms and even life stages. Classifying organisms as primary/secondary consumers misses the nuance and oversimplifies the complex food web that we observed in the environment. [1]: https://oceanservice.noaa.gov/facts/vents.html [2]: http://www.forsea.org/wp-content/uploads/2019/08/F9U510TGST.pdf [3]: https://i.stack.imgur.com/JXrEj.jpg [4]: http://en.wikipedia.org/wiki/%CE%9413C [5]: http://en.wikipedia.org/wiki/%CE%9415N