

The removal of the wolves began to have a ripple effect on the Yellowstone ecosystem. Without a natural predator, the population size of elk began to expand, and as it did, the preferred food sources of the elks – cottonwood and willow trees – began to dwindle. Cottonwoods especially serve an important role in the Yellowstone ecosystem. This species of tree prefers the banks of streams, where its root system helps stabilize the stream banks, thus preventing erosion and the accumulation of sediment. With the loss of the trees, the aquatic habitats suffered, and for decades ecologists documented the decline of aquatic insect, fish, and bird populations. Over time, scientists were becoming concerned that the food web of the Yellowstone ecosystem was moving towards collapse.
In order to understand the role of the wolves in ecosystems such as Yellowstone, scientists had to piece together information on the evolutionary history of the organisms in the community with an understanding of how the ecosystem functions as a biological system. Coupled with this was some fascinating detective work, with experimental results suggesting that it was the demise of the wolves, and not other ecological factors, that were responsible.
The story of the wolves is a positive one for science. By reintroducing wolves back into Yellowstone in the late 1990s, and closely monitoring not only the health of the wolf population, but also the size and composition of the elk herds, conservation ecologists have been able to document that the Yellowstone ecosystem is beginning to return to a healthy status.
So why did we do this?
Well, within this text you will find that these three same themes – the nature of science, evolution, and biological systems - form the threads that connect the content together. We integrated the cover into the story of biology, and then we built assets around the themes to help the instructors engage their classes. Throughout the text, unit level learning outcomes, feature readings, and new digital assets, are all combined to integrate the themes into the course content. The goal is to enforce the idea that, like the complex interactions of the species in the Yellowstone ecosystem, the many parts of the biological sciences are interconnected, and that by understanding these connections, students can grasp the importance of biology to their lives.
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But this is where it gets interesting. In general, Fusarium prefers moist environments (although it can live in hot, arid regions as well). So, it would make sense that chilis that are found in dry environments should produce less capsaicin, and more offspring, than their more arid, Fusarium-threatened relatives.
To test this hypothesis, researchers at the University of Washington first sampled chili plants along a 185 line in Bolivia that naturally varied in water availability. What they found was that even in the dry environments there were chilis with high amounts of capsaicin, but they only accounted for about 20% of the population. However, as the environment became wetter, the percent of high-capsaicin producing plants increased, and at the extreme end of the spectrum, in the moistest environments, all of the plants were capsaicin producers.
To test the relationship between water-efficiency and number of offspring, the researchers designed a controlled experiment in which identical populations of chili plants were grown under similar experiments and then exposed to either a normal, or water-stressed, environment. The results confirmed that plants with higher amounts of capsaicin produced fewer offspring. Although the direct link between capsaicin and water-efficiency has not yet been determined, it is evident that production of the compound comes at a fitness cost to the plant.
So the next time you bite into a really hot chili, consider that fact that what you are really experiencing is an ancient arms race between a pepper and a fungi – and that the chili you are eating sacrificed its fitness for your spiceness.










