Final Exam Questions

Q: Decribe how the development of life on early Earth is an example of succession.

A: In a pristine environment, early succession begins with R-selected species who reproduce quickly and change their surroundings enabling other species to colonize. An example of that changing condition would be early blue-green algae who first produced oxygen, enabling respiring heterotrophs to exist. We can also see how species populations changed with succession.

Q: How can understanding of evolution and community interactions be linked to conservation or policy in general?

A: Understanding where a species fits into the community can inform decision makers on their relative importance. The absence of wolves in Yellowstone Park, for example, led to decreased vegetation (trophic cascade)—thus the presence of the top predator affects the overall health of the ecosystem. Such knowledge could also help decision makers to preserve endangered species (on what do they depend? What population pressures limit their growth) and inform policy

Q: Researchers in Yellowstone Park noticed that vegetation on river banks present in historical chronicles of the park no longer existed. During the same period, wolves were completely absent from the park. How could these two phenomena be linked?

A: This could be an example of a trophic cascade within a system of 3 trophic levels. When the top predator disappears from the system, the primary consumers increase in number thereby reducing the autotrophs at the base of the trophic pyramid.

Q: Why is there more than one type of photosynthesis? Explain using evolution and natural selection.

A: Evolution and natural selection are based upon the most “fit” individuals being those who reproduce and pass on their “fitness” to offspring. Within different climates, different traits in plants will be desirable. In a drier climate, plants which use the least water will be selected for; those that use CAM in deserts (or C4 in grasslands) will survive better and reproduce more than those who use C3. These same C4 and CAM plants will not, however, have a competitive advantage in wetter climates; they will not grow or reproduce as fast as C3 plants.

Q: What would soil quality in a tropical rainforest be like before and after deforestation? Why?

A: Before deforestation, rainforest topsoil would be extremely rich in decomposing organic matter. The heat and humidity present, added to the accumulated organic detritus, would be ideal for that decomposition and the production of humus. The nutrients would not penetrate very deeply in the soils. After deforestation, the soil quality would quickly become poor. There would not be the influx of leaf litter and other detritus from the forest to give new inputs of nutrients to the soil. Decomposition would continue apace. Lack of nutrients in deeper soil would prevent that from being a nutrient source (plowing etc). One might also think about the impacts of carbon capture…

Q: Let’s say a family member says to you over Christmas:
Who cares about climate change? Why does action need to be taken, and why is it urgent? How would you answer them using what you've learned in 509?

A: Effects we’re already seeing: sea level change (melting of polar ice) and threat to coastal populations. Regional changes in climate (temperature, weather effects). Tipping points and earth’s climate history!

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