Sunday, October 2, 2011

Ecosystem Scenarios

You have been reading about food webs and trophic levels in our study of ecology. 

1)  Think about, then answer the following question:  
What would happen if all the top predators in an ecosystem were gone?

If all of the top predators were gone in an ecosystem, the level directly below the top, would become "untouchable." Since the ecosystem is a sequence of levels, there will always be a top level, a.k.a. a top predator. 
2)  Read  
The Crucial Role of Predators: A New Perspective on Ecology
Significant Quotes:
"the authors contend that the loss of large animals, and apex predators in particular, constitutes humanity’s “most pervasive influence” on the environment. It amounts, they argue, to a “global decapitation” of the systems that support life on Earth."


"Piece by piece, it’s taken 20 years to accumulate the evidence, and the culmination is in that Science paper — that the world is driven by predators as well as nutrients. We have to pay attention to their health and well-being if we want a healthy ecosystem. Simply eliminating them because we want more prey or because we don’t think they’re important is very misguided."


 “It’s ridiculous to talk only about top-down or bottom-up control,” said Tessier. “Both are happening all the time.”3)   Could a balanced ecosystem exist where there were no decomposers?  producers?  consumers?  What might such an ecosystem look like?
No for all three!!! Without decomposers, nutrients would not re-enter the cycle after an organism dies. Also, the amount of dead organisms would build up because the rate of death is faster than the rate of decomposition without decomposers. Without producers, there would be nothing for primary consumers to eat, then affecting the secondary consumers, tertiary consumers, etc. Without consumers, the population of producers would be uncontrollable and the decomposers/scavengers would die due to lack of consumer organisms. All three components of the trophic pyramid are vital for it to remain continuous. Without any level of the cycle, it would be disrupted and a balanced ecosystem would be impossible. 

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