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    AP Environmental Science Chapter 3 questions, Part 2

    6. Explain how predators affect the adaptations of their prey.

    Predators exert selective pressure on their prey, leading them to have better adaptations to survive and evade capture. In turn, the predators themselves evolve to become better hunters. This back-and-forth evolutionary process between predator and prey is called coevolution and generally leaves both species more refined.

    7. Competition for a limited quantity of resources occurs in all ecosystems. This competition can be interspecific or intraspecific. Explain some of the ways an organism might deal with these different types of competition.

    Interspecific competition for limited amounts of resources can lead to changing niches for the involved species, where each species starts adapting to use a slightly different resource to reduce competition. Otherwise, prolonged competition for the same resources can lead one population to completely be overwhelmed and die out. With intraspecific competition, the individuals with genes that allow them to have better access to resources will be more likely to reproduce, thus leading to evolution within that species. Alternatively, sympatric speciation can occur leading to two distinct species that fill different ecological niches.

    8. Describe the process of succession that occurs after a forest fire destroys an existing biological community. Why may periodic fire be beneficial to a community?

    Secondary succession occurs whenever a forest fire razes an existing biological community while leaving the topsoil intact. Short-lived plants start growing, soon to be replaced by longer-lived species that thrive on the dead organic matter of the former. Generalists are usually the first animals to settle in the new community. Over thousands of years, these will be in turn replaced by specialists that occupy different ecological niches. A periodic fire is beneficial in that it sets back supreme competitors and allows for less competitive species a better chance to thrive. This can lead to more overall diversity.

    9. Which world ecosystems are most productive in terms of biomass? Which are least productive? What units are used in this figure to quantify biomass accumulation?

    The most productive ecosystems are tropical rain forests and estuaries. The least productive ecosystems are desert and open ocean. The units to quantify biomass accumulation are 1,000/kcal/m2/year.

    10. Discuss the dangers posed to existing community members when new species are introduced into ecosystems.

    New species introduced to an ecosystem can disturb the delicate balance that exists between the original inhabitants. These invasive species sometimes end up dominating existing species and wiping them out, reducing overall biodiversity with not just the extinction of that species, but other species dependent on it too.

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