Chickadees were given an opportunity to store seeds in 72 possible storage sites consisting of holes drilled in small trees that had been placed in an aviary. Typically, the seeds were placed in only 4 or 5 storage sites. The chickadees were then removed from the aviary, the seeds removed from the storage sites, and each hole covered. A day later, the chickadees were returned to the aviary and they spent nearly 5 times as long pulling at the covers on storage sites than at the covers on sites where they had not stored food. This experiment indicates that chickadees

#Question id: 9210

#Unit 9. Diversity of Life Forms

Overharvesting encourages extinction and is most likely to affect ________.

#Question id: 9211

#Unit 9. Diversity of Life Forms

Of the following ecosystem types, which have been impacted the most by humans?

#Question id: 9212

#Unit 9. Diversity of Life Forms

Burning fossil fuels releases oxides of sulfur and nitrogen. These air pollutants can be responsible for ________.

#Question id: 9213

#Unit 9. Diversity of Life Forms

Suppose you attend a town meeting at which some experts tell the audience that they have performed a cost-benefit analysis of a proposed transit system that would probably reduce overall air pollution and fossil fuel consumption. The analysis, however, reveals that ticket prices will not cover the cost of operating the system when fuel, wages, and equipment are taken into account. As a biologist, you know that if ecosystem services had been included in the analysis, the experts might have arrived at a different answer. Why are ecosystem services rarely included in economic analyses?

#Question id: 9214

#Unit 9. Diversity of Life Forms

Researchers have been studying a rare population of 87 voles in an isolated area. Ten voles from a larger population were added to this isolated population. Besides having ten additional animals, what benefits are there to importing individuals?

#Question id: 9215

#Unit 9. Diversity of Life Forms

Use the following figure to answer the question

Five new individuals were added to a small population of bighorn sheep in 1986, and ten more were added between 1990 and 1994. According to the figure, what occurred in this population after these additions?