Biodiversity (College Board AP Biology)

Sand lances of the genus Ammodytes are small fish that function as keystone organisms in several coastal ecosystems. These sand lances are prey fish that support organisms at higher trophic levels. Scientists performed experiments to examine how sand lance populations are likely to be affected by the rising temperatures and CO₂ levels associated with climate change.

Sand lance embryos typically develop and mature into adult fish at low temperatures (approximately 5^oC) and stable, low CO₂ levels (approximately 400 µatm). Over the course of two years, the scientists measured the survival rate of sand lance embryos allowed to develop and mature in a laboratory at three different temperatures, 5^oC, 7^oC, and 10^oC with the level of CO₂ maintained at 400 µatm, 1,000 µatm, and 2,100 µatm for each temperature.

Describe the effect of increased biodiversity on the resilience of an ecosystem in a changing environment.

Justify the scientists' selecting 5^oC as the lowest temperature and 400 µatm as the lowest CO₂ level in their study of sand lance embryo survival.

State a null hypothesis for the experiment.

The scientists claim that a reduction in the population size of the Ammodytes sand lances will affect the stability of the entire coastal ecosystem. Provide reasoning to support the scientists' claim.