Cycles in Ecosystems: Mastery Test During the Carboniferous period, which occurred approximately 360 to 300 million years ago, most of Earth was covered in dense rainforests. These rainforests were sustained by a humid and tropical climate that lasted for most of the Carboniferous period. At the end of the period, Earth's climate became much colder Elnd drier, leading to a wide-scale collapse of the rainforests and a significant loss of vegetation. How might the collapse of the Carboniferous rainforests have affected Earth's carbon cycle? A. The loss of vegetation would have decreased the total amount of carbon in Earth's carbon cycle. B. Over millions of years, the decaying vegetation would have been buried and its carbon turned into fossil fuels. C. The total amount of carbon in the carbon cycle would have increased as the vegetation decayed. D. Over time, the decaying vegetation would have absorbed a large amount of carbon dioxide from the atmosphere. D. Hext

To analyze how the collapse of the Carboniferous rainforests might have affected Earth's carbon cycle, let's evaluate each option provided: **A. The loss of vegetation would have decreased the total amount of carbon in Earth's carbon cycle.** - This statement is misleading. While the immediate loss of vegetation would reduce the amount of carbon stored in biomass, it does not necessarily mean that the total amount of carbon in the carbon cycle decreases. Carbon is continuously cycled through various forms (e.g., atmosphere, soil, biomass). **B. Over millions of years, the decaying vegetation would have been buried and its carbon turned into fossil fuels.** - This statement is accurate. The Carboniferous period is known for the formation of extensive coal deposits from the remains of decaying vegetation. Over time, the burial of this organic matter under sediment would lead to the formation of fossil fuels, effectively sequestering carbon for millions of years. **C. The total amount of carbon in the carbon cycle would have increased as the vegetation decayed.** - This statement is partially true. While decaying vegetation releases carbon back into the atmosphere (as CO2), the overall carbon cycle is complex. The decay process does not necessarily lead to an increase in total carbon; rather, it redistributes carbon between different reservoirs. **D. Over time, the decaying vegetation would have absorbed a large amount of carbon dioxide from the atmosphere.** - This statement is incorrect. Decaying vegetation releases carbon dioxide into the atmosphere rather than absorbing it. Therefore, the collapse of the rainforests would likely lead to an increase in atmospheric CO2 levels. Based on this analysis, the most accurate answer is: **B. Over millions of years, the decaying vegetation would have been buried and its carbon turned into fossil fuels.** This option correctly reflects the long-term impact of the collapse of the Carboniferous rainforests on the carbon cycle.