The decline of the honeybee population, known as colony collapse disorder (CCD), has been a major concern for ecologists and agriculturalists. While many factors have been proposed, recent research points to three primary causes. First, the widespread use of neonicotinoid pesticides, which are systemic and persist in plant tissues, has been shown to impair bee navigation and foraging behavior. Studies have found that even sublethal doses can disorient bees, causing them to fail to return to their hives. Second, the parasitic Varroa mite weakens bees by feeding on their hemolymph and transmitting viruses, such as deformed wing virus. Mite-infested colonies often exhibit reduced brood survival and increased winter mortality. Third, habitat loss due to intensive agriculture and urbanization reduces the diversity and abundance of floral resources, leading to nutritional stress. Bees that lack access to varied pollen and nectar sources have weaker immune systems, making them more susceptible to pathogens and pesticides. Together, these three stressors—pesticides, mites, and habitat loss—are the principal drivers of CCD, according to recent scientific consensus.
🎧 听力讲座
🎯 模拟考试环境：先点「播放讲座」听完内容，再作答。听力原文默认隐藏。
The reading attributes colony collapse disorder to three main causes, but the lecture argues that these factors are not as straightforward as presented. First, regarding neonicotinoids, the speaker notes that while these pesticides can affect bees in laboratory settings, field studies show that real-world exposure levels are often much lower. In fact, many CCD cases have occurred in areas with minimal pesticide use, suggesting that other factors, such as viral infections, may be more critical. Second, the Varroa mite is indeed harmful, but the lecture points out that mite infestations are not new; beekeepers have managed them for decades with treatments. The recent spike in CCD does not correlate with mite levels, and some healthy colonies have mites without collapsing, indicating that mites alone cannot explain the phenomenon. Third, habitat loss is a broad trend, but the speaker emphasizes that CCD often strikes in spring when flowers are abundant, not during winter when food scarcity is typical. Moreover, bees that are provided with supplemental feeding still suffer CCD, undermining the nutritional stress hypothesis. The lecture concludes that the causes of CCD are likely more complex, possibly involving a combination of factors or an unknown pathogen, and that the reading oversimplifies the issue.
📝 Hướng dẫn viết Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific points made in the reading passage.
📊 TOEFL Integrated Writing Rubric
Content Accuracy: Accurately capture the relationship between lecture and reading
Information Completeness: Cover all key counter-arguments from the lecture
Structure & Coherence: Logical organization and progression
Language Use: Grammar, vocabulary, expression accuracy
Scored 0-30 based on holistic scoring (original 0-5, scaled to 30).
