The introduction of non-native species into new environments is often viewed negatively, but in certain cases, it can provide significant ecological and economic benefits. One such example is the deliberate introduction of the Asian clam (Corbicula fluminea) into North American freshwater systems. Proponents argue that this species offers three major advantages. First, Asian clams are highly efficient filter feeders, capable of clarifying water by removing suspended algae and particulate matter. This improves water clarity, which benefits aquatic plants that require sunlight for photosynthesis, thereby enhancing overall ecosystem health. Second, the clams serve as a abundant and easily accessible food source for native fish and bird species, potentially boosting their populations and supporting local biodiversity. Third, the commercial harvesting of Asian clams for food and bait has created new economic opportunities for local fishing communities, generating income and jobs that might otherwise not exist. Given these benefits, some ecologists suggest that rather than attempting eradication, we should consider managed introduction of such species in carefully selected habitats where they can provide measurable advantages without overwhelming native ecosystems.
🎧 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 presents a favorable view of introducing Asian clams, but this perspective is fundamentally flawed. First, while clams do filter water, their efficiency can lead to excessive nutrient removal, disrupting the natural nutrient cycle. In many lakes, this has caused a dramatic decline in phytoplankton, which forms the base of the aquatic food web. Consequently, zooplankton and other organisms that rely on phytoplankton starve, leading to a collapse in fish populations rather than an increase. Second, the claim that clams provide food for native species ignores the fact that most native predators are not adapted to consume hard-shelled clams. In reality, the clams outcompete native mussels for space and resources, driving many vulnerable species to extinction. For example, in the Tennessee River, native mussel diversity has plummeted by over 50% since the clam's arrival. Third, the economic benefits are overstated. The Asian clam has low market value and is often considered a nuisance by commercial fishers, as it clogs water intake pipes and damages equipment. In fact, the costs of removing clams from industrial and municipal water systems far exceed any profits from their harvest. Thus, the alleged advantages are either misleading or outweighed by severe negative consequences.
📝 Instrucciones de escritura 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).
