The correct option for maintaining biodiversity in a managed ecosystem is B. Controlled burning. Detailed Explanation Why Controlled Burning is Correct:

1. Definition and Purpose: Controlled burning, also known as prescribed burning, is a land management technique where fire is intentionally set under controlled conditions. The primary purpose is to reduce excess vegetation, manage ecosystems, and promote the growth of certain plant species that are beneficial for biodiversity.
2. Ecosystem Benefits:
3. Nutrient Cycling: Fire can help recycle nutrients back into the soil, making them available for new plant growth. This process can enhance soil fertility and promote a diverse range of plant species.
4. Habitat Creation: Many ecosystems, such as grasslands and certain forests, depend on fire to maintain their health. Controlled burns can create a mosaic of different habitats, which supports various species of plants and animals.
5. Invasive Species Control: Fire can help control invasive species that may outcompete native species for resources. By reducing the biomass of these invaders, controlled burns can give native species a better chance to thrive.
6. Biodiversity Promotion: By creating a variety of habitats and promoting the growth of native species, controlled burning can significantly enhance biodiversity. It allows for the coexistence of different species, which is crucial for a balanced ecosystem.

Why the Other Options are Incorrect or Weaker:

• A. Monoculture Farming:
• Definition: Monoculture farming involves growing a single crop species over a large area.
• Impact on Biodiversity: This practice is detrimental to biodiversity as it reduces the variety of plants and animals in an area. It can lead to soil degradation, increased vulnerability to pests and diseases, and a loss of ecosystem resilience. Monocultures do not support diverse ecosystems and can lead to the extinction of local species.
• C. Invasive Species Introduction:
• Definition: This practice involves introducing non-native species into an ecosystem.
• Impact on Biodiversity: Invasive species often outcompete native species for resources, disrupt food webs, and can lead to the decline or extinction of native species. This practice is widely recognized as one of the leading causes of biodiversity loss globally. Therefore, introducing invasive species is counterproductive to maintaining biodiversity.
• D. Urban Expansion:
• Definition: Urban expansion refers to the growth of cities and towns into previously undeveloped areas.
• Impact on Biodiversity: Urbanization typically leads to habitat destruction, fragmentation, and pollution, which severely impacts local wildlife and plant species. As natural habitats are converted into urban areas, biodiversity is often lost, making this option detrimental to maintaining biodiversity.

Summary of Key Points

• Controlled burning is an effective method for maintaining biodiversity by promoting nutrient cycling, creating diverse habitats, and controlling invasive species.
• Monoculture farming reduces biodiversity by focusing on a single crop, leading to ecosystem degradation.
• Invasive species introduction disrupts local ecosystems and threatens native species, leading to biodiversity loss.
• Urban expansion destroys natural habitats and fragments ecosystems, further harming biodiversity.

By understanding these concepts, students can appreciate the importance of sustainable practices in ecosystem management and the role they play in preserving biodiversity.