Describe how a group of students could estimate the total number of dandelion plants growing in a local field.
Read the passage below about Himalayan Balsam.
Himalayan Balsam: A threat or an asset?
Himalayan Balsam was introduced to gardens because of its attractive pink flowers. These flowers produce large amounts of sweet nectar, which highly attracts bees and other pollinating insects. Some local populations of bees have significantly increased in areas with Himalayan Balsam. Small mammals like voles and field mice use the dense growth of balsam for shelter.
However, Himalayan Balsam grows very rapidly, reaching up to 2.5 m tall, and spreads its seeds aggressively. In many riverbanks, it completely shades out and kills native ground plants. Consequently, when the balsam dies back in winter, the riverbanks are left bare and suffer from severe soil erosion. Studies show that while total pollinator abundance is high, the variety of different wildflower species and specialist insect species in these areas has significantly dropped.
Some conservationists say Himalayan Balsam is a 'threat' but others see it as an 'asset'.
Use information from the passage to explain these different opinions about Himalayan Balsam.
In your answer use ideas about:
67 exam-style questions on OCR GCSE Biology 4.1 Ecosystems, covering 4.1.1 Cycling of materials in ecosystems, 4.1.2 Microorganisms in cycling materials, 4.1.3 The carbon and water cycles, 4.1.4 Factors affecting decomposition, 4.1.5 Levels of organisation in an ecosystem, 4.1.6 Abiotic and biotic factors affecting communities, 4.1.7 Interdependence and competition, 4.1.8 Trophic levels, 4.1.9 Pyramids of biomass, and 4.1.10 Efficiency of biomass transfers. Each one has a worked solution and a mark scheme showing where the marks go.