1. Explain the difference between "species richness" and "species index diversity".
Answer
"Species richness" measures the number of species in an ecosystem. "Species index diversity" also does this but also takes into account the number of individuals in each species.
2. Modern farming techniques have been blamed for the reduction of rural biodiversity. Explain how farming has caused a reduction in biodiversity.
Answer
Modern farming techniques have caused a reduction in biodiversity by reducing the variety of food sources available for herbivores and decreasing the range of habitats. Practices such as hedge removal, the use of fertilizers and pesticides, and monoculture farming all contribute to this decline.
3. Over the past 100 years, artificial fertilisers used by farmers have leached into waterways such as lakes and rivers. This has led to eutrophication and decreased species diversity. Explain how leaching of fertilisers into waterways can lead to decreased species diversity.
Answer
Leaching of fertilisers into waterways stimulates the rapid growth of algae, leading to algal blooms. These blooms block sunlight, preventing aquatic plants below the surface from photosynthesising, which causes them to die. Bacteria then decompose the dead algae and plants, using up oxygen in the process. The resulting lack of oxygen in the water leads to the death of fish and other aquatic species, thereby decreasing species diversity.
4. Thousands of years ago, lakes in northern Europe were populated by whitefish. This population separated into groups with different appearance and behaviour. One population reproduced at the bottom of lakes, while the others lived and reproduced closer to the surface. Scientists have found that pollution in lakes is causing the whitefish populations to merge. They are interbreeding and hybridising. Were the whitefish populations separate species ?
Answer
No, because they can interbreed and produce fertile offspring.
5. Scientists carried out a study to compare the effect of two farming methods on biodiversity. They compared conventional farming, where pesticides and artificial fertilisers were used, with organic farming that does not use pesticides and only uses natural fertilisers. The data collected from these fields was collated and can be seen in the table below. Compare the crop yields in the two types of farming.
Answer
Organic farming produces a much lower yield. There is a significant difference as no overlap in means.
6. Suggest how the scientists could measure crop yields.
Answer
Measure the dry mass of crop (g/m2).
7. Explain what is meant by "natural fertilisers" in organic farming.
Answer
Manure, plant waste ploughed into the soil
8. Explain why farmers use fertilisers.
Answer
Harvesting crops removes nutrients from the soil, which must be replaced.
9. Evaluate the statement "the data above shows that organic farming is better than conventional".
Answer
Conventional farming provides better crop yields, which are needed to feed a large population. It supports slightly fewer hoverflies, farmland birds, and some other species. Organic farming, on the other hand, supports a greater variety of plant species. It sustains more individual birds, though fewer bird species overall. Overall, organic farming results in greater biodiversity, as confirmed by the data in the table.
10. Students investigated the frequency of different invertebrates in three different locations. The data that they collected can be seen in the figure below. Calculate the index of diversity of each site and explain which site has the greatest biodiversity.
Answer
Site 1: (216 × 215) ÷ 10.474 = 4.43
Site 2: (36 × 35) ÷ 246 = 5.12
Site 3: (301 × 300) ÷ 30430 = 2.98
Fewer species but more evenness in Site 2
11. Explain how the use of land as farmland can affect diversity.
Answer
The use of land as farmland can reduce diversity by providing a lower variety of food sources and fewer types of habitats.