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Scientists investigated the process of succession on sand dunes - AQA - A-Level Biology - Question 4 - 2018 - Paper 1
Question 4
Scientists investigated the process of succession on sand dunes. They measured the percentage cover of different species of plants on sand dunes of different ages. S... show full transcript
Worked Solution & Example Answer:Scientists investigated the process of succession on sand dunes - AQA - A-Level Biology - Question 4 - 2018 - Paper 1
Step 1
Describe how you would determine the mean percentage cover for beach grass on a sand dune.
Answer
To determine the mean percentage cover for beach grass on a sand dune, I would follow these steps:
- Randomly Select Areas: Use a random method to choose several quadrats on the sand dune. This could involve the use of random numbers or a random number generator.
- Sample Multiple Quadrats: Take a sufficiently large sample size of the quadrats to ensure accuracy and representativeness.
- Calculate Coverage: For each quadrat, visually assess and record the percentage cover of beach grass.
- Compute Mean: Finally, sum up the percentage cover from all select quadrats and divide this total by the number of quadrats to find the mean percentage cover.
Step 2
The scientists concluded that the results shown in Figure 5 were due to succession taking place.
Answer
The scientists likely reached the conclusion that succession is occurring because the graph in Figure 5 shows a clear progression in the mean percentage cover of different plant species over time. As the age of the sand dune increases, the percentage cover of beach grass declines while that of conifers and hardwood trees increases. This suggests a shift in plant communities over time, indicative of ecological succession where the pioneer species (beach grass) are gradually replaced by more established species as conditions improve.
Step 3
Use Figure 5 to explain why the scientists reached this conclusion.
Answer
The data presented in Figure 5 illustrates a chronological change in plant community composition as the age of the sand dune increases. Initially, beach grass dominates the younger dunes, suggesting it is a pioneer species adapted to the harsh conditions. As succession progresses, we can observe a gradual increase in the coverage of conifers and hardwood trees, which represent later successional stages. This shift highlights the transition from pioneer to climax communities, showing that ecological succession is actively taking place.
Step 4
Use Figure 5 to explain the results in Figure 6.
Answer
Although Figure 6 is not explicitly provided, it can be inferred that it likely correlates closely with the trends seen in Figure 5. The observed results could represent additional data points or further breakdown of plant species abundances, showing an increase in biomass or change in species composition that supports the conclusions about ecological succession. If trees are of greater percentage in older dunes, this supports the idea that succession favors larger, more stable species over time.
Step 5
Using evidence from Figure 6, what can you conclude about the net primary productivity (NPP) in the sand dunes that are older than 1000 years? Explain your answer.
Answer
Based on the data we assume may be presented in Figure 6, we can conclude that the net primary productivity (NPP) in sand dunes older than 1000 years remains relatively constant when compared to younger dunes. This suggests that while older dunes have potentially greater biotic diversity, the rate of photosynthesis and respiration achieves a balance, maintaining stability in NPP. If a mature plant community exists, it may indicate efficient usage of resources, allowing NPP to stay consistent despite age.