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A coral reef is an underwater ecosystem formed as a ridge of mainly calcium carbonate deposits - AQA - A-Level Biology - Question 9 - 2021 - Paper 1
Question 9
A coral reef is an underwater ecosystem formed as a ridge of mainly calcium carbonate deposits. Algae are photosynthesising organisms. Some algae grow on coral reefs... show full transcript
Worked Solution & Example Answer:A coral reef is an underwater ecosystem formed as a ridge of mainly calcium carbonate deposits - AQA - A-Level Biology - Question 9 - 2021 - Paper 1
Step 1
Describe a method that could be used to determine the mean percentage cover of algae on a coral reef.
Answer
To determine the mean percentage cover of algae on a coral reef, one effective method is to use a quadrat sampling technique. First, randomly select multiple locations across the coral reef using random numbers or a random number table. Place a quadrat frame at each selected location. Then, record the percentage of algae cover within the quadrat by visually estimating the area covered by algae. Finally, calculate the mean percentage cover by averaging the data from all quadrats sampled.
Step 2
Explain how succession results in a wide variety of fish living on coral reefs.
Answer
Succession on coral reefs leads to an increase in biodiversity, which is essential for maintaining a vast variety of fish species. As algae grow and provide food sources, various fish are attracted to these areas. Over time, the complexity of habitats increases with more structural components like corals, which offer different niches and shelter. This diversification in resources supports a larger number of species, changes in the structure of communities, and enhances ecosystem resilience.
Step 3
Evaluate the effect of the two fish species on algal growth on coral reefs.
Answer
The evaluation of the effect of fish species on algal growth on coral reefs indicates significant findings. The statistical analysis shows a significant reduction in algal growth for the cages with the ocean surgeonfish (set C), suggesting that this species effectively controls algae. Conversely, there was no significant difference noted between the other sets (B and D) compared to set A, indicating that these fish species do not significantly influence algal growth. Notably, the study suggests that the presence of surgeonfish can reduce algal coverage more than 95%, demonstrating a clear ecological role in maintaining a healthy reef balance. Therefore, including a variety of fish species, especially those that graze on algae, is vital for coral reef health.