The effect of the size of the rock pools on the diversity of animals in the rock pool.

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ROCKY SHORES

The effect of the size of the rock pools on the diversity of animals in the rock pool

Kashaf Iqbal 13 G

Introduction

I am going to investigate how the size of the rock pools effects the diversity of animals in the rock pools.

Rock pools provide a glimpse into the underwater world. Once the “sea's blanket” is taken away, the rock pool is isolated as if it were a small aquarium and its living conditions begin to change. These environments are one of the harshest to be found on the coastline. There are various abiotic factors that affect the diversity of animals in a particular size of rock pools.

Oxygen is one of the factors. Animals need oxygen for breathing. Oxygen is absorbed at the surface of the water. Therefore, animals in shallow rock pools would have more chance of getting oxygen than animals in deeper rock pools. This could have effect on the diversity of animals in deeper and shallow rock pools. Also, rock pools with more plants might have higher oxygen content in the day because plants are making oxygen during photosynthesis.

6CO2  +  6H2O    C6H12O6  +  6O2

Temperature is another abiotic factor that affects the diversity of animals in a particular size of a rock pool. During the day, rock pools are heated by the sun and warm up, but during the night they are cooled. When water warms up, it does not pass the warmth downward easily. Therefore, the small rock pools warm up more so than the large ones. The temperature also depends on how much water evaporates by the wind blowing over the pool.

There are some biotic factors that also affect the diversity of animals in a particular size of a rock pool. Competition is one of the factors. The animals in the rock pools would compete for food in the rock pools. For example, Dog whelks feed on mussels and if there are not enough mussels in one rock pool and too many dog whelks, some dog whelks might not be able to survive.

I am going to carry out my experiment on the middle shore. I have chosen the middle shore because this zone displays a greater diversity of species and it is an area that does not suffer such long periods of exposure and variation in physical factors as the upper shore. At the lower shore, the rock pools are exposed and cut off from the sea for only short periods. So, therefore the middle shore would be a suitable place to carry out the experiment.

The independent variable is the size of the rock pools as this is going to be manipulated. The dependant variable is the diversity index of animals in the rock pools because the diversity of the animals in the rock pools are dependant on the size of the rock pools.

After I have gathered the results I will use spearmans rank correlation coefficient to see if there is any correlation between the diversity of animals in rock pools and the size of the rock pools. Spearman rank correlation coefficient is a value, between -1 and 1, which is used to see how 2 sets of ranks correlate. I can then use the Spearman’s rank correlation coefficient value to compare with the critical value so that I can observe whether my results are statistically significant. A statistically significant result is one which is unlikely to have occurred by chance. We can never be 100% certain that chance has not played a part but if we can be 95% sure (5% chance / probability = 0.05 of results being due to chance) we can reject the null hypothesis and accept the experimental hypothesis. The 5% (p = 0.05) is the level of significance generally used by biologists.

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I can also use Spearman’s rank correlation coefficient value to see the correlation between the two sets of ranks. A coefficient value of ‘0’ means that there would be no correlation between the 2 sets of ranks. A coefficient value of ‘1’ means that there would be perfect positive correlation between the 2 sets of ranks. A coefficient value of ‘-1’ means that there would be perfect negative correlation between the 2 sets of ranks. Any value in between can be described as strong negative/positive or weak negative/positive correlation.

I predict that as the size of the rock ...

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