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Investigation into whether light intensity affects the diversity of animal species in a stream.

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Introduction

Peter Tran Biology A2 Coursework Investigation into whether light intensity affects the diversity of animal species in a stream Introduction Fouldon Common, situated in West Norfolk, is a large Common which had been used as grazing land for many hundred years. As this use faded, much of the Common has developed plant life and many different habitats in which many organisms. This investigation is to be performed on Fouldon Common, the stream to be more precise. The stream runs along the edge of the common and it's spring-fed. It is a pleasant habitat and large variety of stream life can be found including some fish, sticklebacks and stone loaches, etc and a range of insects, especially mayfly larvae, stonefly larvae, flatworms, leeches and Great diving beetles. Organisms survive in many different microhabitats and organism diversity varies accordingly. Stream life can vary greatly between different habitats and there are many factors, which affect this range in abundance and diversity of organisms. Factors such as water depth, temperature, availability of Oxygen, and light intensity all affect the organisms which may be found in a particular habitat. I have chosen to measure the effect of light intensity on the species diversity in streams of Fouldon Common. In the investigation, streams of varying light intensity must be chosen and representative samples of the species within each site taken in order to determine this factor's effect on species diversity. Prediction I believe that the varying light intensity will affect the species diversity of organisms in the different sites of the stream. The greater the light intensity, the greater the species diversity. ...read more.

Middle

Some mud-burrowers such as larvae of dipteral use respiratory pigments like haemoglobin to help in oxygen uptake, and this shows how adaptations to anaerobic conditions is often needed. Lower oxygen levels in stream means fewer species of organisms can survive. I plan to measure the oxygen levels of each site in my investigation in order to compare this with the light intensity and the species diversity. Light Intensity: Varying light intensities affect the abundance and diversity of species in streams. Lower light intensities in the stream means that less plant life is supported therefore reduces the chances of aquatic organisms surviving as herbivores. However, organisms which feed from detritus (detritivores) thrive in such conditions, so organisms which feed on detritivores can also found in such areas. In areas of higher light intensities, plant life is more likely to survive due to the opportunity of greater photosynthesis processes. This means that more herbivores are likely to survive in such areas as well as those organisms which feed off the herbivores. My Investigation will measure the light intensities at each site and these relative values will then be compared to the oxygen levels and species found in each site. Cloud Cover: Cloud cover can vary every few seconds and therefore affects the light intensity on the stream. Chemical Composition: Changes in nitrate levels from organic pollution may affect the ecology of the stream directly. Photosynthesis: Just about all of the above variables will affect the rate of photosynthesis, which is essential for supporting plant life, therefore animal life as well. Biotic Factors Competition: Competition occurs between two or more organisms. ...read more.

Conclusion

Once all species have been identified, counted and recorded, lower the inspection tray into the water in order to carefully return the organisms to their habitats. This is to be performed once at each location and then repeated twice in order to receive three separate tallies from each location. Safety A number of precautions must be taken in order for this investigation to be performed in a safe and practical manner. Carry equipment securely and do not place equipment in open areas where they can easily be stumbled on. When entering the stream, tread carefully and lightly as submerged objects such as tree trunks are common and depth is difficult to judge. Also tread carefully on the edge of stream as the wet areas may cause slipping. Water from stream can be contaminated; minimal contact should be maintained and hands must be washed after having come in contact with the stream water. Data Analysis In order to analyse the data received, having used the procedures outlined above, data must be accumulated and manipulated. In order to analyse the species organism data; the three tallies from each location are to be accumulated in order to give a separate tally for each site, which shows the different species and their abundance at each location. A graph must then be drawn showing the relationship between the light intensity and species diversity and a graph showing the relationship between oxygen levels and light intensity. The Species diversity Index test and the T-test should be applied in order to analyse the data received. The Species Diversity Index (SDI) or Simpson Index is a very useful way to summarise data and obtain one single figure which will indicate the diversity or richness of a particular habitat. ...read more.

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