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A2 Biology Investigation AN INVESTIGATION TO SEE THE EFFECT OF AN ABIOTIC FACTOR ON THE FREQUENCY AND DISTRIBUTION OF A FRESHWATER INVERTEBRATE (i) Planning Introduction Before a complex biological study can be planned and formulated, the terminology in the title above must be clarified. The investigation requires a sound knowledge of ecology, which essentially is the study of organisms, whether they be animals or insects, and their relationship with the environment in which they live. The title of the investigation states that it is the effect of an abiotic factor that is being investigated, as opposed to a biotic factor. There is a very subtle difference between these two factors. Biotic and abiotic factors can both affect how an organism lives and interacts with the immediate environment. 1. Biotic factors are the effects of all the other living organisms that inhabit the studied ecosystem. Organisms can influence each other in many ways of which predation is only one. Many organisms must compete with one another for food, and there are organisms, which feed directly from others as parasites. ...read more.


Having studied similar mountainous streams on previous occasions it is possible to work out what Upper Gordale Beck will be like. Possible organisms which may inhabit the Upper Gordale Beck ecosystem: 1 Trueworm 14 Cranefly lava 2 River limpet 15 Non-biting midge 3 Freshwater shrimp 16 Biting midge 4 Freshwater mite 17 Diving beetle 5 Swimming mayfly nymph 18 Riffle beetle 6 Flat mayfly nymph 19 Black water beetle 7 Burrowing mayfly nymph 20 Dragonfly nymph 8 Stonefly nymph 21 Alderfly nymph 9 Lesser water boatman 22 Damselfly nymph 10 Cased caddis (stones) 23 Whirligig beetle 11 Cased caddis (vegetation) 24 Snail 12 Caseless caddis 25 Leech 13 Blackfly lava 26 Water fly Although 26 aquatic organisms have been identified above, it is highly possible that throughout the data collection other organisms will be encountered. These must not be ignored and can be easily added to the bottom of the list above if need be. A similar list can be drawn up of abiotic data. ...read more.


pH of the water. Surprisingly this could change quite considerably along just a small length of stream. Differing pHs can be caused by the chemicals farmers put on their land getting into the water. Hence anywhere downstream of a farm may have an unsuitable pH for the normal organisms to live. Percentage of oxygen. This will of course only affect those organisms that breathe using oxygen from the water. However some of the listed organisms do breathe in this way, and it would be a fair assumption to say that these organisms should be more frequent where the oxygen content of the water is higher. Amount of phosphate/nitrate/ammonium. Like pH the amounts of these compounds can change considerably along just a short length of stream. Now that these lists have been drawn up, an abiotic factor can be chosen as the one whose effect should be investigated. Also one particular organism must be selected. Choices Abiotic factor = Flow rate Freshwater organism = Swimming mayfly nymph If upon investigation either of these two do not provide suitable results for experimental writeup, it will be very simple to change the investigation to involve a different abiotic factor or organism. ...read more.

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