To investigate how light intensity affects the rate of photosynthesis of pond weed at different distances away

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Investigation:  Biology 2

Aim:                 To investigate how light intensity affects the rate of                         photosynthesis of pond weed at different distances away.

Variables:         Light Intensity                         - Independent

                Number of Bubbles Produced        - Dependant

                Amount of CO2                        - Control

                Amount of Water                         - Control

                Temperature                                - Control

                Amount of Sunlight                - Control

                Size of Plant                                - Control

                Time Measured For                - Control

Prediction:        As the light intensity increases (the light comes nearer) the                 rate of photosynthesis will increase as well.  Likewise, as the                 light intensity decreases (the light moves further away) the                 rate of photosynthesis will decrease.

                This is because plants need light to perform photosynthesis.                  However, even if the light intensity is at its highest possible                 the plant may only be able to perform photosynthesis at the                 same rate as if it was a little less.  This is because there won’t                 be enough CO2 or water for the plant perform photosynthesis.                  These are known as limiting factors, and in this investigation                 my limiting factor will be the amount of Carbon Dioxide                         because the plant is aquatic and will therefore be in water.                  The formula for photosynthesis is:

                                                Sunlight

                Water + Carbon Dioxide ----------------        Oxygen + Sunlight

                                                Chlorophyll

                Limiting Factor =

Scientific:        - The amount of CO2 will affect the rate of photosynthesis

Basis                because it will be the limiting factor during my investigation.                  This means that if I have to much of it then there may be                         enough for the light intensity to use this extra CO2 for                         photosynthesis and it will no longer be a limiting factor.  

                - The amount of water will affect the rate of photosynthesis                 because the amount of water will need to be kept quite high                 so that the lamp doesn’t heat the water and make our                         investigation unfair.  If there is a larger volume of water it                 will heat up slower.

                - The amount of sunlight will affect the rate of photosynthesis                 because if it is not kept roughly the same there will be more                 sunlight and therefore the light intensity will be higher.

                - The length of the piece of plant will affect the rate of                         photosynthesis because the longer the piece of plant the more                 leaves it will have and therefore the more photosynthesis it                 will perform and the more bubbles it will produce.

                - The time I measure the number of bubbles for will affect                 the rate of photosynthesis because the longer I time it for the                 more bubbles the plant will produce.

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                - The temperature will affect the rate of photosynthesis                         because the warmer the water is the quicker the plant will                         perform photosynthesis.  There I will use a thermometer to                 measure the temperature and the large volume of water to                         keep it cool.  The temperature will help speed up the rate of                 photosynthesis.

Method:        Step 1- I will collect my equipment and pour 1 litre of water                 into a beaker.

                Step 2- Cut a piece of pond weed 5cm long and place it into a                 funnel.  Attach the funnel to the bottom of the beaker using                 plastercine.  Place a test tube ...

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