National 4 5 biology
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National 4/5 Biology. Section 4: Photosynthesis Limiting factors. What do we know so far?. Graffiti On your piece of paper write down continuously everything you know about/related to photosynthesis

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National 4/5 Biology

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National 4/5 Biology

Section 4: Photosynthesis

Limiting factors


What do we know so far?

  • Graffiti

  • On your piece of paper write down continuously everything you know about/related to photosynthesis

  • Now look at what everyone has written and try to think about whether any of it will affect how quickly photosynthesis takes place


What are limiting factors?

  • Limiting factors are any factor that could alter the rate of photosynthesis.

  • There are probably many but the main ones studied are temperature, light intensity and CO2 concentration.

  • Why is this?


This is why

  • Light

    -Light will alter the rate of the first stage (photolysis) as it is light dependant.

  • Temperature

    -Temperature will alter the second stage (carbon fixation) as it depends on enzymes for it to work.

  • CO2 concentration

    -CO2will alter the second stage as it is a raw material in that stage.


How is rate of photosynthesis measured?

  • Rate of photosynthesis measured by:

    -production of oxygen over a set period of time

    -uptake of CO2 over a set period of time

    -production of glucose over a set period of time


Limiting factor graphs

  • What is the limiting factor at point A?

  • Carbon dioxide concentration – as CO2 concentration increases so does the rate of photosynthesis

  • What is limiting at point B?

  • Something else (temp or light intensity) Carbon dioxide concentration is no longer having an effect – rate of photosynthesis is remaining constant even though CO2 concentration is still increasing

B

A


Little bit tricky!?

  • What is the limiting factor at point X?

  • Light intensity – as light intensity increases so does the rate of photosynthesis

  • What is the limiting factor at point Y?

  • Temperature – rate of photosynthesis is less at the lower temperature


The last one

  • In the graph carbon dioxide concentration is limiting at points A1, A2 and A3

  • What is limiting at point X?

  • Light intensity

X


Experiment

  • BBC - Learning Zone Class Clips - Producton of oxygen in plants - Biology Video

  • Discuss how variables were controlled and what variables he actually changed

  • What variables could you investigate in class?

  • Your teacher will show you how to set up two investigations using the plant cabomba


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