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

National 4/5 Biology

Section 4: Photosynthesis

Limiting factors


What do we know so far

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

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

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

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

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

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

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

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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