Organisms in the environment

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  • Organisms in the environment
    • Photosynthesis
      • carried out by green plants and algae
        • chlorophyll in the chloroplasts absorbs the Sun's light energy
      • carbon dioxide + water - (+ light energy) - glucose + oxygen
        • Co2 is taken in by leaves, H2o is taken in by roots, chlorophyll traps the light energy, this energy is used to convert Co2 and H2o into glucose
          • oxygen is released as a by-product of photosynthesis
          • some glucose is converted into insoluble starch for storage
      • by testing leaves with iodine solution we can identify starch and show the occurrence of photosynthesis
        • variegated leaves have green patches (with chlorophyll) and white (w/o chlorophyll
        • only green patches will turn the iodine blue-black to show starch
    • Limiting factors
      • lack of light and Co2 will slow down photosynthesis
      • cold will stop enzymes working effectively- slowing down photosynthesis
      • The independent variable- the one being teseted
      • The dependent variable- the one you measure
    • How plants use glucose:
      • converted into soluble starch for storage
      • used for respiration
      • used to produce cellulose to strengthen cell wall
      • used to produce protein
        • mineral ions (nitrate ions) are needed to produce protein
    • Controlling photosynthesis
      • evaluate benefits of increasing growth with increased cost of heating/lighting and providing Co2
        • growing plants in a Greenhouse/Poly-tunnels makes it easier to control environment conditions
    • Organisms in their environment
      • Physical factors that may affect the distribution of organisms:
        • Temperature, availability of: nutrients, light, water, oxygen, carbon dioxide
      • quantative data can help descirbe how physical factors might by affecting the distribution of organisms
        • quantitative data can be obtained by:
          • random quantitative sampling using a quadrat or sampling along a transect
            • in a large field enough random quadrats must be placed to be sure the sample is representative of the whole field (sample size)
            • an estimate is usually given as a mean per square metre
    • Valid data
      • The method used in an investigation must answer the question which has been asked
      • Measurements must be repeatable and reproducible
      • All the variables should be controlled in an investigation



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