B1- Sustainability and Interdependence

• Food security is the ability of human populations to access food of sufficient quality and quantity.
• Concerns for food security include:

  • Overpopulation,
  • Won’t guarantee enough quantity.
• Main plant crops include:

  • Cereals,
  • Potatoes,
  • Roots,
  • Legumes.
• Livestock produces less food per unit area than plants because, the shorter a food chain, the more energy it holds at the end. Farm land planted with crops produces far more food than the same land planted with grass to feed livestock.
• Photosynthesis: Process by which green plants absorb light energy to make glucose.
• fates of light hitting a leaf:

  • Absorbed,
  • Transmitted,
  • Reflected.
• A pigment is a substance which absorbs visible light. Pigment appears to be the colour of light which they DO NOT absorb.
• Four pigments:

  • Chlorophyll A,
  • Chlorophyll B,
  • Carotene,
  • Xanthophyll.
• Carotene and Xanthophyll and accessory pigments/ carotenoids.
• Pigments can be separated by thin layer chromatography.
• Advantages of plants having carotenoids:

  Total quantity of light absorbed is greater than it would be if only one pigment is involved. Carotenoids extend the range of wave length absorbed and pass the energy to the chlorophyll for photosynthesis.
• Absorption Spectrum: Shows how much light of each wavelength is absorbed.

  Action Spectrum: Charts effectiveness of different wavelengths of light at bringing about photosynthesis.

  Close Correlation: The two graphs show that the pigments absorb the wavelength of light which are most effective at bringing about photosynthesis.
• In Light Dependent stage (1). The hydrogen ions held in coenzyme NADP and ATP are required for Calvin Cycle.

  
• Calvin Cycle: The process by which carbon dioxide is converted into glucose in the presence of light.

  
• Summary of Photosynthesis: