Photosynthesis Ecosystem and Environment

• Photosynthesis


  The process by which plants use energy from the sun to convert carbon dioxide and water into glucose
• Plants are able to make their own food by photosynthesis
• Photosynthesis


  1. Carbon dioxide + water

  2. Light energy from the sun

  3. Chloroplasts containing chlorophyll

  4. Glucose production

  5. Oxygen released
• Chloroplasts


  Subcellular structures in plants that contain enzymes to catalyse the reactions of photosynthesis and chlorophyll to absorb light energy
• Ways plants use glucose

  • For respiration to release energy
  • Making cellulose for plant cell walls
  • Making proteins
  • Storing as oils or fats
  • Storing as starch
• If a plant can't photosynthesise, it can't make starch
• Starch test


  1. Boil leaf to kill it and stop reactions

  2. Soak leaf in ethanol to remove chlorophyll

  3. Add iodine solution

  4. Leaf turns blue-black if starch is present
• If a plant is kept in a sealed jar with sodium hydroxide solution (which absorbs CO2)

  The leaf will not turn blue-black in the starch test, showing CO2 is needed for photosynthesis
• Oxygen is produced as a by-product of photosynthesis
• The word equation for photosynthesis is: carbon dioxide + water -> glucose + oxygen
• Limiting factor


  A factor that stops photosynthesis from happening any faster, such as light intensity, CO2 concentration or temperature

  
• As light intensity increases

  The rate of photosynthesis increases, up to a point where another factor becomes limiting

  
• As CO2 concentration increases

  The rate of photosynthesis increases, up to a point where another factor becomes limiting

  
• As temperature increases


  The rate of photosynthesis increases, up to an optimum temperature, then decreases as enzymes become denatured

  
• The inverse square law states that light intensity is inversely proportional to the square of the distance from the light source
• Measuring oxygen production can be used to determine the rate of photosynthesis

  
• Using gas sensors and data loggers can also be used to measure the rate of photosynthesis by detecting changes in oxygen or carbon dioxide concentration

  
• n must have been a limiting factor at 0.04% CO2. The limiting factor here isn't temperature because it's the same for both lines (25 °C).
• Relationship between increasing light intensity and the rate of photosynthesis

  1. Increasing light intensity

  2. Increasing rate of photosynthesis

  
• Limiting factor at point B


  Not enough
• As temperature increases


  The rate of photosynthesis increases

  
• Organisms within an ecosystem eat each other. What eats what can be beautifully presented in a food chain or food web.
• Ecosystem levels of organisation

  • Population - All the organisms of one species in a habitat
  • Community - All the organisms (different species) living in a habitat
  • Ecosystem - A community of organisms along with all the non-living conditions
• Food chains


  1. Start with a producer

  2. Producers are eaten by first stage (primary) consumers

  3. First stage consumers are eaten by second stage (secondary) consumers

  4. Second stage consumers are eaten by third stage (tertiary) consumers
• Producers


  Organisms that make their own food, usually using energy from the Sun's radiation. Producers are usually green plants, which make glucose via photosynthesis.

  
• Biomass


  The mass of living material. Biomass can be thought of as energy stored in a plant.
• Biomass is transferred through living organisms in an ecosystem


  When organisms eat other organisms
• Light energy from the Sun supports nearly all life on Earth.
• Consumers


  • Herbivores (animals that eat plants)
  • Carnivores (animals that eat other animals)
• Trophic level


  Each stage (e.g. producers, first stage consumers)
• Food webs


  • Many different species within an environment
  • All the species in a food web are interdependent
• Decomposers


  Microorganisms, such as bacteria and fungi, that break down uneaten remains and organisms' waste products
• Pyramids of biomass are almost always pyramid-shaped because biomass is lost at each stage in the food chain.
• Pyramid of numbers


  Each bar shows the number of organisms at that stage of the food chain, not their mass
• Pyramids of numbers can sometimes be other shapes, not just pyramids.
• Energy is transferred through the living organisms of an ecosystem


  When organisms eat other organisms
• Energy lost from the food chain

  • Used by organisms for repairing and maintaining cells, and for growing
  • Used by animals for respiration
  • In waste materials and uneaten parts of organisms
• You hardly ever get food chains with more than about five trophic levels because so much energy is lost at each stage.
• Efficiency of energy transfer

  Amount of energy available to the next level / Amount of energy that was available to the previous level x 100
• The world's population is rising very quickly.