B7- Biology across the Ecosystem


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  • All life depends on the solar energy absorbed during photosythesis, it is stored in plant chemicals such as starch.
  • Autotrophs create their own food and energy.
  • Hetrotrophs is an organism that must eat other organisms for food and energy.
  • Chlorophyll in plant cells absorbs light for the process of photosynthesis. The word equation is;

Carbon Dioxide + Water ---------> Glucose + Oxygen

  • Glucose is used for different things, making cellulose, proteins, starch and chlorophyll.
  • Nitrates are absorbed from the soil and added to glucose to form proteins.
  • They are absorbed by the roots by 'active transport'.
  • Starch has little effect on the osmotic balance of the cell, so it is used for energy storage.
  • Photosynthesis can be affected by low temperatures, low carbon dioxide or different lights levels.
  • Human activity is incresing atmoshperic carbon dioxide levels.
  • Compenstaion points points occur when respiration makes as much carbon dioxide as phosynthesis uses.
  • Energy is transferred when living things are eaten or broken down by decomposers.
  • Pyramids of biomass show the food available to the herbivores and carnivores in an ecosystem.
  • Only about 10% of the energy in biomass is passed on at each stage in the food chain. The rest is lost to decomposers or waste heat.
  • Soil contains living organisms, decaying material, sand, clay, air, water and dissolved minerals.
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