plants + crops

• geotrophic


  growth in direction of gravity
• phototrophic


  growth in direction of light
• three main factors that limit the rate of photosynthesis: 

  • Temperature 
  • Light intensity
  • Carbon dioxide concentration
• fertilisers provide crop plants with nitrogen, phosphorus and potassium
• • Plants are selectively bred by humans for development of many characteristics
  • Disease resistance in food crops
  • Increased crop yield
  • Hardiness to weather conditions (eg. drought tolerance)
  • Better tasting fruits
  • Large or unusual flowers
• • Nitrogen:
  • Needed to make amino acids which are the building blocks of proteins
  • Lack of nitrogen causes weak growth and yellowing of the leaves of plants
  • Phosphorous:
  • Needed to make DNA and cell membranes
  • Lack of phosphorus can cause poor root growth and discoloured leaves
• • Potassium:
  • Allows enzyme reactions to take place to produce ATP in respiration as well as being needed for the enzymes involved in photosynthesis
  • Lack of potassium can cause poor growth of flowers and fruits, as well as brown spots on leaves
  • Magnesium:
  • needed to make chlorophyll
  • lack of mg causes yellowing leaves between veins of leaves
• A population is defined as a group of organisms of the same species living in the same place at the same time
• A community includes all of the populations living in the same area at the same time
• An ecosystem is defined as all the biotic factors and all the abiotic factors that interact within an area at one time