Higher Biology

• what causes a demand for increased food production


  - large human population and

  concern for food security
• What is food security?


  the ability of human populations to access food of sufficient quality and quantity.
• Main crop species


  - Cereals

  - root crops

  - legumes
• what must food production be


  - sustainable

  - not degrade the natural resources on which agriculture depends
• ways to improve crop yield


  1) Reduce limiting factors

  2)Protect crops

  3) Replace existing strains of crops with a higher-yielding cultivar (cultured variety).

  4) Develop pest-resistant crop plants.
• ways to reduce limiting factors to improve crop yield


  by adding minerals (fertiliser) or

  water (irrigation systems) to remove factors which maybe limiting plant growt
• ways to protect crops to improve crop yield


  Protect crops from:

  - pests (e.g. insects) by using pesticides

  - diseases (e.g. fungi) by using fungicide

  - competition (from weeds) by using herbicides.
• ways to replace crops to increase crop yield


  Replace existing strains of crops with a higher-yielding cultivar (cultured variety).
• ways to stop pests and improve crop yield


  Develop pest-resistant crop plants
• what produces less food per unit area: livestock or crop plants?

  Livestock produce less food per unit area than crop plants due to loss of energy between trophic levels
• arable land planted with ——- produces more food —- ——- ——— than the same land planted with ———— to ——————-


  arable land planted with crops produces more food per unit area than the same land planted with grass to feed livestock
• why is this not always the case?


  because not all land can be planted with crops, in that case it is more efficient to use land for livestock
• what does all food production ultimately depend on

  photosynthesis
• why do green plants trap sunlight energy?and using what process?


  to produce carbohydrates (food) by a process called photosynthesis
• the fate of light when it hits a leaf


  - most white light is ABSORBED by the pigments in the leaf

  - some light is TRANSMITTED through the leaf

  - some light is REFLECTED off the surface
• why do leaves have several coloured pigments


  because different pigments different wavelengths (colours) of light.
• What is the most important coloured pigment

  Chlorophyll
• action spectrum


  Used to show the rate of photosynthesis at different wavelengths of light
• absoption spectrum


  graph produced to represent the ability of each pigment to absorb different wavelengths of light
• Carotenoids


  Accessory pigments that extend the range of wavelengths absorbed in photosynthesis.
• Why are carotenoids knows as accessory pigments

  as they pass the energy they capture onto chlorophyll
• Name of stage one of photosynthesis?

  light reactions
• Where does the light reactions take place?

  grana of chloroplast
• What happens first during stage one of photosynthesis


  light energy is absorbed by photosynthetic pigments (chlorophyll and accessory pigments)
• What is the light energy absorbed used for


  - Generation of ATP

  - Photolysis (splitting) of water
• What happens to the electron in pigments when light energy is absorbed

  The electrons in the pigment become excited and are raised to a higher energy state
• Where are these electrons them transferred?

  along an electron transport chain releasing energy
• What is energy released used for


  - to generate ATP from ADP and Pi by ATP synthase

  - for photolysis
• Photolysis of water in photosynthesis


  water is split into:

  - oxygen= evolves (released) as a by product

  - hydrogen = is transferred to the coenzyme (hydrogen acceptor) NADP to make NADPH.
• What resources are carried over from first stage to second


  NADPH and ATP
• What is second stage of photosynthesis called? And what is it's aim?

  carbon fixation and is where glucose is made and is a series of enzyme controlled reactions
• What happens first during carbon fixation cycle


  # Carbon dioxide enters the cycle and becomes attached to RuBP

  # This reaction is controlled by the enzyme RuBisCO

  # the Carbon dioxide and RuBP combine to make 3PG
• What happens to the 3PG created


  # it joins with the hydrogen from NADPH and is phosphorylated by the addition of phosphate (Pi ) from ATP which supplies the energy

  # this process produces G3P
• What happens to G3P created


  Some G3P is then used to regenerate RuBP (to continue the process). The remainder is used to synthesise glucose.
• Uses of glucose formed during photosynthesis


  - respiration (respiratory substrate)

  - starch (Storage carbohydrate)

  - cellulose (Structural carbohydrate e.g. cell wall)

  - Biosynthesis pathways (Fats and oils, Nucleic acids, proteins)
• What is plant and animal breeding used to improve


  - characteristics

  - sustainable food production
• Ways breeders develop crops to make them better


  # higher food yields

  # higher nutritional values

  # pest and disease resistance

  # ability to thrive in particular environmental conditions.
• What are plant field trials


  type of investigation carried out in a range of environments
• 3 main purposes of field trials


  1. Compare the performance of different plant cultivars (e.g. species A v species B) under the same set of experimental conditions

  2. Find out the effect of different environmental conditions (treatments) on a new cultivar of crop plant.

  3. Evaluate GM crops (conventional v GM crop)
• What factors must be considered why designing a plant field trial


  1. Selection of treatments to be used 2. Number of replicates to be included 3. Randomisationoftreatments