2Key areas:Food supply, plant growth and productivityPlant and animal breeding by manipulation of heredityCrop protectionAnimal welfare and behavioural indicators of poor welfareSymbiosisSocial behaviourMass extinction, regaining biodiversity and measuring biodiversityThreats to biodiversity
3Key area 1: Food supply, plant growth and productivity
4Food supplyLI:Describe the problems arising from an increasing human population in terms of food supply.Describe how agriculture can be used to control plant growth.
5Food supply The human population in currently growing. The present human population is:
6United Nations estimate of how the human population could increase.
7Feeding over 7 billion people requires a sufficient and sustainable supply of food. This makes food security a massively important subject for the future of the human race.
8Food security Food security is defined as: Sufficient food must be available at all timesFood securityQuantityQualityAccessFood is sufficiently nutritious and varied to provide a balanced dietPeople have economic means to obtain the available food
9Food security: The challenge Watch these videos Feeding the future and Food securityGet a copy of this article from Science (a highly respected science publication) on Food Security.Divide into small groups. Divide the article up and each read a separate section.After reading discuss each section. Come up with a list of the main challenges in assuring food security in the future.How can biological science contribute to solving these challenges?Produce a A4 summary of the challenges and solutions to be photocopied for each group member.
10Agricultural production The earth possesses 75,000 edible plant species, yet we depend on a few to produce 95% of what we eat.
12Improving yieldsAs the area of land suitable for growing crops is limited, agriculture can:1. Add minerals (fertiliser) or water (irrigation systems) to remove factors which may be limiting plant growth.
132. Replace existing strains of crops with a higher-yielding cultivar (cultured variety). 3. Protect crops from pests (e.g. insects), diseases (e.g. fungi), and competition (from weeds) by using pesticides, fungicides and herbicides.4. Develop pest-resistant crop plants.
14Productivity of arable land Think back to National 5: What were the three ways that energy is lost from a food chain?Energy is lost from food chains in the following ways:Only 10% is incorporated into body tissuesUndigested food and wasteMaintaining body temperatureMovement
15As you move a long a food chain, energy is lost between each trophic level and the next. Cereal plant Farm animal HumanAs a result of this loss of energy livestock production generates far less food per area of land than plant production.90% energy lost90% energy lost10% energy passed on10% energy passed on
16Shorter food chains have much less loss of energy: Cereal plant Farm animal HumanCereal plant Human90% energy lost90% energy lost10% energy passed on10% energy passed on10,000 kJ100 kJ1,000 kJ90% energy lost10,000 kJ10% energy passed on1,000 kJ
17Therefore arable land planted with crops produces far more food than the same land planted with grass to feed livestock.However, not all land can beplanted with crops. In thiscase it is more efficient touse them for livestock.
18Plant growth and productivity LI:Describe the processes underlying photosynthesis.Explain the links between photosynthesis and plant productivity.
19Plant growth: Photosynthesis Reminder of photosynthesis from National 5: Take a piece of blank paper – discuss the following:Write the summary word equation for photosynthesisName the two stages.Describe what happens in each stage.Pass the sheet to the next group. Tick the correct bits and add any corrections.
20What is light?Light is a form of electromagnetic radiation which travels in waves.The distance between two crests on a wave is called the wavelength and is measured in nanometres (nm). (1 nm = 10-9 m)WavelengthLight wave
21Visible light is made up of a spectrum of different colours. Each colour of light hasa different wavelength.Colour in a copy of the visible light spectrum in your jotters.400 nm nm nm nm
22The fate of light when it hits a leaf White light hitting a leaf (or any surface) will be either:ReflectedWhite lightAbsorbedTransmitted
23Light absorption by leaf pigments Leaves contain several coloured pigments of which chlorophyll is the most important.These pigments absorb light energy. These pigments absorb different wavelengths of light.
24Which wavelengths of light are used by plants Your teacher will explain how to extract leaf pigments from nettles.Place the leaf pigments solution in front of a spectroscope. This will show which colours are absorbed by the leaf pigments.
25Collect a leaf and cut into small pieces. Add some propanone and sand into a mortar and pestle.Grind this up, until the propanone turns green.Filter the mixture into a test tube.Hold the spectroscope up towards the test tube and look towards the light.
26violetbluegreenyelloworangeredColour in the normal spectrum. Then colour in a second copy of the spectrum viewed through the leaf pigments:
27Spectrum viewed through Chlorophyll violetbluegreenyelloworangeredThe blue and violet are no longer visible and only some of the red is still seen. These have been absorbed by the leaf pigments.These are most important wavelengths for a plant in photosynthesis.
28Separation of leaf pigments by thin-layer chromatography Follow the instructions for the separation of leaf pigments by chromatography practical.
29Absorption and Action Spectra A leaf contains several pigments which can be separated by chromatography.The main pigments are:Chlorophyll a (blue-green*)Chlorophyll b (yellow-green*)Carotene (yellow*)Xanthophyll (yellow*)* This is the colour of the spot on the chromatography paper
30An absorption spectrum shows the absorption of light of each wavelength by each pigment. An action spectrum shows the rate of photosynthesis at each light wavelength.Comparison of absorption and action spectra reveals a close match – this is good evidence for the importance of leaf pigments in photosynthesis.
32Accessory pigmentsThe xanthophyll and carotene allow the plant to carry out photosynthesis is a wider range of light wavelengths.They are known as accessory pigments as they pass the energy they capture onto chlorophyll a and b.
34The photosynthetic pigments are contained with in the grana The photosynthetic pigments are contained with in the grana. Therefore this is where absorption of light energy and photosynthesis take place.Carbon fixation occurs with in the stroma of the chloroplast.
35Capture of energy and photolysis In the chloroplast, when light energy is absorbed by Chlorophyll a, its electrons become excited and are raised to a higher energy state.High energy electrons are captured by the primary energy acceptor.
36The electrons are then transferred along an electron transport chain releasing energy. This energy is used by the enzyme ATP synthase to generate ATP.Some of the energy is also used to split water into hydrogen – which is picked by by the hydrogen acceptor NADP to make NADPH – and oxygen.
37Primary electron acceptor 1. Light energy is absorbed by the chlorophyll creating high-energy electronsH+H+H+3. Energy also used to split waterOxygenWaterChlorophyll2. Electron passed along transport chain, pumping H+ into grana.H+H+HydrogenH+NADPH+H+H+NADPH4. Hydrogen picked by NADP to make NADPH for carbon fixation (calvin cycle).5. Hydrogen ions used by ATP synthase to make ATP for carbon fixation (calvin cycle).H+H+ATP synthase enzymeADP + Pi ATP
38Calvin Cycle (Carbon fixation) At the end of the first stage of photosynthesis (the light dependent stage), the hydrogen (in the form of NADPH) and the ATP are essential for the second stage – known as the Calvin cycle.This takes place in the stroma of the chloroplast.
40Carbon dioxide enters the cycle and becomes attached to RuBP (ribulose bisphosphate). This reaction is controlled by the enzyme RuBisCO (ribulose bisphosphate carboxylase/oxygenase).The Carbon dioxide and RuBP combine to make 3-phosphoglycerate.
413. The 3-phosphoglycerate then joins with the hydrogen from NADPH and is phosphorylated by the addition of inorganic phosphate (Pi) from ATP which supplies the energy. 4. This process produces glyceraldehyde-3-phosphate (G3P). 5. Some G3P is then used to regenerate RuBP (to continue the process). The remainder is used to synthesis sugars.
42Uses of sugarThe sugar formed during photosynthesis goes onto the following uses:GlucoseBiosynthesis pathwaysRespirationStarchCelluloseFats and oilsNucleic acids(Storage carbohydrate)(Structural carbohydrate e.g. cell wall)Proteins
43Plant productivityThe biomass of a population of plants is its total mass. This is normally measured as dry mass – as the water content of living organisms varies greatly through out the year.
44AssimilationThe conversion of the glucose produced by photosynthesis into complex components of the plant cell is called assimilation. This process causes an increase in the plants biomass.
45Net assimilationAs some of the sugar produced in photosynthesis is used up during respiration, therefore:Gain in dry mass by photosynthesisLoss in mass caused by respiration=+Net assimilation
46Plant productivityProductivity is the rate at which plants in an ecosystem generate new biomass. It is measured as “units of biomass per unit area per unit time” e.g. grams per square metre per yer.
47Factors affecting plant productivity The rate of photosynthesis (and productivity) is affected by several environmental factors known as limiting factors. These include: temperature, light intensity and carbon dioxide concentration.
48The rate at which photosynthesis proceeds to limited by which ever one of these factors is in short supply. e.g. Light intensity would be the limiting factor on a dull summer day.
49Assessing productivity In order to grow crops efficiently to ensure the maximum yield, farmers/scientists/policy makers need to be able to assess the growing potential of the area.
50The biological yield of an area is the total biomass of plant produced this is useful because tells you the total producing power of the land. The economic yield of an area is the mass of the desired product (e.g. mass of just the barley grains from a barley field)
51The harvest index is calculated using this formula: dry mass of economic yield dry mass of biological yield This gives a useful estimate of what is wasted during the growth of a crop.