1. Sustainability and interdependence

2. Key areas:
Food supply, plant growth and productivity
Plant and animal breeding by manipulation of heredity
Crop protection
Animal welfare and behavioural indicators of poor welfare
Symbiosis
Social behaviour
Mass extinction, regaining biodiversity and measuring biodiversity
Threats to biodiversity

3. Key area 1: Food supply, plant growth and productivity

4. Food supply
LI:
Describe the problems arising from an increasing human population in terms of food supply.
Describe how agriculture can be used to control plant growth.

5. Food supply The human population in currently growing.
The present human population is:

6. United Nations estimate of how the human population could increase.

7. Feeding 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.

8. Food security Food security is defined as:
Sufficient food must be available at all times
Food security
Quantity
Quality
Access
Food is sufficiently nutritious and varied to provide a balanced diet
People have economic means to obtain the available food

9. Food security: The challenge
Watch these videos Feeding the future and Food security
Get 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.

10. Agricultural production
The earth possesses 75,000 edible plant species, yet we depend on a few to produce 95% of what we eat.

11. Main crop species Cereals Root crops Legumes Maize Potato Rice Cassava
Soya bean
Legumes

12. Improving yields
As 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.

13. 2. 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.

14. Productivity 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 tissues
Undigested food and waste
Maintaining body temperature
Movement

15. As you move a long a food chain, energy is lost between each trophic level and the next.
Cereal plant Farm animal Human
As a result of this loss of energy livestock production generates far less food per area of land than plant production.
90% energy lost
90% energy lost
10% energy passed on
10% energy passed on

16. Shorter food chains have much less loss of energy:
Cereal plant Farm animal Human
Cereal plant Human
90% energy lost
90% energy lost
10% energy passed on
10% energy passed on
10,000 kJ
100 kJ
1,000 kJ
90% energy lost
10,000 kJ
10% energy passed on
1,000 kJ

17. Therefore arable land planted with crops produces far more food than the same land planted with grass to feed livestock.
However, not all land can be
planted with crops. In this
case it is more efficient to
use them for livestock.

18. Plant growth and productivity
LI:
Describe the processes underlying photosynthesis.
Explain the links between photosynthesis and plant productivity.

19. Plant growth: Photosynthesis
Reminder of photosynthesis from National 5: Take a piece of blank paper – discuss the following:
Write the summary word equation for photosynthesis
Name the two stages.
Describe what happens in each stage.
Pass the sheet to the next group. Tick the correct bits and add any corrections.

20. What 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)
Wavelength
Light wave

21. Visible light is made up of a spectrum of different colours.
Each colour of light has
a different wavelength.
Colour in a copy of the visible light spectrum in your jotters.
400 nm nm nm nm

22. The fate of light when it hits a leaf
White light hitting a leaf (or any surface) will be either:
Reflected
White light
Absorbed
Transmitted

23. Light 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.

24. Which 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.

25. Collect 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.

26. violet
blue
green
yellow
orange
red
Colour in the normal spectrum. Then colour in a second copy of the spectrum viewed through the leaf pigments:

27. Spectrum viewed through Chlorophyll
violet
blue
green
yellow
orange
red
The 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.

28. Separation of leaf pigments by thin-layer chromatography
Follow the instructions for the separation of leaf pigments by chromatography practical.

29. Absorption 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

30. An 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.

31. Absorption spectrum
Action spectrum

32. Accessory pigments
The 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.

33. The chloroplast

34. The 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.

35. Capture 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.

36. The 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.

37. Primary electron acceptor
1. Light energy is absorbed by the chlorophyll creating high-energy electrons H+ H+ H+
3. Energy also used to split water
Oxygen
Water
Chlorophyll
2. Electron passed along transport chain, pumping H+ into grana. H+ H+
Hydrogen H+
NADP H+ H+ H+
NADPH
4. 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 enzyme
ADP + Pi ATP

38. Calvin 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.

39. Glyceraldehyde-3-phosphate
3-phospho- glycerate
RuBisCO
3-phospho- glycerate
Glyceraldehyde-3-phosphate

40. Carbon 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.

41. 3. 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.

42. Uses of sugar
The sugar formed during photosynthesis goes onto the following uses:
Glucose
Biosynthesis pathways
Respiration
Starch
Cellulose
Fats and oils
Nucleic acids
(Storage carbohydrate)
(Structural carbohydrate e.g. cell wall)
Proteins

43. Plant productivity
The 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.

44. Assimilation
The 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.

45. Net assimilation
As some of the sugar produced in photosynthesis is used up during respiration, therefore:
Gain in dry mass by photosynthesis
Loss in mass caused by respiration = +
Net assimilation

46. Plant productivity
Productivity 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.

47. Factors 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.

48. The 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.

49. Assessing 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.

50. The 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)

51. The 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.