1. Land, water and bees – don’t take us for granted Land and water

2. How many people are alive in the world today? 7 000 000 000 + … that’s more than seven billion. World population

3. World population growth Source: https://commons.wikimedia.org/wiki/File:Population_curve.svg, based on data from estimates at census.gov (https://web.archive.org/web/20061231163421/http://www.census.gov/ipc/www/worldhis.html).

4. World population growth Source: https://commons.wikimedia.org/wiki/File:Population_curve.svg, based on data from estimates at census.gov (https://web.archive.org/web/20061231163421/http://www.census.gov/ipc/www/worldhis.html).

5. World population growth Look at the graph and: estimate what the population size might be by the year 2025. suggest why world population increased from the end of the 18th century and grew more sharply from about 1920. suggest what caused the two slowdowns in growth of the world population in the 20 th century.

6. Food security Every day there are 200 000 more mouths around the world to feed. In some parts of the world the population is growing fast, in other areas it is stable. Food security exists when all people, at all times, have physical and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy life. (World Food Summit, 1996)

7. What do we need for food security? Resources must be shared between everyone in the population if we are all going to survive. What are the resources we need?

8. Are there enough resources to go around? ▪70% of the world’s fresh water supply is used in farming. ▪40% of the world’s farmland is too poor to grow very much. ▪Land the size of a football pitch is lost to farming every second. Resources

9. Photo: Dirk Ercken/Shutterstock.com

10. Water is vital in agriculture, but it is often wasted, and can carry nutrients out of the soil (leaching) and deposit excess fertiliser and pesticide in rivers and groundwater (run-off). Photo: Cecilia Lim H M./Shutterstock.com Water in agriculture

11. Hydroponics is a method of growing plants without soil. In place of soil, plants are grown in water containing nutrients. A material base supports their root system. The plants produced usually grow fast and are healthy because conditions are carefully controlled. In ancient Greek, hydros means water and ponos means work. Water in agriculture

12. Photo: pan_kung/Shutterstock.com Water in agriculture Many scientists think that hydroponics could help to feed our growing population and could also save water.

13. There are many different ways of setting up a hydroponic system and many different plants that can be grown. Plants also need light and air to grow, but these are easy to provide and so a hydroponic unit can be set up anywhere. Hydroponic units can be built in places where crops would normally never grow – in old factories and warehouses, or even underground. A hydroponic unit on a window sill can provide a continuous supply of fresh salad for a family. Hydroponic systems

14. Photo: KYTan/Shutterstock.com Hydroponic systems

15. A high-tech hydroponic unit is expensive to set up and to run, but hydroponic growing has advantages that eventually make up for the high start-up costs. More simple methods can be used too. There is no soil to carry diseases, and pests can be controlled within the unit. Plants can be grown closer together or even in vertical layers, saving space. Hydroponic systems

16. What do plants need to grow well? In an investigation, we call these variables. A variable is anything that can change and be measured. There are different types of variables: independent, dependent and control variables. Discuss how you might investigate what plants need to grow well, identifying the variables you would need to consider. Practical activity: variables

17. You will be given some water samples containing different nutrients to use in your hydroponic unit. Plants need several nutrients for good growth. One water sample contains all of these nutrients. In each of the other samples, one nutrient is missing. How can you use the samples to investigate the importance of each nutrient in plant growth? Practical activity: nutrients

18. Cut the top off the bottle. Fill the bottle with nutrient solution. You can put a wick in the neck of the bottle. Lift a seedling by the plug of growing medium and gently put it into the top. Practical activity: bottle unit

19. Data are observations or measurements collected in investigations. Plan how you will record and present the data before you start your experiment. Can you suggest how data from your hydroponics experiment could be recorded to help you draw conclusions? Each group should look at other groups’ data and suggest how to present findings. Practical activity: handling data

20. Clips of a plant scientist and of students running a hydroponics project: https://thecrunch.wellcome.ac.uk/schools Underground hydroponics (report from the Daily Telegraph) https://www.youtube.com/watch?v=xFL_u3qk73 U Links to video