2. The material in this slide show is provided free for educational use only. All other forms of storage or reproduction are subject to copyright- please contact the National Marine Aquarium The slide show was designed and produced for the NMA by STEP, the Science Training & Education Partnership T raining & S cience E ducation P artnership www.national-aquarium.co.uk www.step-up-to-science.com

3. Ecosystems & Food Webs: Putting in some numbers

4. Drawing a food web describes the structure of an ecosystem, but does not explain fully how it works

5. We need a more complete understanding of ecosystems for a number of reasons. Examples include ….. Managing resource species, such as fisheries or timber Understanding the role of biological production in climate change

6. What happens within a food-web level Losses along a food chain Summary

7. What happens within a food-web level Losses along a food chain Summary

8. Not all food eaten by an animal is turned into new body tissue - ‘growth’- or is devoted to reproduction

9. In fact, for many animals, very little food contributes to growth Some is indigestible, and is lost as faeces Much food is digested, but then burnt up to provide energy

10. An example: krill feeding on plankton algae 70 milligrammes of algae eaten per day 10 milligrammes - about 15% - is indigestible and lost as faeces A 1-gramme krill needs about 5% of its body mass per day as an energy supply, so it ‘burns up’ 50 milligrammes of food This leaves 10 milligrammes of food that can be used for growth and reproduction

11. 70 milligrammes ‘in’ 50 milligrammes plus 10 milligrammes ‘to waste’ 10 milligrammes to growth = 15% of food eaten

12. A growth rate that is 15% of the food eaten is high To achieve this, the krill is adding 1% of its body mass per day

13. More typically, the ratio between the amount of food eaten and the amount of growth is around 10% The ratio is less for animals which use a lot of energy to stay alive Warm-blooded animals such as mammals typically have ratios less than 5%

14. What happens within a food-web level Losses along a food chain Summary

15. The loss of food material (to provide energy and as indigestible faeces) means that only part of the growth of plants can be eaten by secondary consumers - ‘predators’

17. As the food web becomes more complicated, with longer food chains, less plant production reaches the top- level predators

19. We can contrast two food chains in the Southern Ocean food web

20. Krill converts 15% of algal food to growth Blue whale converts just 4% of krill to growth

21. For 100 units of plankton algal growth... … there are 15 units of new krill growth... … and there are only 0.6 units of new whale growth

22. Now a more complex food chain...

23. Copepod converts 15% of algal food to growth Krill converts 15% of copepod food to growth Fish converts 10% of food to growth Squid converts 10% of food to growth Seal converts 4% of food to growth

24. Now, for 100 units of plankton algal growth... … and there are only 0.001 units of new seal growth 99.999% of the algae eaten by the copepods has been lost

25. Short food chains give an efficient transfer between producers and top- level consumers Long food chains are inefficient

26. What happens within a food-web level Losses along a food chain Summary

27. Much of the food eaten by animals is either converted to energy or lost as faeces Only about 10% of food is converted to growth You have seen that -

28. Because of the low conversion efficiency, much plant production is lost within a food web Long food chains are less efficient than short ones You have seen that -

29. NOTES for USERS The material in this slide show is designed to support the teaching of science at Key Stage 1 A full description of the slide show, and linked activities for students, can be found on the National Marine Aquarium (NMA) web-site: Teachers are free to amend the slide show in whatever way they feel fit, or to use slides in other contexts. However, please note that neither the NMA nor the designers will accept responsibility for modifications, and original material remains copyright of the NMA Individual images used in the slides are copyright of NMA or STEP, except where acknowledged separately The slides have been set up to display as A4 landscape format. If they are incorporated into other slide sequences with different display settings, change in aspect ratio and text location will occur The slide sequence contains the minimum of effects and transitions. However, there are some automated animations, and teachers will wish to make sure that they are familiar with the sequence before use in class Use the PowerPoint notes viewer to obtain additional information for some slides www.justaddh2o.tv www.national-aquarium.co.uk