Feeding the World

1. Feeding the World

2. Do we currently make enough food to feed the world population? • 6.8billion • 1.2% yearly growth

4. Photosynthesis • Energy from the sun is essential for food production • Plants make their energy through the process of photosynthesis

5. Photosynthesis: CO2 + H2O sunlight C6H12O6 + 6O2 • The energy that plants make can then be passed along to other species by ingestion • i.e. plants make starches which other animals ingest and metabolize

6. The Food Chain • Trophic structure – the pattern of feeding relationships within a community • Producers are the base of the food chain • Plants • Phytoplankton

7. Primary consumers – eat the producers • Insects/some animals • Zooplankton • A.K.A. herbivores – plant eaters

8. Secondary consumers, tertiary consumers, and quaternary consumers • Carnivors – meat eaters • Why are there not more consumers?

9. Limit to food supply • Only about 10% of the energy in an organism is passed on to the consumer • So plants get 100% of their energy from the sun • The grasshopper gets only 10% of this energy so it needs to eat 10 plants to have the same energy

11. How then can there be so many people on the earth? • We are omnivores – eat everything

12. Decomposers • Any organism that dies before it is eaten then becomes subject to decomposition • Fungi, microorganisms, insects, and earthworms all take dead material and break it down into simpler molecules • Decomposers add nutrients back into the soil for plants to use later

13. Soil Composition • Soil is composed of layers called soil horizons • Topsoil • Subsoil • Substratum • Soil consists of sand, silt and clay

14. Top Soil • Humus – dead organic matter • Helps with soil quality and drainage • Most microorganisms and plant roots are found only in this layer

15. Substratum is the lowest phase where the solid rock of the earth’s crust is slowly turning into soil • Subsoil is above the substratum and consists mostly of clay

16. Aeration • Roots need water and air

17. The more porous a soil the better water flows through it • Percolation – water flowing through soil • Leaching – as water flows through soil it can carry away nutrients with it

18. Most nutrients are positive ions • Soil particles and humus generally contain negative carboxylates and phenolates • This helps keep the nutrients in the soil so water will not wash them away

20. Soil pH • Carbon dioxide is the largest contributor to soil pH • CO2 comes from plant root respiration and the decomposition of humus • This results in a build up of hydronium • Soil pH can range from 4-7 • But this is not all bad…soil need to be a little acidic for nutrients

21. Hydronium ion production is important to plants

22. Plants need nutrients • Plants can not live on sunshine alone, they need certain types of elements to sustain life. • Macronutrients – nutrients needed in large quantities • Micronutrients – nutrients needed in very small quantities

24. Micronutrients are necessary for plants to grow. • Deficiencies rarely occur since plants need so little • Seeds can contain some of the trace elements in sufficient supply to last a lifetime

25. Macronutrients • The most important is nitrogen • Used to build many proteins and biomolecules like chlorophyll

26. Nitrogen fixation – the chemical reaction that converts atmospheric nitrogen into a form of nitrogen that plants can use: • Ammonium and Nitrate

27. Ammonium is made by bacteria in the soil and in root nodules on the plant

28. The nodules are only found in certain plant species • Peas, beans, alfalfa, and clover • These plants can provide ammonium for themselves and other plants • These plants are collectively called the nitrogen fixers

29. Nitrate comes from the atmosphere

30. Plants deficient in nitrogen have stunted growth and usually have yellowing leaves

31. Phosphorus • The next essential nutrient is phosphorus • Very important in building biomolecules as well as energy carriers like ATP • Phosphorus usually comes from the erosion of rocks

32. Plants deficient in phosphorus are usually stunted in growth

33. Potassium • Potassium is the third most important nutrient • Used to activate enzymes needed in respiration and photosynthesis • Also comes from the erosion of rocks

34. Plants deficient in potassium usually have yellow areas at leaf tips • Plants are also very flimsy and susceptible to root infections

35. Calcium • Calcium is used in cell walls • Absorbed as the +2 ion and is fairly immobile in plants • Deficiencies occur at newly growing areas of roots and stems, and usually result in twists and misshapen areas

36. Magnesium • Also absorbed in +2 ion form • Essential in the formation of chlorophyll

37. Cells deficient in magnesium will have yellow spots where chlorophyll is not produced • Chlorosis – the collective term for a plant deficient in either nitrogen, magnesium, or iron

38. Sulfur • From the negatively charged sulfate ion • SO42- • Used in methionine and cysteine (two very important amino acids) • Also used in Coenzyme A, an enzyme used in respiration and the synthesis and breakdown of fatty acids and vitamins

39. Comes from volcanoes and the burning of wood (sulfate is a pollutant that plants remove from the environment)

40. Fertilizers • As plants consume the nutrients in the soil we have to replace them • Fertilizers replace the missing nutrients

41. Straight fertilizer – contains only one nutrient • Mixed fertilizer – contains N, P, K and rated by their percent abundance in the fertilizer • 6-12-12 • 30-15-6

42. Compost generally has a much lower NPK rating but helps to aerate the soil and retain the nutrients • The usual NPK for compost ranges from • 0.5-0.5-0.5 to 4-4-4 • So if the NPK rating of compost is so low why do some people consider it the better fertilizer?

43. On Tuesday – Discussion of food crop production • Genetic engineered foods • Organic vs commercial • Thursday – lecture over the above discussion material • New homework is available today.