430 likes | 554 Views
Feeding the World. Do we currently make enough food to feed the world population? 6.8billion 1.2% yearly growth. Photosynthesis. Energy from the sun is essential for food production Plants make their energy through the process of photosynthesis. Photosynthesis:
E N D
Do we currently make enough food to feed the world population? • 6.8billion • 1.2% yearly growth
Photosynthesis • Energy from the sun is essential for food production • Plants make their energy through the process of photosynthesis
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
The Food Chain • Trophic structure – the pattern of feeding relationships within a community • Producers are the base of the food chain • Plants • Phytoplankton
Primary consumers – eat the producers • Insects/some animals • Zooplankton • A.K.A. herbivores – plant eaters
Secondary consumers, tertiary consumers, and quaternary consumers • Carnivors – meat eaters • Why are there not more consumers?
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
How then can there be so many people on the earth? • We are omnivores – eat everything
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
Soil Composition • Soil is composed of layers called soil horizons • Topsoil • Subsoil • Substratum • Soil consists of sand, silt and clay
Top Soil • Humus – dead organic matter • Helps with soil quality and drainage • Most microorganisms and plant roots are found only in this layer
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
Aeration • Roots need water and air
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
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
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
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
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
Macronutrients • The most important is nitrogen • Used to build many proteins and biomolecules like chlorophyll
Nitrogen fixation – the chemical reaction that converts atmospheric nitrogen into a form of nitrogen that plants can use: • Ammonium and Nitrate
Ammonium is made by bacteria in the soil and in root nodules on the plant
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
Plants deficient in nitrogen have stunted growth and usually have yellowing leaves
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
Plants deficient in phosphorus are usually stunted in growth
Potassium • Potassium is the third most important nutrient • Used to activate enzymes needed in respiration and photosynthesis • Also comes from the erosion of rocks
Plants deficient in potassium usually have yellow areas at leaf tips • Plants are also very flimsy and susceptible to root infections
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
Magnesium • Also absorbed in +2 ion form • Essential in the formation of chlorophyll
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
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
Comes from volcanoes and the burning of wood (sulfate is a pollutant that plants remove from the environment)
Fertilizers • As plants consume the nutrients in the soil we have to replace them • Fertilizers replace the missing nutrients
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
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?
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.