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2485 - Lec 19.docx

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School
Western University
Department
Biology
Course
Biology 2485B
Professor
Ben Rubin
Semester
Winter

Description
Lec 19 March 21, 2014 Racing to feed the world • Intensification – more productivity per unit hectare in agriculture  o Led to a greater jump in population • Extensification – expanding the amount of land for productivity Racing to feed the world • India grain production o Total production has increased greatly – fast growing • Production per person has kept up with population growth o Gone from importing grain to exporting • World consumption = 2000 cal/day o Developing countries consume 25% more calories per capita • World increase in production by 250%   Diet choice  • Some diets require a lot more land than others o Beef vs. chickens • Beef requires 20Kg feed input for 1 Kg • Chicken requires 2.8 Kg feed input for 1 Kg The green revolution • Technology o Varieties  o Irrigation o Fertilization o Pest control o Mechanization • Developed these technologies and exported around the world Haber­bosch process • N2 + 3H2  ▯NH3 • At 20 MPa, 400 C • Very energy intensive Fertilizer • Contaminates water • Causes Eutrophication ­ hypoxia • Nitrous oxides released in water Pesticides • Organochlorides – persistent; used in 1942 as insecticides o Registered in Canada – bioaccumalative effects  DDT is banned  • Organophoshates non­persistent – degrade on exposure to sunlight, water.   o Highly toxic – dangerous to applicators Malathion used for mosquito  control (and other purposes) • Carbamates – used in 1930s and large scale in 1950s o Discontinued in 1964 for less toxic means o Non­persistent – toxic to birds and fish • Pyrethroids – least toxic than organophosphates and carbamates o Raid, ant and bee killers o Toxic to aquatic species • Phenoxy acids ­ in 2,4­D broadle
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