04 17 2011 LECTURE 15 Agriculture the science art and practice of cultivating the soil producing crops and raising livestock For most of early history humans survived as foragers or hunter gathers gathering wild plants and hunting animals in their natural environment Around 10000 years ago there was a shift in human endeavor from foraging to farming Why it happened is not known but it appears to have formed the basis of advanced civilization in both the old and new worlds Early Sites of Agriculture Syria Lebanon and Israel The near East the Fertile Crescent of Mesopotamia modern day Iran Iraq Turkey o Archeological sites with plant remnants that date up to 14000 years ago o Early plants wheat barley pea lentil o Early animals goat sheep dogs The Far East rivers hemp The New World o In southeast asia modern day Thailand China along the Yellow and Yangtze o 8000 years ago began cultivating rice millet broomcorn millet rapeseed o there was also evidence of domesticated cattle pigs dogs and poultry o In the New World modern day Mexico and Peru o 12000 to 10000 years ago Tehuacan Valley o Began cultivating domesticating major crops Mexico beans corn tomato peanut chili peppers squash Peru and South America potato cacao Domesticated Plants progenitors Plants that have been domesticated are genetically distinct from their wind Wild plants develop by Natural Selection ensures their survival in the environment Plants are domesticated by artificial selection traits are selected not fo survival but for our own benefit Most domesticated plants could not survive in the wild Cultivated plants Centers of origin regions where many cultivated plants came from From these centers plants and animals were dispersed and spread to other areas of the world by explorers invaders travelers etc Wild ancestors of many domesticated plants still exist they help in the development These wild ancestors are important for maintaining the genetic diversity of crop of new varieties plants Modern agriculture Now that we know how agriculture began lets look at modern day agriculture World food and fiber that sustains the entire population of this planet is produced on just 3 of the plant s land 97 of the land is non crop or non grazing it s tundra desert forest mountain and tropical forest the best land is already used in crop production Agriculture in the U S The land area in the United States is 1 9 billion acres 16 is used as crop land 34 is used for pasture and grazing four major crops are planted on 80 of crop land corn wheat soybeans and hay vegetables fruit and nuts potato rice apples tomato peanuts sugarcane are produced on 7 of the crop land cotton on 4 of the land U S Agriculture There has been a steady increase in agricultural yield per acre in U S crops without any significant increase in new land How can this be o Improved crops varieties higher yield o Improved agricultural practices o Improved pest control resistant cultivars o Tailored fertilization of crops Human Nutrition We eat every day we fulfill our energy needs Like a car that needs gas we need the nutrients in food for energy Daily nutritional needs in human diet are supplied by o Macronutrients required in large amounts o Micronutrients required in small amounts Calories Calorie a measure of energy o The amount of energy required to raise 1 gram of water 1 degree C Food energy measured in kilo calories kcal 1000 calories Dietary guides use the term calories to describe kcal Humans require from 1200 to 3200 calories per day depending on age sex and activity level or person There are three macronutrients they are the fuel needed for cellular respiration Macronutrients o Carbohydrates o Proteins o Fats Carbohydrates o As you recall carbohydrates are composed of C H O o Divided into Monosaccharides The basic building block of all carbohydrates Glucose the most abundant monosaccharide transported into the blood It is metabolized during cellular respiration to produce energy Fructose and galactose are other important monosaccharides Disaccharides Polysaccharides Sucrose table sugar is the most common disaccharide Composed of 2 monosaccharides joined together Glucose fructose sucrose Other disaccharides Lactose milk sugar Maltose found in germinating grains Provide no nutritional value only calories Contain hundreds or thousands of individual sugar units usually glucose aka Complex carbohydrates Starch long glucose chain found stored in plants potato wheat rice beans corn Starch is broken into glucose by enzymes in the saliva Glycogen is the storage form of glucose in the human body Excess glucose is converted into fat Proteins o Fiber a polysaccharide derived from plants Comes from cellulose cell wall of plant cells which is composed of many glucose Not digestible but provides bulk Dietary fiber can be Soluble found in oat reduces cholesterol levels and risk of heart disease Insoluble found in fruit bran vegetables Absorbs water prevents constipation may prevent certain cancers colorectal o Large complex molecules that perform many functions in the body o They are made from smaller building blocks called amino acids o There are 20 diff amino acids that assemble in many ways to make thousands of proteins o Sources meat fish cheese milk egg beans corn whole wheat bread o Cells in the human body can make 11 out of 20 amino acids but there are 9 oatmeal peanut butter soy bean amino acids the body cannot make The 9 are called essential amino acids must come from the diet Cant be stored by the body must constantly be taken in diet o Complete proteins contain all the essential amino acids o Proteins from animal sources are complete o Proteins from plant sources are incomplete they may lack one or two essential amino acids o In order to get all essential amino acids from plant sources it s necessary to combine different protein plant sources Ex Corn and beans complement each other and provide all essential amino acids o Protein digestion Requires digestive enzymes which are also proteins Digestibility is important some proteins such as egg protein cannot be broken down completely even through egg protein is very complete High quality proteins Contain all essential amino acids Are fully digestible Free their amino acids which are absorbed readily Fats o Fats or lipids are composed of C H O o Have a glycerol head hydrophilic and a hydrophobic tail fatty acid o Lipids are insoluble in water o Have a bad reputation cause obesity heart disease etc o Actually