Lecture 5 - Origins of Agriculture.pptx

NATS1565: Plant Life, Human Life Week 5: Origins of Agriculture Angela Cope [email protected] First, some Reminders: Assignment 2 is due by 11:59pm tonight. Test 1 is in class next week. (starting at 4:10pm on February 12, 90 minutes long.) It will cover the material covered in class, on the lecture sl...

NATS1565: Plant Life, Human Life Week 5: Origins of Agriculture Angela Cope [email protected] First, some Reminders: Assignment 2 is due by 11:59pm tonight. Test 1 is in class next week. (starting at 4:10pm on February 12, 90 minutes long.) It will cover the material covered in class, on the lecture slides. It will be 50 MC questions. Please bring a pencil and your student card. There are no aids allowed. Second, Finishing Up Last Week: We still have to cover: The Sweet potato Cassava True yams Taro The uses of starches Someone asked me last week “how much do I actually have to know about the potato?” The potato is one of the most important tools of empire that has ever existed, it has changed everything about our society. That said, know the main points – about its cultivation, history, and nutritional value. I’ve changed the slides from last week to reflect more clearly what you need to know. Ipomoea batatas, Sweet Potato (Cultivation): It is not related to the white potato. The sweet potato plant is a vine that is propagated vegetatively, like the white potato. The crop requires a long, warm growing season. China dominates the world’s production. It is used as food staple as well as for livestock feed. In the United States, the sweet potato is primarily grown in the South with two major varieties: Drier, starchier, and yellow-fleshed variety is favored in Northern states. Sweeter, moister, deep orange variety is preferred in the South and called yams, (not be confused with the true yam, Dioscorea spp). 4 History: The sweet potato is native to tropical Central and South America; archeological evidence dates its cultivation back at least 8,000 years. It was widely grown as a staple crop in Central America and tropical South America prior to the European arrival in the New World. Columbus discovered the sweet potato on his first voyage to the New World and introduced it to Spain on his return. 5 Sweet Potato Nutrition: Nutritionally, sweet potatoes are: Rich in carbohydrates, including sugars. 50% more calories than white potato. Low in protein. Good sources of minerals and vitamins, especially A and C. 6 Manihot esculenta: Botany and Cultivation: Tall shrub with numerous tuberous roots. Propagated by stem cuttings, none of the root used. Can also be cultivated from seed, giving genetic variation. Roots harvested from 8 months to 2 years. Resistant to many insects and fungal pathogens. Tolerant to a wide range of moisture and soil conditions Needs well drained soils to prevent root rot. Tolerates extended dry periods up to 6 months. 7 This Photo by Unknown Author is licensed under CC BY-NC Cassava – Origin & History: Other names for cassava include manioc, tapioca, yuca, yucca root, and mandioca. Cassava is native to South America, and researchers suggest it was domesticated about 10,000 years ago. The Portuguese first introduced cassava into Africa in the 16th century, and extensive cultivation in many African countries began in the 20th century. Today, Nigeria is the world’s largest cassava producer. Cassava was introduced into South Asia in the early 18th century, and by the 19th century, cassava was widely grown in tropical Asia. 8 Processing Cassava: Cassava varieties are classified as sweet or bitter based on the concentration of hydrocyanic acid (HCN). If not removed, this toxin can cause death by cyanide poisoning. Sweet varieties can be eaten with little preparation; peeling followed by boiling, steaming, or frying Bitter varieties must undergo extensive preparation to detoxify before eating (drying, soaking, grating, draining, and fermenting) Traditional methods of treating the peeled roots vary. In South America, the traditional preparation produces a meal called farinha. Peeled roots are grated and then squeezed through a long, woven basket known as a tipiti. One end of the tipiti is tied to a tree while the other end is tied to a pole, which is pulled to stretch the tipiti. This squeezes out the juice from the grated pulp and eliminates most of the HC N. 9 Cassava Nutrition and Usage: Starch the major nutrient. Very low in protein, 1% or less. Can result in kwashiorkor, protein deficiency. On-going research to improve nutrients. Increased protein levels. Enriched beta-carotene production to prevent vitamin A deficiency. In addition to human food, used for animal feed in several countries Also used for commercial starch production for food, textile, pharmaceuticals, and paper. Tapioca pearls, partly gelatinized cassava starch, for puddings. Cassava chips. 10 True Yams, Dioscorea spp.: Large genus of several hundred species with 10 grown for food. Important dietary staples in many tropical areas. Cultivated for over 5000 years in tropical Africa. Starch the main nutrient with only 2% protein. Important source of sapogenins, steroids, used to make human sex hormones and cortisone. Development of the birth control pill based on diosgenin extracted from yams. Dr. Lamont C. Lindstrom 11 Taro, Colocasia esculenta: Same species as the ornamental garden plant, elephant's ears. Thought to have originated in Southeast Asia and spread throughout the tropics. Cultivated today in wet tropical areas, often under saturated soil conditions. Poi, the traditional dish of the native Hawaiians, prepared from taro corm. Foods also wrapped and cooked in the leaves during a Hawaiian feast or luau. 12 Starch: In Our Collars and in Our Colas: Chemically, starch is composed of thousands of glucose molecules bonded together in chains. Two components of starch, amylose and amylopectin, differ in the structural configuration of their chains. Amylose is an unbranched chain of several hundred to a few thousand glucose units. Amylopectin is a highly branched chain containing between 2,000 and 500,000 glucose units. Although amylopectin is the major component of starch, the ratio of the two forms varies with the species and variety of plant. The two forms of starch also differ in their nutritional benefit. Amylopectin is broken down and absorbed into the bloodstream more rapidly than amylose. The ratio of amylopectin to amylose in foods influences the glycemic 13 In Our Collars and in Our Colas: Starch can be extracted from almost any grain, tuber, or other storage organ, but commercially most starch is extracted from corn, potatoes, and cassava. Starch has many commercial uses in both the food and nonfood industries as: Adhesives. Fillers or coatings. Pharmaceutical industry as a binding and coating. Laundry starch. Sugar-based sweeteners. Fermentation products including alcoholic beverages, industrial solvents, or bioethanol. 14 Origins of Agriculture: Key Concepts, Chapter 11: Agriculture evolved independently in several areas of the world. The earliest evidence of agriculture dates back at least 10,000 years in the Near East, the Far East, and Mesoamerica. Domesticated plants are genetically different from their wild counterparts, and many can no longer survive without 15 human intervention. 16 Fig. 11.4 Evidence of the beginnings of agriculture: 17 Agriculture: The Near East: Middle East, Southwest Asia Fertile Crescent, river valleys of Mesopotamia Iraq, Iran, Syria, Turkey, Jordan, Israel 9000 to 14,000 BP Wheat (einkorn, emmer), barley, pea, lentil Cattle, goats, sheep 18 Wheat: The Staff of Life: Michael Thompson/USDA One of the most widely cultivated cereals. Supplies a major percentage of the nutrient needs of the human population. One of the oldest domesticated plants dating back at least 9,000 years in the Near East. Laid the foundation for Western civilization. Wild wheat species still found in northern Iraq, Iran, and Turkey. 19 Evolution of Wheat: Domesticated wheat arose through hybridization and polyploidy involving species of wheat and closely related goat grass species. Wild species are diploid. Hybridization first produced tetraploid species of wheat. Another hybridization produced hexaploid bread wheat. Crosses occurred naturally. Genetic contributions of goat grasses were a higher protein content and greater tolerance to environmental conditions. Access the text alternative for these images 20 Modern Cultivars: Two widely cultivated wheat species: Triticum aestivum, about 90% of global wheat, used for bread, pastries, breakfast cereal. Triticum durum, about 5 to 8% of global wheat, used for pasta, noodles, and some bread. 21 Nutrients in Wheat: Whole grain wheat is nutrient-rich with an average of 12.9% protein. However, cereals have incomplete proteins and are low in lysine and tryptophan. Whole grain wheat is missing only four essential nutrients: Vitamins A, B12, C, and iodine Most wheat consumed in the United States is refined. Many nutrients, concentrated in the bran and germ, are lost during refining. Table 12.2 Vitamins and Minerals Lost during Refining of Wheat Nutrient Lost (%) Cobalt 88.5 Vitamin E 86.3 Manganese 85.8 Magnesium 84.7 Niacin 80.8 Riboflavin 80.0 Sodium 78.3 Zinc 77.7 Thiamine 77.1 Potassium 77.0 Iron 75.6 Vitamin 71.8 Phosphorus 70.9 Copper 67.9 Calcium 60.0 Panthothenic acid 50.0 Molybdenum 48.0 Chromium 40.0 Selenium 15.9 22 The Rise of Bread: Thousands of types of bread are made by mixing flour with water to make dough. For leavened bread the flour must contain sufficient quantities of gluten for the dough to become elastic. When yeast or other leavening agent is added, the dough rises and, when baked, results in leavened bread. Only wheat and rye have sufficient gluten to produce a leavened bread, and wheat is preferred for its higher gluten content. Egyptians credited with discovering leavened bread using wheat flour almost 4,000 years ago. A new form of wheat that could be threshed without heat led to the discovery of leavened bread. It is assumed that yeast from the air was accidentally introduced into dough prepared from these grains. Alternatively, yeast may have been introduced from beer added for flavour. If the dough was set aside before baking, it would rise and produce a lighter, tastier bread. 23 Domestication of the Cat: Egypt: 4000 years ago Cyprus: Joint burial of human and cat This Photo by Unknown Author is licensed under CC B Protecting stored grain from rodents China 5300 years ago: Cats with C4 isotope from domesticated millet 24 ThisThis Photo Photo by Unknown by Unknown Author Author is licensed is licensed under under CC CC BY-S B The Far East: Rice 11,500 years ago, Yangtze River Valley Millet 8000 years ago, Yellow River Valley Silkworm 5000 years ago Larger cocoons, faster growth and reproduction, improved digestion, tolerate handling and crowding, loss of predator avoidance, inability to fly Horse 5,500 years ago Plains of Central Asia, Kazakhstan Tooth wear indicates bits and bridles Mare’s milk residue in pottery remains 25 Rice: Food for Billions Rice feeds more people worldwide than any other crop. Over 2 billion people, mainly in Asia, rely on rice as a dietary staple. Rice cultivation dates back 8,000 to 9,000 years in China. Separate domestication may have occurred in northern India. Oryza sativa is the main cultivated rice in most areas of the world. Oryza sativa is believed26 to Rice: Oryza sativa The rice plant is a multi-stalked annual with the typical vegetative appearance of grasses. Air chambers in the stem permit the diffusion of air from stomata in the leaves through the stem and into the roots. This adaptation permits rice to survive in flooded or waterlogged soils. 27 A Plant for Flooded Fields: Although rice can be grown like other cereals without flooding, in most areas of the world it is cultivated in flooded fields, called paddies. The paddies are diked with earthen dams and filled by rain or irrigation. Young seedlings are started in seedbeds and then transplanted, into the paddies. When the grains are almost mature, the fields are drained to prepare for harvesting. One weed in the rice paddies is known to be beneficial. Azolla, a small, aquatic fern that is inhabited by a symbiotic nitrogen-fixing cyanobacterium, Anabaena azollae. Nitrogen-fixing species are able to convert atmospheric nitrogen into a form that can be used by plants. This natural source of nitrogen reduces the need for fertilizers. 28 Domestication of the Dog: Doglike animals were in Europe and Siberia 30,000 years ago – triple the amount of time we have had domesticated crops. Ancestral wolf may be extinct. Wolf ancestor was likely from Eastern Eurasia. Characteristics common to domesticated species: White spotted coats Floppy ears Juvenile appearance Smaller body size Reduced fear of humans 29 Domestication of the Chicken Jungle fowl Southeast Asia 3,500 years ago Drawn to dryland rice fields First domesticated as a revered or cultural symbol Not used as livestock until 1700 years ago when brought to the Mediterranean area 30 The New World: Mesoamerica Tehuacan Valley in the Central Mexico Highlands: 5,500 years ago Squash, avocado, corn, gourd, amaranth, beans, chili peppers, tomato, peanut, guava Turkey, dog, Muscovy duck Guila Naquitz, Oaxaca, southern Mexico 31 Preserved Corncobs from the Tehuacan Valley in Mexico: Donald Hulbert/Smithsonian Institution Access the text alternative for these images 32 Ancestry of Corn: Teosinte Corn evolve from a species of teosinte, wild grasses native to Mexico and Central America. Some characteristics of teosintes are similar to corn, but others are different. Molecular data has shown that one species of teosinte, Zea mays subspecies parviglumis is almost indistinguishable from corn and confirms that this species is the ancestor of modern corn. Hugh Iltis Additional molecular evidence suggests that five major gene changes could have resulted in the evolution of corn from teosinte. 33 Corn/Maize: A New World Crop: When the Europeans came upon the New World late in the 15th century, the dietary staple was a cereal unknown to them. It was called maize by the indigenous peoples, and later named Zea mays by Linnaeus. An unusual cereal: Corn is much larger than other cereals. The grains (kernels) are naked. The entire ear is tightly covered with husks. Under natural conditions, husks prevent seed dispersal, which means that corn is poorly 34 Types of Corn: USDA Several types of corn can be characterized by the nature of the starch present in the endosperm. Starch has two components, amylose and amylopectin. Hard starch has more amylose than soft starch. Dent corn is the most widely grown in the United States. It has soft starch in the center which forms a dent on drying. Dent corn is used for animal feed, corn starch, and corn meal. Thousands of cultivars available. 35 Value of Corn: Majority of corn is used for animal feed. Only a small part of the harvest is eaten as a vegetable. Much is processed for food products or industrial applications, including biofuel production. Corn starch, corn meal, corn flour, corn oil, and corn syrup are found in thousands of prepared foods. Industrial uses of corn starch include laundry 36 The New World: Central and South: Central and South America (Ecuador coast): 9-10,000 years ago Squash South America: Chili peppers Llama, alpaca, vicuna, guinea pig 37 The New World: North North America (Eastern half of continent): 4,000 years ago Sunflower Marsh elder Goosefoot Gourd 38