How to Use This Presentation

1. How to Use This Presentation • To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” • To advance through the presentation, click the right-arrow key or the space bar. • From the resources slide, click on any resource to see a presentation for that resource. • From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. • You may exit the slide show at any time by pressing the Esc key.

2. Resources Chapter Presentation Image and Activity Bank Transparencies Standardized Test Prep

3. Food and Agriculture Chapter 15 Table of Contents Section 1 Feeding the World Section 2 Crops and Soil Section 3 Animals and Agriculture

4. Section 1 Feeding the World Chapter 15 Objectives • Identifythe major causes of malnutrition. • Comparethe environmental costs of producing different types of food. • Explainhow food distribution problems and drought can lead to famine. • Explainthe importance of the green revolution.

5. Section 1 Feeding the World Chapter 15 Feeding the World • Famine is the widespread malnutrition and starvation in an area due to a shortage of food, usually caused by a catastrophic event. • Modern agriculture practices provide most of the world’s population with enough food to survive. • However, some of these practices can cause environmental damage that eventually makes growing food crops more difficult.

6. Section 1 Feeding the World Chapter 15 Humans and Nutrition • The human body uses food both as a source of energy and as a source of materials for building and maintaining body tissues. • The amount of energy that is available in food is expressed in Calories. One Calorie is equal to 1,000 calories or one kilocalorie. • The major nutrients we get from food are carbohydrates, proteins, and lipids. Our bodies need smaller amounts of vitamins and minerals to remain healthy.

7. Section 1 Feeding the World Chapter 15 Humans and Nutrition

8. Section 1 Feeding the World Chapter 15 Humans and Nutrition • Malnutrition is a disorder of nutrition that results when a person does not consume enough of each of the nutrients that are needed by the human body. • There are many forms of malnutrition. For example, humans need to get 8 essential amino acids from proteins. This is easily done if a variety of foods is eaten. However, in some parts of the world, the only sources of food may be corn and rice, which contain protein, but lacks one of the essential amino acids. Amino acid deficiency can result from such a limited diet.

9. Section 1 Feeding the World Chapter 15 Sources of Nutrition • Diet is the type and amount of food that a person eats. A healthy diet is one that maintains a balance of the right amounts of nutrients, minerals, and vitamins. • The foods produced in the greatest amounts worldwide are grains, plants of the grass family whose seeds are rich in carbohydrates. • Besides eating grains, most people eat fruits, vegetables, and smaller amounts of meats, nuts, and other foods that are rich in fats and proteins.

10. Section 1 Feeding the World Chapter 15 Sources of Nutrition

11. Section 1 Feeding the World Chapter 15 Diets Around the World • People worldwide generally consume the same major nutrients and eat the same basic kinds of food. • But, diets vary by region. • People in more developed countries tend to eat more food and a larger proportion of proteins and fats than people in less developed countries.

12. Section 1 Feeding the World Chapter 15 Diets Around the World

13. Section 1 Feeding the World Chapter 15 The Ecology of Food • As the human population grows, farmland replaces forests and grasslands. • Feeding everyone while maintaining natural ecosystems becomes increasingly difficult. • Different kinds of agriculture have different environmental impacts and different levels of efficiency.

14. Section 1 Feeding the World Chapter 15 Food Efficiency • The efficiency of a given type of agriculture is a measure of the quantity of food produced on a given area of land with limited inputs of energy and resources. • An ideal food crop is one that efficiently produces a large amount of food with little negative impact on the environment.

15. Section 1 Feeding the World Chapter 15 Food Efficiency • On average, more energy, water, and land are used to produced a Calorie of food from animals than to produce a Calorie of food from plants. • Animals that are raised for human use are usually fed plant matter, but because less energy is available at each level on a food chain, only about 10 percent of the energy from the plants gets stored in the animals.

16. Section 1 Feeding the World Chapter 15 Food Efficiency • Thus, a given area of land can usually produce more food for humans when it is used to grow plants than when it is used to raise animals. • The efficiency of raising plants for food is one reason why diets around the world are largely based on plants. • However, meat from animals generally provides more nutrients per gram than most food from plants.

17. Section 1 Feeding the World Chapter 15 Old and New Foods • Researchers hope to improve the efficiency of food production by studying plants and other organisms that have high yield. • Yieldis the amount of crops produced per unit area. • Researchers are interested in organisms that can thrive in various climates and that do not require large amounts of fertilizer, pesticides, or fresh water. Some organisms have been a source of food for centuries, while other sources are just being discovered.

18. Section 1 Feeding the World Chapter 15 World Food Problems • Some people become malnourished because they simply do not get enough food. • More food is needed each year to feed the world’s growing population. • World food production has been increasing for decades, but now food production is not increasing as fast as the human population is increasing.

19. Section 1 Feeding the World Chapter 15 World Food Problems

20. Section 1 Feeding the World Chapter 15 Unequal Distribution • If all the food in the world today were divided equally among the human population, no one would have quite enough food for good health. • But food is not divided equally, and malnutrition is largely the result of poverty. Even in the United States, many poor people suffer from malnutrition. • Wars and political strife can also lead to malnutrition because they interrupt transportation systems.

21. Section 1 Feeding the World Chapter 15 Droughts and Famines • A drought is a prolonged period during which rainfall is below average, and crops grown without irrigation may produce low yields or fail entirely. • A drought is more likely to cause famine in places where most food is grown locally. • If a drought occurs, there may be no seed to plant crops the following year. The effects of a drought can continue for years.

22. Section 1 Feeding the World Chapter 15 Drought and Famines • People in a given area can usually survive one crop failure. They may have saved enough food from previous seasons, or they may have systems for importing food from elsewhere. • But several years of drought cause severe problems for any area of the world. • For example, after a long drought, the soil may be less able to support the production of food crops.

23. Section 1 Feeding the World Chapter 15 The Green Revolution • Worldwide, between 1950 and 1970, increases in crop yields resulted from the use of new crop varieties and the application of modern agriculture techniques. • These changes were called the green revolution. Since the 1950s, the green revolution has changed the lives of millions of people. • However, the green revolution also had some negative effects.

24. Section 1 Feeding the World Chapter 15 The Green Revolution • For example, most new varieties of grain produce large yields only if they receive large amounts of water, fertilizer, and pesticides. In addition, the machinery, irrigation, and chemicals required by new crop varieties can degrade the soil if they are not used properly. • As a result of the overuse of fertilizers and pesticides, yields from green revolution crops are falling. The grain production in the U.S. has decreased since 1990, partly because the amount of water used for irrigation has decreased.

25. Section 1 Feeding the World Chapter 15 The Green Revolution • In addition, the green revolution had a negative impact on subsistence farmers, or farmers who grow only enough food for local use. • Before the green revolution, subsistence farmers worked most of the world’s farms. • But they could not afford the equipment, water, ad chemicals needed to grow new crop varieties.

26. Section 2 Crops and Soil Chapter 15 Objectives • Distinguishbetween traditional and modern agricultural techniques. • Describefertile soil. • Describethe need for soil conservation. • Explainthe benefits and environmental impacts of pesticide use. • Explainwhat is involved in integrated pest management. • Explainhow genetic engineering is used in agriculture.

27. Section 2 Crops and Soil Chapter 15 Crops and Soil • Arable land is farmland that can be used to grow crops. • The Earth has only a limited area of arable land. • But, as the human population continues to grow, the amount of arable land per person decreases.

28. Section 2 Crops and Soil Chapter 15 Agriculture: Traditional • The basic processes of farming include plowing, fertilization, irrigation, and pest control. • Traditionally, plows are pushed by the farmers or pulled by livestock. Plowing helps crops grow by mixing soil nutrients, loosening soil particles, and uprooting weeds. Organic fertilizers, such as manure, are used to enrich soil. While fields are irrigated by water flowing through ditches. • These traditional techniques have been used since the earliest days of farming.

29. Section 2 Crops and Soil Chapter 15 Agriculture: Modern • In most industrialized countries, the basic processes of farming are now carried out using modern agricultural methods. • Machinery powered by fossil fuels is now used to plow the soil and harvest crops. Synthetic chemical fertilizers have replaced manure and plant wastes to fertilize soil. • A variety of overhead sprinklers and drip systems may be used for irrigation. And synthetic chemicals are used to kill pests.

30. Section 2 Crops and Soil Chapter 15 Fertile Soil: The Living Earth • Soil that can support the growth of healthy plants is called fertile soil. • Topsoilis the surface layer of the soil, which is usually richer in organic matter than the subsoil is. • Fertile topsoil is composed of living organisms, rock particles, water, air, and organic matter, such as dead or decomposing organisms. Several layers of soil lie under the topsoil. The bottom layer is bedrock, which is the solid rock from which most soil originally forms.

31. Section 2 Crops and Soil Chapter 15 Fertile Soil: The Living Earth

32. Section 2 Crops and Soil Chapter 15 Fertile Soil: The Living Earth • Most soil forms when rock is broken down into smaller and smaller fragments by wind, water, and chemical weathering. Chemical weathering happens when the minerals in rock react chemically with substances to form new materials. Temperature changes and moisture can also cause rock to crack and break apart. • It can take hundreds or even thousands of years for these geological processes to form a few centimeters of soil.

33. Section 2 Crops and Soil Chapter 15 Fertile Soil: The Living Earth • Other processes also help to produce fertile topsoil. For example, the rock particles supply mineral nutrients to the soil. • Fungi and bacteria live in the soil, and they decompose dead plants as well as organic debris and add more nutrients to the soil. • Earthworms, insects, and other small animals help plants grow by breaking up the soil and allowing air and water into it.

34. Section 2 Crops and Soil Chapter 15 Fertile Soil: The Living Earth

35. Section 2 Crops and Soil Chapter 15 Soil Erosion: A Global Problem • Erosion is a process in which the materials of the Earth’s surface are loosened, dissolved, or worn away and transported from one place to another by a natural agent, such as wind, water, ice, or gravity. • In the U.S., about half of the original topsoil has been lost to erosion in the past 200 years. • Without topsoil, crops cannot be grown. Yet, almost all farming methods increase the rate of soil erosion.

36. Section 2 Crops and Soil Chapter 15 Soil Erosion: A Global Problem

37. Section 2 Crops and Soil Chapter 15 Land Degradation • Land degradation happens when human activity or natural processes damage the land so that it can no longer support the local ecosystem. In areas with dry climates, desertification can occur. • Desertificationis the process by which human activities or climatic changes make arid or semiarid areas more desertlike. • This process is causing some of our arable land to disappear.

38. Section 2 Crops and Soil Chapter 15 Land Degradation • For example, in the past, people who lived in the drier part of the Sahel region in Africa grazed animals, while people in the wetter part of the region planted crops.The grazing animals were moved from place to place to find fresh grass. The cropland was planted for only a few years, and then allowed to lie fallow, or to remain unplanted, for several years. • These methods allowed the land to adequately support the people in the Sahel.

39. Section 2 Crops and Soil Chapter 15 Land Degradation • But the population in the region has grown, and the land is being farmed, grazed, and deforested faster than it can regenerate. Crops are planted too frequently and fallow periods are being shortened or eliminated completely. • As a result, the soil is losing fertility and productivity. Because of overgrazing, the land has fewer plants to hold the topsoil in place. • So, large areas have become desert and can no longer produce food.

40. Section 2 Crops and Soil Chapter 15 Soil Conservation • There are many ways of protecting and managing topsoil and reducing erosion. • Soil usually erodes downhill, and many soil conservation methods are designed to prevent downhill erosion. • For example, soil-retaining terraces can be build across a hillside. On gentler slopes, contour plowing, which consists of plowing across the slope of a hill instead of up and down the slope, can be used.

41. Section 2 Crops and Soil Chapter 15 Soil Conservation • An even more effective method of plowing is leaving strips of vegetation across the hillside instead of plowing the entire slope. • These strips catch soil and water that run down the hill. • Still, many areas of land that have hills are not suited to farming, but may be better used as forest or grazing land.

42. Section 2 Crops and Soil Chapter 15 Soil Conservation • In no-till farming, a crop is harvested without turning the soil over, as in traditional farming. • Later, the seeds of the next crop are planted among the remains of the previous crop. The remains of the first crop hold the soil in place while the new crop develops. • Although this method saves time and reduces soil erosion, it is not suited for all crops. Other disadvantages include soil that is too densely packed and lower crop yields over time.

43. Section 2 Crops and Soil Chapter 15 Enriching the Soil • Soil was traditionally fertilized by adding organic matter that would decompose, adding nutrients to the soil and improving the soil texture. • However, inorganic fertilizers that contain nitrogen, phosphorous, and potassium have changed farming methods. Without them, world food production would be less than half of what it is today. • If erosion occurs in areas fertilized with inorganic materials, waterways may become polluted.

44. Section 2 Crops and Soil Chapter 15 Enriching the Soil • Over the past 50 years, the use of such inorganic fertilizers has increased rapidly.

45. Section 2 Crops and Soil Chapter 15 Enriching the Soil • A modern method of enhancing the soil is to use both organic and inorganic materials by adding compost and chemical fertilizers to the soil. • Compostis a mixture of decomposing organic matter, such as manure and rotting plants, that is used as fertilizer and soil conditioner. • Many cities and industries now compost yard and crop wastes. This compost is then sold to farmers and gardeners, and the process is saving costly land fill space.

46. Section 2 Crops and Soil Chapter 15 Salinization • The accumulation of salts in the soil is known as salinization. • Salinization is a major problem in places that have low rainfall and naturally salty soil. • When water evaporates from irrigated land, salts are left behind. • Salinization can be slowed if irrigation canals are lined to prevent water from seeping into the soil, or if the soil is watered heavily to wash out salts.

47. Section 2 Crops and Soil Chapter 15 Pest Control • Worldwide, pests destroy about one-third of the world’s potential food harvest. • A pest is any organism that occurs where it is not wanted or that occurs in large enough numbers to cause economic damage. • Humans try to control populations of many types of pests, including plants, fungi, insects, and microorganisms.

48. Section 2 Crops and Soil Chapter 15 Pesticides • Many farmers rely on pesticides to produce their crops. • A pesticideis a poison used to destroy pests, such as insects, rodents, or weeds; examples include insecticides, rodenticides, and herbicides. • Pesticides, however, can also harm beneficial plants and insects, wildlife, and even people.

49. Section 2 Crops and Soil Chapter 15 Pesticide Resistance • Over time, spraying large amounts of pesticide to get rid of pests usually makes the pest problem worse. • Pest populations may evolve resistance, the ability to survive exposure to a particular pesticide. • More than 500 species of insects have developed resistance to pesticides since the 1940s.

50. Section 2 Crops and Soil Chapter 15 Human Health Concerns • Pesticides are designed to kill organisms, so they may also be dangerous to humans. • Cancer rates among children in areas where large amounts of pesticides are used on crops are sometimes higher than the national average. • People who apply pesticides need to follow safety guidelines to protect themselves from contact with these chemicals.