Chapter 15 Notes
Section 1 Objectives:
Identify the major causes of malnutrition.
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Malnutrition is a condition that occurs when people do not consume enough food.
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Humans need eight essential amino acids from protein.
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However, in some parts of the world the only sources of food may be corn and rice. These foods lack one essential amino acid and can cause amino acid deficiency.
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Sources of nutrition come from a person’s diet. A diet is the type and amount of food he or she eats.
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A healthy diet maintains a balance of the right amounts of nutrients, minerals and vitamins.
Compare the environmental costs of producing different types of food.
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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.
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Researchers hope to improve the efficiency of food production by studying plants and other organisms that have high yield —the amount of food that can be produced in a given area.
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Plants are less expensive than animals and meat to produce.
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Researchers are interested in organisms that can thrive in various climates and that do not require large amounts of fertilizer, pesticides, or fresh water.
Explain how food distribution problems and drought can lead to famine.
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More food is needed each year to feed the world’s growing population.
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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.
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And malnutrition is largely the result of poverty.
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Wars and political strife can also lead to malnutrition because they interrupt transportation systems
Explain the importance of the green revolution.
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Worldwide, increases in crop yields resulted from the use of new crop varieties and the application of modern agricultural techniques. These changes were called the green revolution
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However, the green revolution also had some negative effects. 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.
Section 2 Objectives:
Distinguish between traditional and modern agricultural techniques.
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The Earth has only a limited area of arable land that can be used to grow crops. As our human population continues to grow, the amount of arable land per person decreases.
Traditional
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The basic processes of farming include plowing, fertilization, irrigation, and pest control.
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Plowing helps crops grow by mixing soil nutrients, loosening soil particles, and uprooting weeds.
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Organic fertilizers, such as manure, are used to enrich the soil so that plants grow strong and healthy.
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Fields are irrigated by water flowing through ditches. Weeds are removed by hand or machine.
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These traditional techniques have been used since the earliest days of farming, centuries before tractors and pesticides were invented.
Modern
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In most industrialized countries, the basic processes of farming are now carried out using modern agricultural methods.
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Machinery powered by fossil fuels is now used to plow the soil and harvest crops.
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Synthetic chemical fertilizers are now used instead of manue and plant wastes to fertilize soil.
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A variety of overhead sprinklers and drip systems may be used for irrigation.
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And synthetic chemicals are used to kill pests.
Describe fertile soil.
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Soil that can support the growth of healthy plants is called fertile soil.
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Plant roots grow in the surface layer of 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.
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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.
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Earthworms, insects, and other small animals help plants grow by breaking up the soil and allowing air and water into it.
Describe the need for soil conservation.
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There are many ways of protecting and managing topsoil and reducing erosion.
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Soil usually erodes downhill, and many soil conservation methods are designed to prevent downhill erosion.
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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.
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In traditional farming, after a crop is harvested, the soil is plowed to turn it over and bury the remains of the harvested plants. In no-till farming, a crop is harvested without turning over the soil. 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.
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No-till farming saves time compared with conventional methods.
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This method can also reduce soil erosion to one-tenth of the erosion caused by traditional methods.
Explain the benefits and environmental impacts of pesticide use.
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Pesticides are chemicals used to kill insects, weeds, and other crop pests. During the last 50 years, scientists invented many new pesticides.
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The pesticides were so effective that farmers began to rely on them almost completely to protect their crops from pests.
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The problem of pesticides harming people and other organisms is especially serious with pesticides that are persistent. A pesticide is persistent if it does not break down easily or quickly in the environment.
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Persistent pesticides do not break down rapidly into harmless chemicals when they enter the environment. As a result, they accumulate in the water and soil.
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Some persistent pesticides have been banned in the United States, but many of them remain in the environment for many years. DDT, a persistent pesticide banned in the United States in the 1970s, can still be detected in the environment and has even been found in women’s breast milk.
Explain what is involved in integrated pest management.
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Integrated pest management is a modern method of controlling pests on crops.
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The goal of integrated pest management is not to eliminate pest populations but to reduce pest damage to a level that causes minimal economic damage.
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A different management program is developed for each crop. The program can include a mix of farming methods, biological pest control, and chemical pest control.
Explain how genetic engineering is used in agriculture.
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Plant breeding has been used since agriculture began. Farmers select the plants that have the tastiest tomatoes and the least least damage. They save seeds from these plants to use in planting the next crop.
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A faster way of creating the same result is to use genetic engineering, the technology in which genetic material in a living cell is modified for medical or industrial use.
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Genetic engineering involves isolating genes from one organism and implanting them into another.
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Scientists may use genetic engineering to transfer desirable traits, such as resistance to certain pests.
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The plants that result from genetic engineering are called genetically modified (GM) plants
Section 3 Objectives:
Explain how overharvesting affects the supply of aquatic organisms used for food.
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Catching or removing from a population more organisms than the population can replace is called overharvesting.
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Many governments are now trying to stop overharvesting. They have created no-fishing zones, so that fish populations can recover.
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Research shows that fishing in areas surrounding no-fishing zones improves after no-fishing zones have existed for a few years. In some areas of the world, such restrictions are necessary if fish markets are to prosper.
Describe the current role of aquaculture in providing seafood.
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Fish and other aquatic organisms provide up to 20 percent of the animal protein consumed worldwide. But overharvesting is reducing the amount of fish and other organisms in the world’s oceans.
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One solution to this problem may be a rapid increase aquaculture, the raising of aquatic organisms for human use or consumption
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There are a number of different methods of aquaculture. An oyster farm represents one such method.
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The most common method is known as a fish farm. Fish farms generally consist of many individual ponds that each contain fish at a specific stage of development. Clean water is circulated through the ponds and brings in oxygen while sweeping away carbon dioxide and fecal wastes. The fish grow to maturity in the ponds and then are harvested.
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Another type of aquaculture operation is known as a ranch.
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In this method, fish such as salmon are raised until they reach a certain age and then are released. The salmon, for example, migrate downstream to the ocean, where they live until adulthood.
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When they are mature, the fish return to their birthplace to reproduce. When they return, they are captured and harvested.
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Today, most of the catfish, oysters, salmon, crayfish, and rainbow trout eaten in the United States are the products of aquaculture.
Describe the importance of livestock in providing food and other products.
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Domesticated animals that are raised to be used on a farm or ranch or to be sold for profit are called livestock.
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Large livestock operations, such as the pig farm produce most of the meat that is consumed in developed countries.
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Meat production per person has increased worldwide since 1950.
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Livestock are also important in developing countries. In these countries, livestock not only provide leather, wool, eggs and meat, but also serve many other functions.
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Some livestock are used as draft animals to pull carts and plows. Other livestock provide manure as the main source of plant fertilizer or as a fuel for cooking.
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