environmental science chapter 14 (pgs 214 – 229) chapter 14: feeding the world
TRANSCRIPT
Section 14.1: “Human Nutrition”
Humans need energy for growth, movement and repair.
Get energy by eating food.Must also consume nutrients to maintain
health.2 types of nutrients:
1. Macronutrients 2. Micronutrients
Macronutrients: provide energy for the body. Measured in kilocalories (kcal) = Calories Number = how much energy food provides. Carbohydrates, proteins, and fats
Micronutrients: provide small amounts of chemicals needed in biochemical reactions.
Macronutrients- Carbohydrates
Carbohydrates-compound made of carbon, hydrogen, and oxygen in 1:2:1 ratio.
2 main types: 1. Sugars- small and simple; absorbed quickly; provide
immediate energy. 2. Starches- larger and complex; steady, long-lasting
energy.4 cal/gramSources: fruits, vegetables, bread, grains.
Function: primary source of energy (starch, glycogen). Only source of energy for the brainProtection (chitin-exoskeleton).Structural elements (cell wall)
Cellulose helps move food along your digestive tract (yay fiber!).
Macronutrients - Protein
Protein- compound made of amino acids; provide body with materials to make blood, muscle, etc; provide energy; carry other structures; serve immune function. Must have nitrogen to make proteins (amino acids
contain nitrogen).4 cal/ gram20 amino acids
12 can be made by human body. 8 are Essential Amino Acids- must be obtained from
food.
Macronutrients - Protein
Sources: food from animals (meats, eggs, dairy); grains (wheat, rice, corn); legumes (peas, beans, peanuts).
Combine foods to get all 8 essential amino acids.
Macronutrients - Protein
Functions: Form structural parts of cell. Carry other structures (hemoglobin) Protection from disease (antibodies) Speed up chemical reactions (enzymes) Chemical messengers (hormones) Control traffic in and out of cell (cell membrane)
Macronutrients - Fats
Lipid- 3 long chains of fatty acids; component of cell membranes, protective function, energy storage function.
Solid lipids- fats (butter and lard)Liquid lipids – oils 9 cal/ gram
Macronutrients - Fats
Saturated vs. Unsaturated Fats Saturated Fat-maximum number of hydrogens in the
chain; can’t fit any more Saturated fats are more solid at room temperature. Bad for your heart Hydrogenated-worst for your heart; unsaturated fats
pumped full of hydrogen. Unsaturated Fat-not full of hydrogen; “crooked”.
Liquid at room temperature. Good for your heart.
Sources: dairy, meat, avocado, nuts, eggs, etc.
Vitamins and Minerals
Micronutrients; play role in reactions that release energy.
All can be obtained from plants.Vitamins: A, B, C, D, E, K
Some are water soluble (excess excreted in urine) while others are fat soluble (extra is stored in fat-can have TOO MUCH).
Minerals: calcium, zinc, magnesium, iron, etc. Also can have too much or not enough.
Vitamins and Minerals
Malnutrition-lack of a specific type of nutrient in the diet. Can also result from inability to absorb or use a
nutrient even if you are eating enough of it.
Section 14.2: World Food Supply
Our food supplies have increased.Why are so many starving?
1. Food increase due to advances in agricultural practices and crop plants.
2. Food is traded and the price is driven by economic factors.
The Green Revolution
Began in 1960s when new strains of wheat and rice were developed. New varieties more responsive to fertilizers and
irrigation, better resistance to disease, faster growth, and can adapt to variety of climates.
High crop yields.Use modern methods to harvest more
efficiently.Resulted in more food without increasing the
amount of farmland.
Problems: Developing nations not have enough water to
maintain new crops. Not have money for fertilizer or modern machinery or
fuel to run them.
Cash Crops
Cash Crop-crop grown for purpose of sale. Get higher prices by exporting than by selling to local
people.Problem:
Income from sale of cash crops used to buy weapons and support political leaders that help the landowners.
Food from the Water
Fish and other sea animals.Estimated that oceans can provide 100
million tons of food per year. Reached this in 1989-we now exceed this limit and are
starting to see the effects. Quantities of fish are beginning to drop.
Alternative: Aquaculture-commercial production of fish in a
controlled, maintained environment. Produces 85% of mollusks (clams, oysters, etc) eaten
in US.
Section 14.3: Modern Farming Techniques
Agriculture used to involve a lot of labor (preparing soil, planting seed, maintaining crops, harvesting, etc).
Middle of 20th century-began to use machines powered by fossil fuels Called “Industrialized Agriculture” Efficient and productive Require large amount of energy, pesticides, fertilizers. Often run by corporations (agribuisinesses).
Use of pesticides Increase in resistant insects and other pests. 1992-California white fly infestation DDT and decline in bald eagle population
Monoculture Farms growing only the 1 or 2 crops that bring in the
most money. Crops genetically identical = more vulnerable to
disease Soil depleted of minerals = soil loses ability to
produce healthy crop.
New grains Not adapted to local conditions Looking to use local grains in many areas Ex: quinoa – grows better than wheat or rice in
mountainous areas, high in protein, can be made into flour, cereal, beverages and livestock feed.
Section 14.4: Sustainable Agriculture
Modern agriculture has resulted in: soil erosion, deforestation, desertification, hunger, war, and environmental damage.
Sustainable agriculture-called regenerative farming; based on crop rotation, reduced soil erosion, pest management, and minimal use of soil additives.
Crop Rotation
Crop Rotation- changing the type of crop grown in an area on a regular cycle. Usually 1 to 6 years per cycle
Prevent soil from becoming depleted of nutrients (nitrogen).
Avoid use of synthetic fertilizers.Cover Crop- nonfood plants grown between
grown seasons on land usually left empty. Restore nitrogen to the soil and help to reduce erosion
Reducing Erosion
Erosion- process where soil is lost, transported, and reformed.
Caused by wind and flowing water.When topsoil removed, loss of nutrients can make
area useless for farming.Can be reduced by irrigation and soil
management. Irrigation-watering of fields; use systems that deliver less
water, but directly to the roots reduces erosion. Tilling-turning the soil so lower layers are brought to the
surface. Destroys weeds and other pests, brings nutrients to the
surface, improves drainage, and aerates the soil. Wastes water, uses energy, can increase erosion.
Pest Management
Integrated Pest Management (IPM)Reduce pesticide use by 90%Use natural predators to manage pests (ex:
wasps, ladybugs, viruses and bacteria, etc)