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FREEMAN CH 43 - Animal Nutrition 43 KEY CONCEPTS Animals...

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43 KEY CONCEPTS Animals require an array of nutrients to stay healthy, including specific amino acids, vitamins, and elements, as well as organic compounds that have high potential energy. Animals feed on a wide variety of items. In animals that ingest their food, there is usually a close correspondence between the structure of the animal’s mouthparts and the function of those mouthparts in capturing and processing food. Digestion occurs in the digestive tract, which is compartmentalized into organs that have specialized functions in the digestion of food, absorption of nutrients and water, or excretion of wastes. Lack of homeostasis with respect to nutrients such as glucose and cholesterol can cause disease. I f you’re like most people, you probably give a fair amount of thought to the types of food that you eat but little thought to what happens to that food in your digestive tract. As a meal moves through the digestive system, its chemi- cal composition and physical characteristics change dramatical- ly. Structurally and chemically, complex raw materials are broken down into simple components that can be used to build and maintain cells. Large packets of food that enter the mouth must be reduced to monomers that can be absorbed by cells and enter the bloodstream. The digestive system is analogous to an oil refinery or a lumber mill, where bulky, complex raw ma- terials are processed into smaller and more usable products. The types of food that are available to different animals vary widely, however, and food is often in dangerously short supply. Based on these observations, it is logical to predict that animals have a variety of means for obtaining food and that animals are under intense natural selection to make efficient use of the food they have. How do animals get their food, and how do they process it? Which substances in food are used as nutrients, and how do humans and other animals maintain appropriate levels of key nutrients in their bodies? Research on feeding and digestion is fundamental to under- standing many of the most basic aspects of animal anatomy and physiology. But research on animal nutrition has important practical applications as well. For example, this chapter address- es questions about whether certain nutrients can be used to boost athletic performance, and why type II diabetes, heart dis- ease, and other nutrition-related diseases are on the rise in many human populations. Just as plant nutrition is fundamental to the productivity of agricultural and natural ecosystems, nutrition is a basic component of animal health and welfare. Let’s begin with a look at what animals must eat in order to live. Animal Nutrition 977 A young crocodile has just caught a reed frog. Most animals obtain nutrients by ingesting them.
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978 Unit 8 How Animals Work TABLE 43.1 Essential Vitamins (Required by Humans) Name Source in Diet Function Symptoms if Deficient Vitamin legumes, whole grains, potatoes, formation of coenzyme in Krebs cycle beriberi (fatigue, nerve disorders, anemia)
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