Chapter 41 Animal Nutrition 1 Chapter 41 Animal Nutrition The Need to Feed Nutrition is the process of food being taken in taken apart and taken up Unlike plants animals must consume food for both energy and the organic molecules used to assemble new molecules cells and tissues Herbivores such as cattle sea slugs and termites dine mainly on plants or algae Carnivores such as sharks hawks and spiders mostly eat other animals Omnivores such as bears don t in fact eat everything but they do regularly consume animals as well as plants or algae Most animals are opportunistic feeders eating foods outside their standard diet when their usual foods aren t available Concept 41 1 an animal s diet must supply chemical energy organic molecules and essential nutrients An adequate diet must satisfy three nutritional needs chemical energy for cellular processes organic building blocks for macromolecules and essential nutrients Chemical energy is used to produce ATP which powers processes ranging from DNA replication and cell division to vision and flight Animals need a source of organic carbon sugar and a source of organic nitrogen protein in order to construct a variety of organic Essential nutrients are materials that an animal s cell requires but cannot synthesize They are obtained from dietary sources and include certain minerals and preassembled organic molecules molecules Essential Nutrients Essential amino acids Essential Fatty Acids Animals require 20 amino acids to make proteins The remaining amino acids that animals are unable to obtain are essential amino acids Some animals have adaptations that help them through periods when their bodies demand extraordinary amounts of protein The essential fatty acids the ones they cannot make are certain fatty acids that contain one or more double bonds and are thus unsaturated Vitamins are organic molecules that have diverse functions and are required in the diet in very small amounts Water soluble vitamins include the B vitamins which are compounds that generally function as coenzymes and vitamin C which is required for the production of connective tissues Fat soluble vitamins are vitamin A which is incorporated into visual pigments of the eye and vitamin K which functions in blood clotting Dietary minerals are inorganic nutrients such as iron and sulfur that are usually required in small amounts Ingesting large amounts of some minerals can upset homeostatic balance and impair health Vitamins Minerals Dietary Deficiencies Deficiencies in Essential Nutrients Insufficient intake of essential nutrients can cause deformities disease and even death A diet that provides insufficient amounts of one or more essential amino acids causes protein deficiency the most common type of malnutrition among humans Under nutrition Assessing Nutritional Needs A diet that fails to provide adequate sources of chemical energy results in under nutrition The body uses up stored carbohydrates and fat and then begins breaking down its own proteins for fuel muscles begin to decrease in size and the brain may become protein deficient Hemochromatosis causes iron buildup in the absence of any abnormal iron consumption or exposure Concept 41 1 Summary an animal s diet must supply chemical energy organic molecules and essential nutrients Food provides animals with energy for ATP production carbon skeletons for biosynthesis and essential nutrients nutrients that must be supplied in preassembled form Essential nutrients include certain amino acids and fatty acids that animals cannot synthesize vitamins which are organic molecules and minerals which are inorganic substances Animals can suffer from two types of malnutrition an inadequate intake of essential nutrients and a deficiency in sources of chemical energy Studies of genetic defects and of disease at the population level help researchers determine human dietary requirements Concept 41 2 the main stages of food processing are ingestion digestion absorption and elimination Ingestion is the act of eating or feeding Suspension Feeders and Filter Feeders Many aquatic animals are suspension feeders which eat small organisms or food particles suspended in the water Filter feeders such as the humpback whale move water through a filtering structure to obtain food Substrate Feeders Fluid Feeders Substrate feeders are animals that live in or on their food source Fluid feeders suck nutrient rich fluid from a living host Chapter 41 Animal Nutrition 2 Bulk Feeders Most animals including humans are bulk feeders which eat relatively large pieces of food Their adaptations include tentacles pincers claws poisonous fangs jaws and teeth that kill their prey or tear off pieces of meat or vegetation Digestion the second stage of food processing food is broken down into molecules small enough for the body to absorb Mechanical digestion such as chewing typically precedes chemical digestion Chemical digestion is necessary because animals cannot directly use the proteins carbohydrates nucleic acids fats and phospholipids in food When large molecules in food are broken down into their components however the animal can use these smaller molecules to assemble the large molecules it needs Chemical digestion by enzymes reverses the process by breaking bonds of macromolecules down with the addition of water The splitting process is called enzymatic hydrolysis Absorption the animal s cells take up absorb small molecules such as amino acids and simple sugars Elimination completes the process as undigested material passes out of the digestive system Digestive Compartments Digestive enzymes hydrolyze the same biological materials such as proteins fats and carbohydrates that make up the bodies of the animal themselves Intracellular Digestion Food vacuoles cellular organelles in which hydrolytic enzymes break down food are the simplest digestive compartments The hydrolysis of food inside vacuoles called intracellular digestion begins after a cell engulfs solid food by phagocytosis or liquid food by pinocytosis Extracellular Digestion In most animal species at least some hydrolysis occurs by extracellular digestion the breakdown of food in compartments that are continuous with the outside of the animal s body Many animals with simple body plans have a digestive compartment with a single opening This pouch called a gastrovascular cavity functions in digestion as well as in the distribution of nutrients throughout the body In contrast with cnidarians and