1. Animal Nutrition Animals are heterotrophs (cannot make their own food) Food required for –Fuel for cellular work –Organic raw materials for biosynthesis –Essential nutrients those nutrients that an animal cannot make for itself from any raw materials and must be obtained in prefabricated form

2. Homeostasis Importance of energy “budgets” Glucose Regulation –An example of negative feedback –Blood glucose high/stimulate secretion of insulin from pancreas/increase uptake of glucose into liver and muscle cells –Blood glucose low/stimulate secretion of glucagon which promotes breakdown of glycogen stores and releases glucose into the bloodstream

3. Glucose Regulation

4. Caloric Imbalance Undernourishment –Diet deficient in calories –Body starts to break down its own proteins if enough carbs and fats are not present Malnourishment –Consume enough calories but are missing an enough of an essential nutrient in your diet Overnourishment –Excessive intake of calories leads to increases in fat stores and subsequent obesity

5. Obesity Set points Leptin –Hormone produced by adipose tissue –Depresses appetite and increases muscular activity and body heat production Several different genes are believed to play a role in fat homeostasis

6. Essential Nutrients Essential Amino Acids –Eight essential amino acids in adult humans –Similar requirements in most animal species –Protein deficiency can result in retardation of both physical and mental development –Most reliable sources of essential amino acids are meats and other animal products such as eggs and cheese –“Complete” proteins contain all twenty amino acids in the appropriate proportions –Most plant proteins are incomplete / Ex corn – lysine & beans – methionine / mix both to get to “complete”

8. Essential Nutrients, cont’d Essential Fatty Acids –Includes certain unsaturated fatty acids –Deficiencies are rare –Ex: linoleic acid needed to make certain phospholipids

9. Essential Nutrients, cont’d Vitamins –13 vitamins essential to humans –See Table 41.1 in Campbell 7 th ed. p. 851 –Water-soluble vitamins include B complexes (often coenzymes in metabolic pathways) and vitamin C (used in collagen synthesis/anti- oxidant?/deficiency leads to scurvy)

10. Vitamins, cont’d –Fat-soluble include A (eye pigments), D (bone growth), E (anti-oxidant), K (blood clotting) –Easier to overdose on fat soluble vitamins than water soluble vitamins/watch the RDA!!!

11. Essential Nutrients, cont’d Minerals –See table in textbook –Many minerals are enzyme cofactors –Ca/P: important to bone development –S : component of some amino acids –Na/K/Cl : important to acid-base and water balance –I : component of thyroid hormones

12. Food Types and Feeding Mechanisms Herbivores eat autotrophs Carnivore eat other animals Omnivore eat both animals and autotrophs Many animals are opportunistic and will often eat outside their main dietary category if other foods are readily available

13. Feeding Mechanisms Suspension feeders –Sift small food particles from the water –Ex: clams, baleen whales

14. Feeding Mechanisms Substrate feeders –Live in or on their food source –Ex: maggots, leaf-miners

15. Feeding Mechanisms Deposit feeders –A subset of substrate feeders –Ex: earthworms that eat decaying matter ingested along with soil during burrowing

16. Feeding Mechanisms Fluid feeders –Suck nutrient rich fluids from a living host –Ex: aphids, mosquitoes, hummingbirds

17. Feeding Mechanisms Bulk feeders –Eat relatively large pieces of food –Ex: humans, snakes, etc

18. Overview of Food Processing Ingestion –the act of eating Digestion –breaking food down into molecules small enough to absorb –Typically involves both mechanical fragmentation and enzymatic hydrolysis –Proteins to amino acids, carbohydrates to simple sugars, fats to fatty acids and glycerol

19. Overview of Food Processing Absorption –cells take up small molecules such as amino acids and simple sugars Elimination –Removal of undigested material

20. Compartmentalization of Digestion To reduce risk of self-digestion, most animals process food in specialized compartments Intracellular Digestion –Use of food vacuoles as site of digestion in protists after engulfing food by phagocytosis or pinocyctosis –Sponges also use intracellular digestion

21. Intracellular Digestion in a Paramecium

22. Compartmentalization of Digestion Extracellular Digestion –breakdown food outside of cells –Two types: gastrovascular cavity and alimentary canals

23. Gastrovascular cavities Digestive sac with a single opening Secrete digestive enzymes into the cavity, absorb macromolecules, and digest macromolecules intracellularly similar to protists –Ex: cnidarians (hydra) and (platyhelminthes) flatworms

24. Compartmentalization of Digestion Alimentary Canals (Complete Digestive Tracts) –Digestive tubes with both a mouth and an anus –Includes most animals except cnidarians (jellyfish, hydra) and platyhelminthes (tapeworms, planaria)

25. Complete Digestive Tracts (Alimentary Canals)

26. Alimentary Canals of Various Species Note: crop is similar to a stomach & a gizzard is used to mechanically grind food Earthworm –Mouth-pharynx-esophagus-crop-gizzard-intestine- anus Grasshopper –Mouth-foregut (esophagus-crop)-(gastric ceca)- midgut-hindgut (rectum-anus) Bird –Mouth-esophagus-stomach-gizzard-intestine-anus

27. Mammalian Digestive System Oral Cavity –Mechanical breakdown of food –Note how different teeth are adapted for food source –Salivary amylase begins digestion of carbohydrates –Food shaped as a bolus, a ball of food Pharynx –Passageway that leads to trachea or esophagus –Use of epiglottis to cover opening to the trachea so food does not enter the windpipe

28. Mammalian Digestive System Esophagus –Food moves by involuntary muscle contractions (peristalsis) down the esophagus (< 1 min ) Stomach –Functions to store food (2 to 6 hrs) and initiate digestion of proteins (pepsin) –Mucus cells secrete mucus to lubricate and protect the stomach lining from acidic environment

29. Mammalian Digestive System Stomach –Parietal cells secrete acid / stomach pH ~ 2 / activates pepsinogen to pepsin (form of (+) feedback) & aids in breakdown of food –Chief cells secrete pepsinogen –Nutrient rich broth in stomach referred to as acid chyme –Note: presence of sphincter muscles to regulate the movement into and out of the stomach (cardiac sphincter at entrance of stomach, pyloric sphincter at end)

30. Mammalian Digestive System Small Intestine (5-6 hrs) –Duodenum, jejunum, illuem –Major organ of digestion and absorption –Highly invaginated surface (microvilli form on villi) to increase surface area for absorption

31. Small Intestine cont’d Carbohydrate Digestion –Pancreatic amylase converts polysaccharides to disaccharides –Disaccharidases –associated with brush border epithelia of small intestine –maltase, lactase, sucrase –Convert disaccharides to monosaccharides

32. Small Intestine cont’d Protein Digestion –Numerous enzymes assist in the process –Derived from intestinal epithelia or pancreas Trypsin - pancreas Chymotrypsin- pancreas Carboxypeptidases - pancreas Aminopeptidases – intestinal epithelia Dipeptidases – intestinal epithelia

34. Small Intestine cont’d Lipid Digestion –Lipases hydrolyze fat –Emulsification of fats by bile salts Nucleic Acid Digestion –DNA & RNA are digested by nucleases

35. Odds & Ends Chylomicrons – mixture of fats, cholesterol and special proteins that is absorbed by lacteals present in the villi of the small intestine Lacteal – small vessels of the lymphatic system that carry a clear fluid called lymph Hepatic Portal Vessel – carries amino acids and sugars absorbed from the intestinal epithelia directly to the liver Digestion costs between 3 and 30% of the chemical energy contained in a meal

37. Mammalian Digestive System Cecum –T-shaped pouch between small and large intestine –Small in humans (appendix) –Very large in many herbivores Serves as a fermentation chamber to assist in getting more nutrients from food

38. Large Intestine or Colon –Aids in absorption of water (~ 90% of secreted water is reabsorbed by combined action of small & large intestine) –Houses bacteria which synthesize vitamins –Fecal matter passes through the rectum and out the anus

39. Hormonal Regulation of Digestion Gastrin – stimulates gastric motility and secretion of gastric juice Enterogastrones –Secreted by duodenum –Include Secretin & Cholecystokinin –Secretin Secreted by duodenum in response to acid chyme –Cholecystokinin stimulates secretion of stored bile salts (made in the liver but stored in the gall bladder) Recommend review on CD-ROM

40. Adaptations to Vertebrate Digestive Systems A mammal’s dentition is generally correlated with its diet

41. Adaptations to Vertebrate Digestive Systems Herbivores have longer alimentary canals reflecting longer time to digest plant matter

42. Symbiosis and Nutrition Ruminants –Need to digest cellulose/most animals do not have enzymes to digest cellulose and must depend on symbiotic bacteria to do so within a special chamber of the digestive system