1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 41 Animal Nutrition

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: The Need to Feed Every meal reminds us that we are heterotrophs, dependent on a regular supply of food In general, animals fall into three categories: – Herbivores eat mainly autotrophs (plants and algae) – Carnivores eat other animals – Omnivores regularly consume animals as well as plants or algal matter

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4. An adequate diet must satisfy three needs: – Fuel for all cellular work – Organic raw materials for biosynthesis – Essential nutrients, substances that the animal cannot make for itself Main feeding mechanisms: suspension feeding, substrate feeding, fluid feeding, bulk feeding

5. LE 41-2a Baleen

6. LE 41-2b Caterpillar Feces

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Video: Lobster Mouth Parts Video: Lobster Mouth Parts Video: Shark Eating a Seal Video: Shark Eating a Seal

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 41.1: Homeostatic mechanisms manage an animal ’ s energy budget Nearly all of an animal’s ATP generation is based on oxidation of energy-rich molecules: carbohydrates, proteins, and fats

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glucose Regulation as an Example of Homeostasis Animals store excess calories as glycogen in the liver and muscles and as fat Glucose is a major fuel for cells Hormones regulate glucose metabolism When fewer calories are taken in than are expended, fuel is taken from storage and oxidized

10. LE 41-3 STIMULUS: Blood glucose level rises after eating. STIMULUS: Blood glucose level drops below set point. Homeostasis: 90 mg glucose/ 100 mL blood

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Caloric Imbalance Undernourishment occurs in animals when their diets are chronically deficient in calories Overnourishment, or obesity, results from excessive intake, with excess stored as fat

12. LE 41-4 100 µm

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Obesity as a Human Health Problem The World Health Organization now recognizes obesity as a major global health problem Obesity contributes to a number of health problems, including diabetes, cardiovascular disease, and colon and breast cancer

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Researchers have discovered several of the mechanisms that help regulate body weight Over the long term, homeostatic mechanisms are feedback circuits that control the body’s storage and metabolism of fat Hormones regulate long-term and short-term appetite by affecting a “satiety center” in the brain

15. LE 41-5 Leptin PYY Insulin Ghrelin

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The complexity of weight control in humans is evident from studies of the hormone leptin Mice that inherit a defect in the gene for leptin become very obese

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18. Obesity and Evolution The problem of maintaining weight partly stems from our evolutionary past, when fat hoarding was a means of survival A species of birds called petrels become obese as chicks due to the need to consume more calories than they burn

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20. Concept 41.2: An animal ’ s diet must supply carbon skeletons and essential nutrients An animal must obtain carbon skeletons from its food to build complex molecules Besides fuel and carbon skeletons, a diet must supply essential nutrients in preassembled form A malnourished animal is missing one or more essential nutrients in its diet

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Herbivores may suffer mineral deficiencies if they graze on plants in soil lacking key minerals

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23. Malnutrition is much more common than undernutrition in human populations

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential Amino Acids Animals require 20 amino acids and can synthesize about half from molecules in their diet The remaining amino acids, the essential amino acids, must be obtained from food in preassembled form A diet that provides insufficient essential amino acids causes malnutrition called protein deficiency

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26. Most plant proteins are incomplete in amino acid makeup Individuals who eat only plant proteins need to eat a variety to get all essential amino acids

27. LE 41-10 Methionine Valine Threonine Phenylalanine Leucine Isoleucine Tryptophan Lysine Essential amino acids for adults Beans and other legumes Corn (maize) and other grains

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some animals have adaptations that help them through periods when their bodies demand extraordinary amounts of protein

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30. Essential Fatty Acids Animals can synthesize most of the fatty acids they need The essential fatty acids are certain unsaturated fatty acids Deficiencies in fatty acids are rare

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Vitamins Vitamins are organic molecules required in the diet in small amounts 13 vitamins essential to humans have been identified Vitamins are grouped into two categories: fat- soluble and water-soluble

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34. Minerals Minerals are simple inorganic nutrients, usually required in small amounts

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36. Concept 41.3: The main stages of food processing are ingestion, digestion, absorption, and elimination Ingestion is the act of eating Digestion is the process of breaking food down into molecules small enough to absorb Absorption is uptake of nutrients by body cells Elimination is the passage of undigested material out of the digestive compartment

37. LE 41-12 Pieces of food Chemical digestion (enzymatic hydrolysis) Food Nutrient molecules enter body cells Small molecules Undigested material ELIMINATION ABSORPTION DIGESTION INGESTION Mechanical digestion

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Digestive Compartments Most animals process food in specialized compartments These compartments reduce risk of self-digestion

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Intracellular Digestion In intracellular digestion, food particles are engulfed by endocytosis and digested within food vacuoles

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Extracellular Digestion Extracellular digestion is the breakdown of food particles outside of cells It occurs in compartments that are continuous with the outside of the animal’s body

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animals with simple body plans have a gastrovascular cavity that functions in both digestion and distribution of nutrients Video: Hydra Eating Daphnia Video: Hydra Eating Daphnia

42. LE 41-13 Gastrovascular cavity Mouth Food Tentacles Epidermis Gastrodermis Mesoglea Gland cells Flagella Nutritive muscular cells Food vacuoles Mesoglea

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings More complex animals have a digestive tube with two openings, a mouth and an anus This digestive tube is called a complete digestive tract or an alimentary canal It can have specialized regions that carry out digestion and absorption in a stepwise fashion

44. LE 41-14a Gizzard Intestine Anus Crop Esophagus Pharynx Mouth Earthworm Typhlosole Lumen of intestine

45. LE 41-14b Foregut Midgut Hindgut Rectum Anus Esophagus Mouth Crop Gastric ceca Grasshopper

46. LE 41-14c Anus Esophagus Mouth Crop Bird Stomach Gizzard Intestine

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 41.4: Each organ of the mammalian digestive system has specialized food-processing functions The mammalian digestive system consists of an alimentary canal and accessory glands that secrete digestive juices through ducts Mammalian accessory glands are the salivary glands, the pancreas, the liver, and the gallbladder Food is pushed along by peristalsis, rhythmic contractions of muscles in the wall of the canal

48. LE 41-15a Esophagus Pharynx Oral cavity Stomach Pyloric sphincter Cardiac orifice Liver Tongue Parotid gland Sublingual gland Submandibular gland Salivary glands Ascending portion of large intestine Gall- bladder Pancreas Ileum of small intestine Rectum Anus Appendix Cecum Large intestine Small intestine Duodenum of small intestine

49. LE 41-15b Esophagus Stomach Liver Salivary glands Gall- bladder Pancreas Rectum Anus Large intestines Small intestines Mouth A schematic diagram of the human digestive system

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Oral Cavity, Pharynx, and Esophagus In the oral cavity, food is lubricated and digestion begins Teeth chew food into smaller particles that are exposed to salivary amylase, initiating breakdown of glucose polymers

51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The region we call our throat is the pharynx, a junction that opens to both the esophagus and the windpipe (trachea) The esophagus conducts food from the pharynx down to the stomach by peristalsis

52. LE 41-16_3 Epiglottis up Bolus of food Esophageal sphincter contracted Esophagus To stomach To lungs Trachea Tongue Pharynx Glottis Larynx Esophageal sphincter relaxed Epiglottis down Glottis up and closed Epiglottis up Esophageal sphincter contracted Relaxed muscles Glottis down and open Relaxed muscles Contracted muscles Stomach

53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Stomach The stomach stores food and secretes gastric juice, which converts a meal to acid chyme Gastric juice is made up of hydrochloric acid and the enzyme pepsin Pepsin is secreted as inactive pepsinogen; pepsin is activated when mixed with hydrochloric acid in the stomach Mucus protects the stomach lining from gastric juice

54. LE 41-17 Esophagus Cardiac orifice Pyloric sphincter Small intestine Folds of epithelial tissue Stomach Epithelium Pepsin (active enzyme) Pepsinogen HCl Pepsinogen and HCl are secreted into the lumen of the stomach. HCl converts pepsinogen to pepsin. Pepsin then activates more pepsinogen, starting a chain reaction. Pepsin begins the chemical digestion of proteins. Parietal cellChief cell Chief cells Mucus cells Parietal cells Interior surface of stomach Gastric gland 5 µm

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gastric ulcers, lesions in the lining, are caused mainly by the bacterium Helicobacter pylori

56. LE 41-18 Bacteria Mucus layer of stomach 1 µm

57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Small Intestine The small intestine is the longest section of the alimentary canal It is the major organ of digestion and absorption

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Enzymatic Action in the Small Intestine The first portion of the small intestine is the duodenum, where acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and the small intestine itself

59. LE 41-19 Stomach Pancreas Liver Gall- bladder Duodenum of small intestine Intestinal juice Bile Acid chyme Pancreatic juice

60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The pancreas produces proteases, protein- digesting enzymes that are activated after entering the duodenum

61. LE 41-20 Pancreas Lumen of duodenum Membrane-bound enteropeptidase Inactive trypsinogen Other inactive proteases Active proteases Trypsin

62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The liver produces bile, which aids in digestion and absorption of fats The epithelial lining of the duodenum, called the brush border, produces several digestive enzymes Enzymatic digestion is completed as peristalsis moves the chyme and digestive juices along the small intestine

63. LE 41-21 Oral cavity, pharynx, esophagus Stomach Lumen of small intes- tine Smaller polysac- charides, maltose Polysaccharides Disaccharides Carbohydrate digestion Salivary amylase Polysaccharides Pancreatic amylases Maltose and other disaccharides Epithelium of small intestine (brush border) Disaccharidases Monosaccharides Protein digestionNucleic acid digestion Proteins Fat digestion Fat globules DNA, RNA Fat droplets Nucleotides Bile salts Pancreatic lipase Pancreatic nucleases Nucleotidases Glycerol, fatty acids, glycerides Nitrogenous bases, sugars, phosphates Nucleosides Nucleosidases and phosphatases Dipeptidases, carboxy- peptidase, and aminopeptidase Amino acids Small peptides Pancreatic carboxypeptidase Pancreatic trypsin and chymotrypsin Smaller polypeptides Polypeptides Small polypeptides Pepsin

64. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hormones help coordinate the secretion of digestive juices into the alimentary canal

65. LE 41-22 Pancreas Stomach Entero- gastrone Gall- bladder Liver Duodenum Secretin CCK Stimulation Inhibition Gastrin Key

66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Absorption of Nutrients The small intestine has a huge surface area, due to villi and microvilli that are exposed to the intestinal lumen The enormous microvillar surface greatly increases the rate of nutrient absorption

67. LE 41-23 Key Nutrient absorption Microvilli (brush border) Epithelial cells Lacteal Lymph vessel Villi Large circular folds Epithelial cells Blood capillaries Vein carrying blood to hepatic portal vessel Muscle layers Villi Intestinal wall

68. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Each villus contains a network of blood vessels and a small lymphatic vessel called a lacteal

69. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Amino acids and sugars pass through the epithelium of the small intestine and enter the bloodstream After glycerol and fatty acids are absorbed by epithelial cells, they are recombined into fats within these cells These fats are mixed with cholesterol and coated with protein, forming molecules called chylomicrons, which are transported into lacteals

70. LE 41-24 Fat droplets coated with bile salts Fat globule Bile salts Micelles made up of fatty acids, monoglycerides, and bile salts Epithelium of small intestine Epithelium of lacteal Lacteal

71. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Large Intestine The large intestine, or colon, is connected to the small intestine Its major function is to recover water that has entered the alimentary canal Wastes of the digestive tract, the feces, become more solid as they move through the colon Feces pass through the rectum and exit via the anus

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73. The colon houses strains of the bacterium Escherichia coli, some of which produce vitamins

74. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 41.5: Evolutionary adaptations of vertebrate digestive systems are often associated with diet Digestive systems of vertebrates are variations on a common plan However, there are intriguing adaptations, often related to diet

75. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some Dental Adaptations Dentition, an animal’s assortment of teeth, is one example of structural variation reflecting diet Mammals have specialized dentition that best enables them to ingest their usual diet

76. LE 41-26 Incisors Carnivore Canines Premolars Molars Herbivore Omnivore

77. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stomach and Intestinal Adaptations Herbivores generally have longer alimentary canals than carnivores, reflecting the longer time needed to digest vegetation

78. LE 41-27 Small intestine Stomach Cecum Colon (large intestine) Carnivore Herbivore Small intestine

79. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbiotic Adaptations Many herbivores have fermentation chambers, where symbiotic microorganisms digest cellulose The most elaborate adaptations for an herbivorous diet have evolved in the animals called ruminants

80. LE 41-28 IntestineRumen Reticulum Omasum Esophagus Abomasum