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
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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
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LE 41-2a Baleen
LE 41-2b Caterpillar Feces
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
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
LE µm
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
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LE 41-5 Leptin PYY Insulin Ghrelin
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Obesity and Evolution The problem of maintaining weight partly stems from our evolutionary past, when fat hoarding was a means of survival
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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 A malnourished animal is missing one or more essential nutrients in its diet
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 Essential amino acids, must be obtained from food in preassembled form Malnutrition called protein deficiency occurs when a diet doesn’t contain all needed amino acids
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Kwashiorkor Caused by a protein deficiency
LE Methionine Valine Threonine Phenylalanine Leucine Isoleucine Tryptophan Lysine Essential amino acids for adults Beans and other legumes Corn (maize) and other grains
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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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Minerals Minerals are simple inorganic nutrients, usually required in small amounts
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 41.3: The main stages of food processing are ingestion, digestion, absorption, and elimination Ingestion Digestion Absorption Elimination
LE Pieces of food Chemical digestion (enzymatic hydrolysis) Food Nutrient molecules enter body cells Small molecules Undigested material ELIMINATION ABSORPTION DIGESTION INGESTION Mechanical digestion
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 Gastrovascular cavity Mouth Food Tentacles Epidermis Gastrodermis Mesoglea Gland cells Flagella Nutritive muscular cells Food vacuoles Mesoglea
LE 41-14a Gizzard Intestine Anus Crop Esophagus Pharynx Mouth Earthworm Typhlosole Lumen of intestine
LE 41-14b Foregut Midgut Hindgut Rectum Anus Esophagus Mouth Crop Gastric ceca Grasshopper
LE 41-14c Anus Esophagus Mouth Crop Bird Stomach Gizzard Intestine
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
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
Esophagus Stomach Liver Salivary glands Gall- bladder Pancreas Rectum Anus Large intestines Small intestines Mouth A schematic diagram of the human digestive system
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
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
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pepsinogen Pepsin HCl
LE 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gastric ulcers, lesions in the lining, are caused mainly by the bacterium Helicobacter pylori Bacteria Mucus layer of stomach 1 µm