ANIMAL NUTRITION CHAPTER 41

Figure 41.0 Animals eating: foal, bear, and stork

Figure 41.5 Storing protein for growth by increasing muscle mass. Proteins are used for molting (growing new feathers).

Figure 41.2 A ravenous rodent. The obese rat has a defective gene which normally produces an appetite-regulating protein.

DIETARY CATEGORIES Herbivores – eat mainly autotrophs Carnivores – eat mainly animals Omnivores – eat animals, plants,and/or algae

FEEDING MECHANISMS Suspension-feeders – sift small food particles from water –clams, oysters, baleen whales

Figure 41.6 Suspension-feeding: a baleen whale

Substrate-feeders – live in or on their food source, eating their way through the food –Leaf miners (tunnel through leaves) –Earthworms (more specifically deposit feeders)

Figure 41.7 Substrate-feeding: a leaf miner

Fluid-feeders – sucking nutrients from living hosts –Mosquitoes, leeches, aphids

Figure 41.8 Fluid-feeding: a mosquito

Bulk-feeders – eat relatively large pieces of food –Most animals

Figure 41.9 Bulk-feeding: a python

FOUR MAIN STAGES OF FOOD PROCESSING Ingestion Digestion –Enzymatic hydrolysis Absorption Elimination

INTRACELLULAR DIGESTION Food vacuoles fuse with lysosomes that have hydrolytic enzymes to digest food –Sponges (entirely intracellular digestion) –Paramecium – oral groove leads to making food vacuole

Figure Intracellular digestion in Paramecium

Figure Extracellular digestion in a gastrovascular cavity

EXTRACELLULAR DIGESTION Breakdown food outside of cells in gastrovascular cavities Some have single opening (Incomplete digestive tract) –Cnidarians and flatworms

Two openings (Complete digestive tract or alimentary canal) – tube with mouth and anus –Most animals –Mouth, pharynx, esophagus, (crop, gizzard), stomach, intestine, and anus

Figure Alimentary canals

MAMMALIAN DIGESTIVE SYSTEM Peristalsis – contraction of smooth muscles in wall of canal Sphincters – ring-like valves Salivary glands, pancreas, liver, gall bladder

Figure The human digestive system

HUMAN DIGESTIVE SYSTEM Oral Cavity –Mucin (glycoprotein) – protects soft lining –Salivary amylase – hydrolyzes starch –Bolus- food ball that is swallowed

The Pharynx –Epiglottis (cartilaginous flap) –Esophageal sphincter contracts, epiglottis up –Esophageal sphincter relaxed, epiglottis covers trachea, food moves into esophagus

Figure From mouth to stomach: the swallowing reflex and esophageal peristalsis

Stomach –Secretes gastric juice (high amounts of HCl) –pH is approximately 2 –Pepsin (in gastric juice) hydrolyzes proteins Chief cells secrete inactive pepsinogen Parietal cells secrete HCl that converts pepsinogen into pepsin

–Stomach lining replaced every 3 days –Ulcers normally caused by acid- tolerant bacteria (Helicobacter pylori) –Churning produces acid chyme –Closed at esophagus end by cardiac orifice –Closed to small intestine at pyloric sphincter

Figure Secretion of gastric juice

Small Intestine –Longest section of canal –Where most absorption occurs –First 25 cm = duodenum –In duodenum digestive juices from pancreas, liver, gall bladder, and gland cells enter

Pancreas –Produces hydrolytic enzymes and bicarbonate (to reduce acidity) Liver –Production of bile (with bile salts) that aids in digestion of fats Gall bladder –Stores bile

Figure The duodenum

Small Intestine (in duodenum) Carbohydrate digestion –Pancreatic amylases hydrolyze polysaccharides Protein Digestion –Trypsin and Chymotrypsin break bonds between certain amino acids

–Carboxypeptidase splits off one amino acid at a time at carboxyl end –Aminopeptidase chops off one amino acid at amino end –Dipeptidase, enteropeptidase also involved

Fat digestion –Fat insoluble in water –Bile salts emulsify fat droplets to keep them from coalescing –Lipase hydrolyzes fat Nucleic acid digestion –Nucleases

Figure Enzymatic digestion in the human digestive system

Figure Activation of protein-digesting enzymes in the small intestine

–Absorption of nutrients (mostly in jejunum and ileum) –Increased surface area by villi and microvilli –Each villi contains capillaries and lacteal (small lymphatic vessel); each only one cell thick –Nutrients move via diffusion and active transport –Fats move into lacteal –All other nutrients empty into capillaries and eventually move into hepatic vessel to liver

Figure The structure of the small intestine

Large Intestine (colon) –Connected to small intestine at T- shaped junction One arm is cecum that leads to appendix in humans Other arm is the colon –Reabsorbs water –Leftover waste is feces –Feces stored in rectum and released through anus –E. coli in colon

Figure 41.x1 Large intestine

EVOLUTIONARY ADAPTIONS Teeth vary according to what the animal eats –Fangs, incisors, canines, “grinders” Herbivores and omnivores longer alimentary canals than carnivores due to cellulose digestion

Figure Dentition and diet

Figure The digestive tracts of a carnivore (coyote) and a herbivore (koala) compared

Special chambers to digest cellulose with help of p rokaryotes and some protists –Ruminants (examples: cattle and sheep)

Figure Ruminant digestion

Figure 41.x2 Termite and Trichonympha