1. Animal Nutrition

2. Nutritional Requirements
Nutritional diet fulfills 3 needs:
1Fuel – energy for work.
2Raw materials – for biosynthesis.
3Essential nutrients – body can’t make.
Flow of energy in/out – budget.

4. ATP comes from oxidation of organic molecules.
Take in more calories than needed – rest for biosynthesis.
Liver stores excess as glycogen; above and beyond stores, stores as fat.

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6. Regulation of blood glucose: glucose levels rise – pancreas secretes insulin – stimulates liver to store excess – decreases levels.
Glucose drops – pancreas secretes glucagon – breakdown of glycogen – increases levels.

8. Fewer calories than needed – fuel taken out of storage (liver 1st, muscles 2nd)
Most people have enough stores to last weeks.
Undernourishment – uses muscles for energy, eventually brain.
Even if survives, permanent damage occurs.

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10. Overnourishment – excessive food intake – results in obesity.
Advantage during hunting/gathering days.
Human body has set weight – sets limits on weight loss/gain.

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12. Leptin (hormone) – produced by adipose cells – decreases hunger (when levels high).
Decrease causes increase in appetite.

14. Obesity beneficial in some species (travel long distances)
Animal’s diet must supply materials for biosynthesis.
Also supply essential nutrients (i.e. vitamin C)

16. Missing nutrients – malnourished.
More common than undernourishment.
20 amino acids needed to make proteins – eight are essential (needed from diet).
Protein deficiency most common malnourishment – causes mental retardation in children.

18. Animal proteins – complete (have all essential amino acids)
Plant proteins – incomplete.
Combination in plants fulfill all essentials.
Can’t be stored – need to be eaten daily.

20. Animals adapt to needs – penguins use muscle proteins for energy for molting.
Essential fatty acids needed as well.
Vitamins – organic molecules needed in small quantities.
13 essential vitamins.

24. Minerals – inorganic nutrients needed in small amounts.
Excess of sodium (salt) dangerous – high blood pressure; excess iron – liver damage.

26. Food Types
3 categories of eating habits – 1herbivores (plant eaters), 2carnivores (meat eaters), 3omnivores (both)
Most animals opportunistic – will eat outside category if needed.
4 ways to ingest food.

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28. 1Suspenion-feeders – sift small particles from water (baleen whales)
2Deposit-feeders – eat through sediment; extract decaying organic material (earthworms)
3Substrate-feeders – live on food source (maggots)

31. 4Fluid-feeders – suck fluids from host (mosquitoes, leeches)
Most animals bulk-feeders – eat large pieces of food.
Use fangs, teeth, claws, etc. to eat food.

34. Overview of food processing
1Ingestion - food taken into system. (Eating)
Polymers broken down into monomers so body can digest them.
2Digestion - breaking food down into molecules small enough for body to absorb.

36. Digestion reverses process that cell uses to link together monomers to form macromolecules.
Mechanical digestion - physical breaking down of food; chemical digestion - act of enzymes on broken down food.

38. 3Absorption - animal’s cells take up small molecules (i. e
3Absorption - animal’s cells take up small molecules (i.e. amino acids, simple sugars) from digestive compartment.
4Elimination - undigested material passes out of digestive compartment.

40. To avoid digesting own self, most digestion compartmentalized.
In cell - food vacuoles - hydrolytic enzymes break down food without digesting cell’s own cytoplasm (intracellular digestion).

42. Protists - take in food by phagocytosis or pinocytosis.
Food digested in food vacuole, then fuses with lysosomes to break food down further.
Vacuole fuses with anal pore that eliminates it from body.

44. Extracellular digestion - food broken down outside cell.
Cnidaria have digestive sacs with single openings (gastrovascular cavities).
Food taken in, eliminated through same opening.

45. Fig
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46. Organisms have complete digestive tracts (alimentary canals) with mouth, digestive tube, anus - specialized to carry out digestion.
Food ingested through mouth, pharynx passes through esophagus to crop, gizzard, or stomach, depending on species.

48. Crop (or stomach) - food storage.
Gizzard - breaks down food.
Allows organisms to ingest additional food before earlier meals completely digested.

49. Fig
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50. Mammalian Digestive System
Consists of alimentary canal, various accessory glands that secrete digestive juices into canal through ducts.
Peristalsis, rhythmic waves of contraction by smooth muscles in walls of canal, push food along.

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52. Sphincters, muscular ring-like valves, regulate passage of material between specialized chambers of canal.
Accessory glands - salivary glands, pancreas, liver, gallbladder.

53. Fig
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54. Physical, chemical digestion of food begins in mouth.
Presence of food in oral cavity triggers nervous reflex - causes salivary glands to deliver saliva through ducts to oral cavity.
Salivation may occur in anticipation -learned associations between eating, time of day, cooking odors, etc.

56. Saliva contains mucin - helps food slide down esophagus easier.
Chemical digestion of carbohydrates main source of chemical energy, begins in oral cavity - done by salivary amylase.
Food made into ball - bolus.

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58. Pharynx (throat) - junction that opens to esophagus and trachea (windpipe).
Swallow - top of windpipe moves up - opening, glottis, blocked by cartilaginous flap, (epiglottis) - helps to prevent us from choking.

60. Not swallowing - esophageal sphincter muscles contracted - epiglottis up, glottis open, allowing airflow to lungs.
When food bolus reaches pharynx, larynx moves upward and epiglottis tips over glottis, closing off trachea.

62. Esophageal sphincter relaxes, bolus enters esophagus.
Larynx moves downward, trachea opened, peristalsis moves bolus down esophagus to stomach.

63. Fig
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64. Esophagus conducts food from pharynx down to stomach by peristalsis.
Stomach located in upper abdominal cavity, below diaphragm.
Stomach secretes digestive fluid (gastric juice), mixes secretion with food by churning action of smooth muscles in stomach wall.

66. Gastric juice secreted by epithelium lining numerous deep pits in stomach wall.
Contains hydrochloric acid (acidic enough to dissolve iron nails) and pepsin, enzyme that begins hydrolysis of proteins.

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68. Pepsin secreted in inactive form, pepsinogen, by specialized chief cells in gastric pits.
Parietal cells, also in pits, secrete hydrochloric acid - converts pepsinogen to active pepsin only when both reach lumen of stomach, minimizing self-digestion.

70. Stomach’s 2nd line of defense against self-digestion is coating of mucus, secreted by epithelial cells, protects stomach lining.
Ulcers occur when stomach lining eaten through.

72. Stomach churns food, produces chyme.
Sometimes chyme backs up into esophagus (heartburn).
Pyloric sphincter (at opening of small intestine) prevents material from moving into small intestine too quickly.

74. Small intestine longest section of alimentary canal.
Most absorption takes place here.
Duodenum - chyme from stomach mixes with digestive juices from pancreas, liver, gall bladder, gland cells of intestinal wall.

76. Liver performs wide variety of important functions in body, including production of bile.
Bile stored in gall bladder until ready to use.
Bile used to breakdown fats.
Each enzyme has specific role in digestion.

78. Starch, glycogen continue to be broken down in small intestine.
Pancreatic amylase aids in process.
Digestion of proteins in small intestine completes process begun by pepsin.
Done by several enzymes.

80. Trypsin, chymotrypsin attack peptide bonds adjacent to specific amino acids, breaking larger polypeptides into shorter chains.
Dipeptidases, attached to intestinal lining, split smaller chains.
Carboxypeptidase, aminopeptidase split off 1 amino acid from carboxyl or amino end of peptide, respectively.

82. Nucleic acids digested in small intestines by an enzyme (nuclease).
All fat in meal reaches small intestine undigested.
Emulsification allows fat droplets to be coated by bile so they can pass through system.
Lipase - enzyme that breaks fats down.

84. Most digestion occurs in duodenum.
Other 2 sections of small intestine, jejunum and ileum, function mainly in absorption of nutrients and water.
Nutrients in lumen must pass lining of digestive tract.

86. Surface area of small increased by microvilli - appendages off of villi.
Help increase amount of absorption.

87. Fig
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88. Transport of nutrients across epithelial cells can be passive.
Active mechanisms of digestion, including peristalsis, enzyme secretion, active transport, may require animal to expend amount of energy = 3% - 30% of chemical energy contained in meal.

90. Hormones released by wall of stomach and duodenum ensure digestive secretions present only when needed.
Can be released when we see or smell food.

92. Certain substances in food stimulate stomach wall to release hormone gastrin into circulatory system.
As recirculates, gastrin stimulates further secretion of gastric juice.
If pH of stomach contents become too low, acid will inhibit release of gastrin.

94. Other hormones, (enterogastrones), are secreted by walls of duodenum.
Cholecystokinin (CCK), secreted in response to presence of amino acids or fatty acids, causes gallbladder to contract, release bile into small intestine; triggers release of pancreatic enzymes.

96. Large intestine (colon) connected to small intestine where sphincter controls movement of materials.
Small cecum (1st part of colon) of humans has appendix - makes minor contribution to body defense.

98. Major function of colon - to recover water that has entered alimentary canal as solvent to digestive juices.
Digestive wastes, feces, become more solid as move along colon by peristalsis.

100. In large intestine - rich flora of mostly harmless bacteria.
Feces contain masses of bacteria and undigested materials including cellulose.
Terminal portion of colon - rectum, feces stored until eliminated.

102. 2 sphincters, 1 involuntary, 1 voluntary, control movement of feces out of rectum.

104. Evolutionary Adaptations
Vertebrate digestive systems alike, have some differences based on diets.
Dentition (animal’s assortment of teeth) example of structural variation reflecting diet.
Nonmammalian vertebrates - less specialized dentition (exceptions)

106. Snakes - ability to swallow food whole.
Unhinge jaw to get entire organism in.
Large, expandable stomachs common in carnivores - may go for long time between meals; must eat as much as they can when they catch prey.

108. Length of vertebrate digestive system correlated with diet.
More plants, longer tract seems to be to allow more time for digestion and reabsorption.

110. Most energy in plants comes from cell walls.
Cellulose cannot be digested by many organisms.
Symbiotic microbes can digest it. Location of symbiotic microbes in herbivores’ digestive tracts varies depending on species.

112. Most elaborate adaptations for herbivorous diet have evolved in ruminants (deer, cattle, sheep).
When cow first chews and swallows mouthful of grass, boluses enter rumen and reticulum.

114. Symbiotic bacteria, protists digest cellulose-rich meal, secreting fatty acids. Cow regurgitates, rechews cud, which further breaks down cellulose fibers. Cow reswallows cud, water removed.
Cud, with many microorganisms digested by cow’s enzymes.