Ch 41 Animal Nutrition (digestion)

1. Ch 41 Animal Nutrition (digestion) Learning goals: 1 Draw and label a simple cladogram of the animal phyla using derived characteristics of digestive structures, and explain the physiological basis for these changes being necessary 2Compare and contrast: a) intracellular digestion in sponges versus paramecia, b) intracellular digestion of sponge and gastrovascular cavity digestion of cnidaria , & c) gastrovascularcavity digestion in flatworms to digestion in nematodes or annelids having a closed circulatory system.

2. 3 Explain how the feeding mechanism of an earthworm is fit for its ecological niche, and explain how the relative locations of the blood vessels and intestines of the earthworm facilitate delivery of nutrients/waste.4 Explain how negative feedback by the endocrine system is needed for glucose metabolism.5 Explain how hunger is controlled by 2 opposing hormones (endocrine system)6 Identify the source, names, substrates, and sites of action of enzymes used in the human digestive system. 7. Describe the theadaptive value of being cold blooded (ectothermic) versus warm blooded (endothermic)8 Explain how feeding strategies of insects, amphibia, reptiles, birds, & snails and octopi/squi are adapted for their ecological niches.

3. L G 1 Cladogram of animal phyla sorted by digestive strategy

4. LG 2a Describe the process of intracellular digestion for a paramecium, and contrast it with that of a sponge. Explain how the strategies are fit for the organisms’ ecological niches. In paramecia, endocytosis happens at the oral groove & waste exocytosis at the anal pore.

5. In sponges, extracellular digestion works the same, but 1 celled prey are first captured on the flagella of feeding cells called choanocytes or collar cells. Water from waves of shallow seas washes through 1 celled phyto or zooplankton as it passes through pores and out osculum.

6. Describe how hormones of the endocrine system regulate hunger. • Describe the 4 stages of digestion of each of these nutrients in a mammal:starch and other carbohydrateslipidsproteinsName the enzymes or acid/bases/buffers made instomach, intestinal walls, & pancreas, and describe the role of each.Explain the importance of pepsinogen and trypsinogen versus pepsin and trypsin secretion.

7. An example of negative feedback regulation (oppose the change from homeostasis) is regulation of blood sugar levels—insulin from beta cells of pancreas raises blood sugar levels (by stimulating break up of glycogen in liver to glucose) but glucagon secreted by alpha cells of pancreas lowers it (by stimulation of glycogen formation from blood sugar & storage in liver).

8. Steps in digestion of all animals with digestion that is not intracellular. Only animals with intracellular digestion: sponges, cnidaria, & flatwork (in cnid., fltw, gastrovascular cavity is location of flagellated feeding cells)

9. Intracellular digestion of cnidaria—foods captured in gastrovascular cavity; hydra & some tiny cnidarians use intracellular digestion, but others do utilized digestive enzymes in the gastrovascular cavity followed by diffusion of monomers.

10. Thicker invertebrate animals require digestive systems. Mouthcrop/gizzardintestine w digestive glands (break up, absorb) OR mouthcrop/gastric cecaglands/intestine OR mouthcrop/stomach/gizzard/glandsintestine.

11. The protostomes and deuterostomes have digestive systems that include a mouth & anus (all except flatworms who are acoelomates), but other structures vary with adaptation to the econiche. (remember crop, gizzard, gastric ceca versus stomach in insects)

12. The human digestive system contains various organs with different functions.

14. Stomach walls both mechanically digest food & make protein digesting enzymes. HCl is secreted under control of involuntary nerves, then it cleaves pepsinogenpepsin. It’s mucous coat protects it from HCL & pepsin. Example: Keep the inactive protein around, then activate on demand!

15. Liver makes bile (detergent to emulsify fats) then gallbladder stores it; stomach’s role is mechanical digestion and partial protein digestion; small intestine role—complete digestion, neutralize chyme, mix with pancreatic digestive enzymes, absorb molecules into blood stream.

16. Small intestine (duodenum) makes inactive trypsinogen which is cleaved to trypsin when acid chyme enters.

17. Enzymes to remember

18. Adaptation of lower small intestine (ileum) to maximize diffusion rates:--Folding into microvilli composed of sheets of brush border epithelia + ciliated brush border epithelia increase surface area, --lymph (tissue fluid) & blood capillaries directly underneath the thin epithelial layer --2 perpendicular smooth muscle layers controlled by central nervous system move liquids (peristalsis)

19. Large veins (hepatic portal veins) connect the blood vessels of the small intestine to the liver Nitrogenous waste is generated in the liver where amino acid and nucleotide digestion is completed. The digestion of these molecules is not complete when blood first arrives in the intestine.

20. Bile is a detergent made in the liver, then stored in gall bladder, then secreted via ducts into small intestine where it solubilizes fats to allow them to be substrates of pancreatic lipase. Fatty acid monomers are absorbed into the lacteal (lymph vessels) inside the microvilli.

21. The colon of the large intestines resorbs water. E coli and other enteric bacteria are mutualistic symbionts of the intestine. They help break down fibrous foods, in particular, and they secrete vitamin K, necessary for clotting.

22. The kidney (not part of the digestive system) removes nitrogenous waste produced by digestion of nucleotides & proteins. The kidneys are supplied through large renal veins and arteries that merge into the inferior aorta and inferior vena cava. It is essential that all of the blood be filtered through the kidney after amine & amino groups are removed. NH3 is toxic!

23. The cecum is vestigial in humans, a blind pocket off the colon. In ruminant herbivores, it’s a site of mutualistic symbiosis: It provides nutrients, water, & shelter micro-organisms whose sectreted cellulase enzyme allows herbivore (who don’t make cellulase) to extract nutrients tied surrounded by thick cellulose cell walls.