1 41.4: evolutionary adaptations Of vertebrate digestive systems

2 Evolutionary AdaptationsDigestive Systems of Vertebrates Associated with the Animal’s Diet Form Fits Function

3 Dental Adaptations Dentition: an animal’s assortment of teethAn example of structural variation reflecting diet Mammals: successful because of adaptation of teeth for processing different food types

4 Incisors Molars Canines Premolars (a) Carnivore (b) HerbivoreFig Incisors Molars Canines Premolars (a) Carnivore (b) Herbivore Figure Dentition and diet (c) Omnivore

5 Dental Adaptations Nonmammalian Vertebrates Snakes: an exceptionLess specialized dentition Snakes: an exception Hollow fangs- venom Jaws that unhinge

6 Stomach and Intestinal AdaptationsCarnivorous Vertebrates: Expandable stomachs Herbivores and Omnivores: Longer alimentary canals (digestive tracts) for vegetation More time for digestions More surface area for absorption of nutrients

7 Colon (large intestine)Fig Small intestine Stomach Small intestine Cecum Figure The alimentary canals of a carnivore (coyote) and herbivore (koala) Colon (large intestine) Carnivore Herbivore

8 Mutualistic AdaptationsMutualistic Symbiosis: interaction that is beneficial for both species Herbivores: have mutualistic relationship with microorganisms Cannot digest cellulose from plant cell walls Microorganisms contain enzymes that can digest cellulose

9 Mutualistic AdaptationsRuminants: deer, sheep, and cattle Contain most elaborate adaptations for diet

10 Rumen Reticulum Intestine Esophagus Abomasum Omasum 1 2 4 3 Fig. 41-20Figure Ruminant digestion 4 Abomasum 3 Omasum

11 41.5: Homeostatic mechanisms Contribute to an animal’sEnergy balance

12 Homeostatic MechanismsAnimals balance energy from food with energy used for metabolism, activities, and storage

13 Energy Sources and StoresATP generations based on oxidation of carbohydrates, proteins, and fats Excess calories stored as glycogen in liver and muscle cells Glycogen oxidized when fewer calories are taken in than used

14 Energy Sources and StoresGlycogen synthesis and breakdown: regulated by hormones Insulin and glucagon

15 Stimulus: Blood glucose level rises after eating.Fig Stimulus: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood Stimulus: Blood glucose level drops below set point. Figure Homeostatic regulation of cellular fuel

16 Energy Sources and StoresAdipose (fat) cells: secondary site of energy storage Body Needs Energy: Goes to… Liver glycogen Muscle glycogen Muscle fat

17 Overnourishment and ObesityOvernourishment: consumption of more calories than the body needs for normal metabolism Causes obesity: excessive accumulation of fat Obesity contributes to: Type 2 diabetes Cancer of colon or breast Cardiovascular disease– heart attacks and strokes

18 Fig 100 µm Figure Fat cells from the abdomen of a human

19 Overnourishment and ObesityHomeostatic mechanisms: regulate body weight Hormones regulate appetite by affecting a “satiety center” in the brain

20 Ghrelin Insulin Leptin PYY Fig. 41-23Figure A few of the appetite-regulating hormones Insulin Leptin PYY

21 Overnourishment and ObesityLeptin: hormone made by fat cells Sends signal to brain to reduce appetite Mice used to study leptin and obesity

22 Fig EXPERIMENT Obese mouse with mutant ob gene (left) next to wild-type mouse. RESULTS Figure What are the roles of the ob and db genes in appetite regulation?

23 Obese mouse with mutant ob gene (left) next to wild- type mouse.Fig a EXPERIMENT Figure What are the roles of the ob and db genes in appetite regulation? Obese mouse with mutant ob gene (left) next to wild- type mouse.

24 Obesity and Evolution Fat hoarding: advantage in evolutionary pastEx: hunter-gatherers on African Savannah Relationship between fat storage and evolution can be complex Ex: Seabirds called petrels

25 Fig Figure A plump petrel

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