41.4: evolutionary adaptations Of vertebrate digestive systems

Evolutionary Adaptations Digestive Systems of Vertebrates Associated with the Animal’s Diet Form Fits Function

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

Incisors Molars Canines Premolars (a) Carnivore (b) Herbivore Fig. 41-18 Incisors Molars Canines Premolars (a) Carnivore (b) Herbivore Figure 41.18 Dentition and diet (c) Omnivore

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

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

Colon (large intestine) Fig. 41-19 Small intestine Stomach Small intestine Cecum Figure 41.19 The alimentary canals of a carnivore (coyote) and herbivore (koala) Colon (large intestine) Carnivore Herbivore

Mutualistic Adaptations Mutualistic 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

Mutualistic Adaptations Ruminants: deer, sheep, and cattle Contain most elaborate adaptations for diet

Rumen Reticulum Intestine Esophagus Abomasum Omasum 1 2 4 3 Fig. 41-20 Figure 41.20 Ruminant digestion 4 Abomasum 3 Omasum

41.5: Homeostatic mechanisms Contribute to an animal’s Energy balance

Homeostatic Mechanisms Animals balance energy from food with energy used for metabolism, activities, and storage

Energy Sources and Stores ATP 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

Energy Sources and Stores Glycogen synthesis and breakdown: regulated by hormones Insulin and glucagon

Stimulus: Blood glucose level rises after eating. Fig. 41-21 Stimulus: Blood glucose level rises after eating. Homeostasis: 90 mg glucose/ 100 mL blood Stimulus: Blood glucose level drops below set point. Figure 41.21 Homeostatic regulation of cellular fuel

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

Overnourishment and Obesity Overnourishment: 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

Fig. 41-22 100 µm Figure 41.22 Fat cells from the abdomen of a human

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

Ghrelin Insulin Leptin PYY Fig. 41-23 Figure 41.23 A few of the appetite-regulating hormones Insulin Leptin PYY

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

Fig. 41-24 EXPERIMENT Obese mouse with mutant ob gene (left) next to wild-type mouse. RESULTS Figure 41.24 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. Fig. 41-24a EXPERIMENT Figure 41.24 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.

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

Fig. 41-25 Figure 41.25 A plump petrel