Blood sugar levels regulated by pancreatic hormones insulin and glucagon

Obtaining essential nutrients Storing protein for growth

Can be obtained by eating a diet of corn and beans Body cannot make these

Vitamins: non-energy foods, organic molecules required in small amounts, regulate body functions

Minerals: non-energy foods, inorganic molecules required in small amounts, regulate body functions

FOOD TYPES & FEEDING MECHANISMS Suspension feeders Substrate feeders Fluid feeders Bulk feeders

Intracellular Digestion Sponges Heterotrophic protists FOOD PROCESSING Ingestion Digestion Absorption Enzymatic hydrolysis

Extracellular Digestion Occurs within compartments that are continuous with the outside of the animal’s body Specialized cells secrete enzymes Gastrovascular cavity with single opening – Cnidarians Platyhelminthes? Alimentary canal - Nematodes, Annelids, Mollusks, Arthropods, Echinoderms, Chordates

Complete Digestive System: mouth, pharynx, crop, gizzard, intestine, anus

PHYSICAL DIGESTION Mastication – chewing Deglutition – swallowing Peristalsis – wave like muscle contractions through alimentary canal Segmentation – mixing food & enzymes Emulsification – bile from liver breaking large lipids into small lipids

CHEMICAL DIGESTION Carried out by hydrolases Proteins → amino acids Carbohydrates → disaccharides Disaccharides → monosaccharides Lipids → glycerol + 3 fatty acids Nucleic acids → nucleotides

Alimentary canal? Accessory organs?

Oral cavity: begins physical digestion (chewing) and chemical digestion of carbohydrates (salivary amylase) Note epiglottis & peristalsis

STOMACH Begins breakdown of proteins Gastrin Pepsinogen → pepsin HCl Mucus Chyme Pyloric sphincter Cardiac sphincter NOTE

Makes bile Stores bile Secretes sodium bicarbonate and enzymes Accessory organs: liver, gall bladder, pancreas Hormones: Secretin Cholecystokinin

Enzymatic Digestion - Human

Activation of protein digesting enzymes in small intestine Break down large polypeptides into shorter chains Enteropeptidase – triggers activation of enzymes

ABSORPTION OF NUTRIENTS Capillaries: monosacch., aa., minerals, vitamins, water, some glycerol Lacteals: fatty acids & most glycerol *

INTESTINES Small Intestine: Length (6 m); surface area (300 m 2 ) Duodenum (digestion) Jejunum & Ileum (absorption) Hepatic portal system Large Intestine (colon): Ascending, Transverse, Descending, Sigmoid Cecum, Appendix, Rectum, Feces Absorption of water Bacteria

Dentition & Diet Canines – killing & ripping Incisors – biting Molars - grinding

Longer intestine for processing fibrous diet Cecum – fermentation chamber housing symbiotic bacteria

Ruminant digestion – most elaborate adaptation of all herbivores; aided by symbiotic bacteria and protists