Digestion: Obtaining & Processing Food Herbivores = plant-eaters Herbivores = plant-eaters Carnivores = meat-eaters Carnivores = meat-eaters Omnivores = both plants and other animals Omnivores = both plants and other animals

Digestion: Obtaining Food Solid foods Filtering from water substrate feeders fluid feeders

Digestion: 4 Stages

Digestion Mechanical Breakdown: Mechanical Breakdown: Physically breaking food apart (teeth, tongue, stomach, etc) Physically breaking food apart (teeth, tongue, stomach, etc) Chemical Breakdown: Chemical Breakdown: enzymes and secretions to break down chemically enzymes and secretions to break down chemically

Digestion: Chemical Breakdown

Digestion: Protozoans Intracellular digestion with oral groove or phagocytosis Intracellular digestion with oral groove or phagocytosis

Digestion Gastrovascular cavity vs specialized digestive tract Gastrovascular cavity vs specialized digestive tract Gastrovascular cavity: one opening Gastrovascular cavity: one opening cnidarian & flatworms cnidarian & flatworms

Digestion: Alimentary Canal Most have alimentary canal Most have alimentary canal Tube running from mouth to anus Tube running from mouth to anus divided into specialized regions that process food sequentially divided into specialized regions that process food sequentially Crop: stores food Crop: stores food Gizzard: grinds food (especially if no jaws or teeth) Gizzard: grinds food (especially if no jaws or teeth)

Digestion: Human Alimentary Canal vs Accessory Organs Alimentary Canal vs Accessory Organs

Digestion: Human Alimentary Canal Alimentary Canal mouth, esophagus, stomach, small intestines, large intestines, rectum, anus Accessory Organs Accessory Organs salivary glands, liver, gall bladder, pancreas

Digestion: Mouth Mechanical Digestion Mechanical Digestion Teeth, tongue Teeth, tongue Chemical Digestion Chemical Digestion Saliva moistens it Saliva moistens it Salivary enzymes amylase begin breakdown of starch Salivary enzymes amylase begin breakdown of starch Tongue pushes the chewed food into the pharynx Tongue pushes the chewed food into the pharynx

Digestion: Esophagus Peristalsis: muscle contractions pushing down bolus (food) Peristalsis: muscle contractions pushing down bolus (food)

Digestion: Stomach

Stomach mixes food with gastric juice from gastric glands Stomach mixes food with gastric juice from gastric glands Gastric glands – make HCl, pepsinogen, mucous Gastric glands – make HCl, pepsinogen, mucous HCl activates pepsinogen (inactive enzyme) to form pepsin (enzyme to breakdown protein) HCl activates pepsinogen (inactive enzyme) to form pepsin (enzyme to breakdown protein) HCl also kills germs HCl also kills germs Mucous – lines & protects stomach walls Mucous – lines & protects stomach walls Chyme (partially digested food) enters duodenum (beginning of small intestines via pyloric sphincter Chyme (partially digested food) enters duodenum (beginning of small intestines via pyloric sphincter

Digestion: Small Intestines

Digestion: Small Intestine / Pancreas / Liver / Gall Bladder Most of chemical digestion and absorption take place in small intestines Most of chemical digestion and absorption take place in small intestines Pancreas Pancreas Makes bicarbonate (HCO 3 - ), base that neutralizes stomach acid Makes bicarbonate (HCO 3 - ), base that neutralizes stomach acid Pancreatic enzymes digest polysaccharides, proteins, nucleic acids, and fats Pancreatic enzymes digest polysaccharides, proteins, nucleic acids, and fats Bile (made in liver, stored in gall bladder) emulsifies (mechanical breakdown) fat droplets for attack by pancreatic lipase Bile (made in liver, stored in gall bladder) emulsifies (mechanical breakdown) fat droplets for attack by pancreatic lipase Trypsin breaks down protein in base environment Trypsin breaks down protein in base environment

Digestion: Small Intestine Absorption by villi Absorption by villi

Digestion: Large Intestines Absorption of water Absorption of water E Coli live in LI, make Vitamin K E Coli live in LI, make Vitamin K Undigested material = feces Undigested material = feces

Digestion: Evolutionary Adaptations Plant harder to digest than meat because of cellulose Plant harder to digest than meat because of cellulose Herbivores have longer digestive tract Herbivores have longer digestive tract

Digestion Cows have 4 stomach chambers to break down cellulose Cows have 4 stomach chambers to break down cellulose