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Comparative Digestive System Notes
Biology I Academic
Bacteria Examples: E. coli, Staphylococcus aureus
Digestive Process: autotrophs or heterotrophs Special Info: Photoautotrophs – convert light into energy; Chemoautotrophs – convert chemicals like ammonia, nitrites or sulfur into energy
Protists Examples: Paramecium, Euglena, slime mold
Digestive Process: Animal-like can: 1. absorb food through their cell membranes; 2. capture & digest food or other cells; 3. use cilia to sweep food into gullet; 4. be parasitic; Plant-like undergo photosynthesis; Fungus-like are decomposers Special Structures: gullet – pockets that trap food & force them into food vacuoles where it is stored. Chloroplasts – convert light energy into sugar
Gullet Anal pore Food vacuoles Cilia
Fungi Examples: mushrooms, yeast, mold
Digestive Process: Heterotrophic decomposers Special Info: Mycelium allows contact with a large surface area to extract nutrients from.
Plants Examples: grasses, trees, flowering plants
Digestive Process: autotrophs – photosynthesis Special Structures: Chloroplasts; stomata – pores for gas exchange; mesophyll – cells that absorb light
Porifera Examples: Sponges
Digestive Process: Filter feeders that sift microscopic food particles out of the water
Cnidarians Examples: Jellyfish, sea anemones, corals & hydra
Digestive Process: Paralyzes prey with stinging cells & draws them in to the gastrovascular cavity Special Structures: Cnidocytes – stinging cells containing nematocysts. Nematocysts are shot into the prey when triggered. Gastrovascular cavity – the digestive chamber with only 1 opening
Cnidocytes & Nematocysts
Flatworms Examples: tapeworms, flukes, planaria, turbellarians
Digestive Process: Carnivorous or parasitic feeding off a host. They have a single opening for both food & waste to pass through. Special Structures: Pharynx – a muscular tube that is extended out of the mouth to pump food into the digestive cavity
Roundworms Examples: Hookworms, Ascaris worms, Trichinella, Filarial worms Digestive Process: Predators (free-living) or parasitic (most); first organisms with a 2-opening digestive system Special Structures: anus – posterior end of the digestive tract where waste is excreted
Annelids (segemented worms)
Examples: earthworms, leeches, ragworms Digestive Process: filter feeders, predators, or external parasites; have a pharynx Special Structures: Earthworms pharynx pumps food into an esophagus, then into a crop (stores food), then into a gizzard (grinds food) and finally into the intestine (absorbs food).
Mollusks Examples: clams, oysters, snails, squid & octopi
Digestive Process: clams, oysters, scallops – filter feeders; snails are carnivores; octopi & squid are predators Special Structures: snails -radula to drill through shells of prey; filter feeders – food enters the siphon
Nut weevil mouthparts adapted to bore into & eat nuts
Arthropods Examples: insects, crustaceans, spiders Digestive Process: herbivores, carnivores, omnivores, parasitic; Special Info: have highly adapted mouthparts for their food source; spiders must liquefy their food before consuming (no jaws) Nut weevil mouthparts adapted to bore into & eat nuts
Echinoderms Examples: sea stars, sea urchins, sand dollars, sea cucumbers Digestive Process: herbivores & carnivores; Sea urchins eat algae off rocks Sea stars & lilies use tube feet Sea stars throw their stomach out of their mouths, pour out enzymes & digest mollusks in their own shell Special Structures: tube feet – used to pry open shells of mollusks or to capture plankton
Fish Examples: salmon, sharks, lampreys
Digestive Process: all modes of feeding; Digestive pathway: mouth esophagus stomach pyloric ceca anus; liver & pancreas secrete digestive enzymes Special Structures: pyloric ceca – secretes digestive enzymes & absorbs nutrients from digested food
Fish Digestion Pyloric ceca
Amphibians Examples: frogs, toads, salamanders, caecilians
Digestive Process: tadpoles filter feeders or herbivores; adults carnivores Special Structures: cloaca – structure at the end of the intestine that wastes, urine, eggs or sperm leave from
Reptiles Examples: lizards, snakes, crocodiles, alligators, turtles, tortoises Digestive Process: herbivores, carnivores; some swallow prey whole Gaboon vipers stretch their jaws wide, unhinging them & swallow their prey whole.
Birds Examples: pelicans, owls, parrots, toucans, crows, herons, ostriches Digestive Process: Digestion pathway = (mouth crop gizzard stomach small intestine cloaca) Special Structures/Info: Crop & gizzard; small birds have to eat more than larger birds b/c they lose heat faster
Mammals Examples: marsupials, platypus, elephants, rabbits, lions, whales, primates, anteaters, pigs Digestive Process: all modes of feeding Special Structures/Info: specialized teeth dependent on food type; cows have chambered stomachs called rumen that allow them to break down plants.
I. Nutrition A. Major Nutrients 1. Water 2. Carbohydrates 3. Fats
4. Proteins 5. Vitamins 6. Minerals
B. Food Guide Pyramid
II. Digestion System A. Function – to chemically and mechanically break down foods, causing the absorption of nutrients into the blood stream.
Gallbladder (behind liver)
Mouth Salivary glands Stomach Pancreas (behind stomach) Large intestine Small intestine Rectum Gallbladder (behind liver) Liver Esophagus Pharynx
B. Digestion Pathway 1. Mouth – chemically (saliva) & mechanically breaks down food Esophagus – food tube that takes food to the stomach a. Peristalsis – Smooth muscle contractions move the food down
Stomach – mechanical and chemical digestion
a. Pepsin breaks down proteins during chemical digestion into smaller amino acids b. A mixture of food & stomach fluids called chyme is produced during mechanical digestion 4. Small intestine – chemical digestion and the absorption of nutrients a. Contain villi – tiny finger-like projections that line the inside of the small intestine; increase the surface area for the absorption of nutrients
Villi in the Intestines
The surface of your small intestine is covered with microvilli such as these (magnification: 100x).
5. Large intestine a. removes water from indigestible waste and sends waste out of the rectum b. colonies of bacteria produce vitamin K in the large intestine
Other Digestive Organs (not part of food pathway)
1. Liver a. produces bile that helps to break down fats b. bile is stored in the gall bladder 2. Pancreas a. produces enzymes that are help break down food b. produces a substance that neutralizes stomach acid c. Produces hormones to regulate blood sugar
Accessories to Digestion
A – Esophagus F – Pancreas
B – Gall bladder G – Small intestines C – Liver H – Large intestines D – Stomach E – Duodenum
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