Quiz Why are deposit feeders important in marine environment o Convert a nonusable form of food into a form that can be used by the rest of the food web aerate the sediment via bioturbation stabilize the sediments Quiz Main function of digestive system o Break down food mechanically break down food chemically absorption of nutrients expel undigested materials from the body Quiz Main benefit of a complete digestive system o Regional specialization of the digestive process Digestion Absorption and Energy Budgets Digestion process of splitting up ingested food molecules into smaller chemical components that an animal is capable of distributing to the tissues of its body Extracellular digestion digestion in an extracellular body cavity such as the lumen of the stomach or intestines o Vertebrates arthropods Intracellular digestion food particles are taken into specialized cells prior to digestion and digestion occurs w in the cell o Sponges cnidarians flatworms 3 types of stomachs o Batch reactor least efficient food ingested first then digested then egested one batch of food at a time cnidarians sharks Cnidarians polyps and medusa have gastrovascular cavity used for feeding gastro and circulation vascular only one opening o Complete digestive system tube within a tube unidirectional passage of food Advantages specialized feeding structures teeth regional specialization food breakdown nutrient absorption storage elimination of indigestible 2 body plans among those with complete digestive system pseudocoelomate eu coelomate o Continuous flow stirred tank reactor food ingested continually newly ingested food mixes with previously ingested food efficiency varies strongly by configuration of stomach and with feeding speed speed that food moves through stomach crabs food is sometimes not digested completely b c they re consistently eating food low in efficiency o Plug flow reactor food continually ingested unidirectional flow of food through gut no mixing higher concentration of digestive enzymes towards the front so digestion fastest in anterior portion very high digestion efficiency sperm whales humans very high in efficiency Variation in digestive systems depends on evolutionary adaptations structure varies strongly with diet function generally the same Vertebrates vs arthropods vs molluscs o Vertebrates headgut mouth tongue pharynx foregut esophagus stomach crop gizzard midgut small intestine hindgut large intestines Peristalsis muscle contractions of intestines moves food o Arthropods foregut esophagus cardiac stomach pyloric stomach midgut Contraction of muscles attached to stomach moves food no muscles in stomach o Molluscs cilliary food movement intracellular digestion Cilliary tracts bring food particles into each digestive diverticulum help move things along Digestion happens inside the cells Intracellular digestion o Food brought into cell by phagocytosis or pinocytosis Produces food vacuole endosome o Lysosome produced by endomembrane system Contains digestive enzymes o Two merge and digestion occurs o Indigestible material expelled by exocytosis Extracellular Digestion o Digestive enzymes released o Food particles broken down o Food particles engulfed and digested Quiz efficiency of digestion Digestive system tasks o Mechanical Breakdown Depends on type of organism whale sharks swallow food whole polar bear tears off chunks of food crabs shred food completely o Secretion of digestive enzymes Digestive function of the stomach Mixes food Digestive enzymes are secreted at all different steps of this process Diet specific enzyme activity Physiological adaptations for specific foods Consequences for trying to eat the wrong food not enough digestions and nutrition Process of breaking down large molecules into smaller molecules that can be absorbed by cells occurs by hydrolysis using the digestive enzymes o Absorption Occurs in different locations for different animals many in the intestine Occurs at molecular level across membranes so organisms maximize membrane SA Villi and microvilli on intestine brush border cells break down bacteria nutrient absorption max SA for absorption o Questions Quiz Questions o Final step of process takes place in the cell o Given this location what is the benefit of increasing the SA with villi Greater uptake by cells and enhanced endocytosis same thing o Other than increasing SA what else can an organism alter in order to increase absorption of digested food The time the food is in the stomach increasing volume doesn t increase efficiency Digestion takes time the longer food is in the gut the more gets digested increases efficiency Quiz increasing temperature increases digestion rate of sharks Environmental Moment trash in the ocean o Leatherback turtles classified as critically endangered worldwide o Wanted to see if plastic really is responsible for turtle mortality o Partial or complete obstruction of digestive tract o Plastic covers microvilli that absorb nutrients from food o Many marine mammals eat trash Elimination of Waste Ambergris o Protective substance that protects whale intestine from sharp objects like squid beaks o Passes out intestine or vomited o Washes onto beach o Collected and sold to make perfumes Sperm Whales fight global warming with carbon neutral feces o Have very highly concentrated amounts of Fe o Huge phytoplankton blooms where sperm whales feed more nutrients low chlorophyll o Phytoplankton sink to bottom and take carbon with them Digestion facilitation with body heat o Stomach warms to a max of 10 15 C above water temperature over a period of 12 2 hours o Heat comes from digestive process itself metabolic heat and from muscle contraction o Heat loss reduced by overlying gas bladder and by thick fatty muscle of the body wall as well as by heat exchanges in the circulation o Speeds digestion allowing animals to feed frequently when food is abundant o Also increases swimming speeds o Cold blooded fish sharks acting warm blooded o Counter current exchange mechanism shunt warm blood to cold blood back into digestive system so the core of the fish is warmer increases efficiency speed of digestion Energy Budgets Food consumed and assimilated provides energy that s necessary for growth reproduction Laws of thermodynamics Rorqual whale feeding how can blue whales get so big and fat o Conversion efficiency between trophic levels is 10 o Eat low down on food chain don t lose a bunch of energy by feeding buoyancy of water reduces