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Adaptations for Nutrition
BY2 Biology
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Nutrition The process organisms use to get
energy to maintain life functions and matter to build and maintain their structure (from nutrients)
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Types of Nutrition Autotrophs - use simple inorganic materials to manufacture complex organic compounds (also called producers) Ex: photosynthesis - plants use carbon dioxide, water and light energy to make sugars Ex: chemosynthesis - bacteria around deep sea vents-use carbon dioxide and sulphur compounds (as energy) to create organic compounds Heterotrophs - consume complex organic food material (also called consumers)
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What do heterotrophs need to live?
They make energy using: Food (organic compounds such as carbohydrates, protein..) Oxygen They build bodies using: food for raw materials amino acids, sugars, fats, nucleotides ATP energy for synthesis O2 food ATP This includes animals, fungi, some protoctists and some bacteria
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Overview of food processing
Ingest taking in food Digest mechanical digestion breaking up food into smaller pieces chemical digestion breaking down food into soluble molecules small enough to be absorbed into cells uses enzymes (hydrolysis) Absorb Digested food moves across cell membrane diffusion active transport Assimilate use compounds in the body Egestion undigested extracellular material passes out of digestive system (ex: cellulose in humans) intracellular digestion extracellular digestion
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Types of Heterotrophic Nutrition
Holozoic feeders: Take food into their bodies and break is down during digestion Have specialised organs in a digestive system (gut) After digestion, the nutrients are absorbed into the body Saprophytes (saprobionts): Fungi and some bacteria Feed on dead or decaying matter No specialised digestive system Secrete enzymes onto the food source outside their body for extra- cellular digestion and absorb the soluble products by diffusion (enzymes include protease, amylase, lipase, cellulase) Some are decomposers and help to recycle nutrients in the ecosystem
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Mutualism (symbiosis):
Parasites: Highly specialised organisms Feed on other living organisms (a host) Some live inside the host (endoparasites) other live on the outside (ectoparasites) The host is always harmed Ex: tapeworm, potato blight (fungus), plasmodium (causes malaria) Mutualism (symbiosis): 2 different species live in a helpful relationship Ex: cows use bacteria in their stomach to help digest cellulose and the bacteria gain nutrients from the broken plant material for growth and energy
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How do animals get their food?
filter (suspension) feeding substrate feeding fluid feeding bulk feeding
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Food types/feeding mechanisms
Heterotrophs Opportunistic Herbivore: eat autotrophs Carnivore: eat other animals Omnivore: both Feeding Adaptations Suspension feeders - sift food from water (baleen whale) Substrate feeders -live in or on their food (leaf miner) (earthworm: deposit-feeder) Fluid-feeders -suck fluids from a host (mosquito) Bulk-feeders: eat large pieces of food (most animals)
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Digestive systems
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Simple More complex In simple organisms: In more advanced organisms:
feeding on only one type of food the gut is undifferentiated In more advanced organisms: Often have a varied diet, the gut is divided into various parts along its length and each part is specialised to carry out particular functions Organisms with a varied diet require more than one type of enzyme to carry out the digestion of the different food substrates
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Human Digestive System
Overview animation
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Mouth (buccal cavity) mechanical digestion by teeth to break up food (mastication/chewing) moistens food by mixing with saliva to lubricate it for swallowing chemical digestion - amylase digests starch saliva Contains: water (to soften food) mucus (to protect the lining of the digestive system) amylase (breaks starch to maltose) mineral ions to keep mouth pH alkaline (act as a buffer) Anti-bacterial chemicals to kill germs
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Swallowing (& not choking)
Epiglottis problem: breathe & swallow through same orifice flap of cartilage closes trachea (windpipe) when swallowing food travels down esophagus Esophagus move food along to stomach by peristalsis
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stomach acid (secreted from oxyntic cells in wall) kills germs stores food for up to 4 hrs (sphincter at each end) mixes food by moving wall with contractions (churning) gastric juice secreted from glands (peptic cells) in stomach wall digest proteins secretes mucus (from goblet cells) to protect stomach lining from acid and enzymes Gastric juice Contains: Acid (pH =2) kills germs and provide optimum pH for pepsin Peptidase enzymes (ex: pepsin) to hydrolyse protein to polypetides cardiac sphincter pyloric sphincter
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Human Digestion Peristalsis: rhythmic waves of contraction by smooth muscle Sphincters: ring-like valves that regulate passage of material Accessory glands: salivary glands; pancreas; liver; gall bladder (secrete digestive juices)
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Tissue Layers The gut wall consists of four tissue layers surrounding a central cavity (lumen)- Serosa – tough connective tissue to protect the wall and reduce friction with other organs when it moves) Muscle Layer – longitudinal muscle and circular muscle running in different directions Cause peristalsis when circular muscles contract and longitudinal relax)
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Submucosa – connective tissue with blood vessels and lymph vessels to carry away absorbed food
Has nerves to coordinate peristalsis Mucosa- secretes music to lubricate and protect the mucosa Secretes digestive juices in some areas Absorbs digested food in others
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Glands There are a number of different glands which produce digestive secretions: Some are found in the wall of the gut with the secretions passing directly into the gut cavity Mucus secreting glands (submucosa) Gastric glands (mucosa) Glands at base of villi (mucosa) Others are found outside the gut with the secretions passing along ducts into the gut cavity Salivary Pancreas Liver
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The human alimentary canal
Consists of: buccal cavity Tongue Salivary glands Oesophagus Stomach Duodenum Ileum Colon Rectum Anus associated organs; liver and pancreas
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Small intestine Function Structure
major organ of digestion & absorption chemical digestion digestive enzymes absorption through lining over 6 meters! small intestine has huge surface area = 300m2 (~size of tennis court) Structure 3 sections duodenum = most digestion jejunum = absorption of nutrients & water ileum = absorption of nutrients & water About every 20 seconds, the stomach contents are mixed by the churning action of smooth muscles. As a result of mixing and enzyme action, what begins in the stomach as a recently swallowed meal becomes a nutrient-rich broth known as acid chyme. At the opening from the stomach to the small intestine is the pyloric sphincter, which helps regulate the passage of chyme into the intestine. A squirt at a time, it takes about 2 to 6 hours after a meal for the stomach to empty.
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Duodenum 1st section of small intestine Liver gall bladder pancreas
acid food from stomach mixes with digestive juices from accessory glands: Glands in wall also secrete: alkaline juice (optimum for enzymes) and mucus (lubrication and protection) Liver gall bladder pancreas
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Duodenum Enzymes on the tip of the villi complete digestion: Maltase
Endopepsidase Exopepsidase
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Liver produces bile salts Digestive System Functions
stored in gallbladder until needed Help neutralise stomach acid breaks up fats by lowering the surface tension of lipids act like detergents to breakup fats into tiny droplets (emulsifier) Circulatory System Connection bile contains colors from old red blood cells collected in liver = iron in RBC rusts & makes feces brown
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Pancreas Secretes pancreatic juice via pancreatic duct
Digestive enzymes Endopeptidases (protein peptides) Pancreatic amylase (starch maltose) Lipase (lipids fatty acids + glycerol) Buffers reduces acidity alkaline solution rich in bicarbonate (HCO3-) buffers acidity of material from stomach
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Absorption by Small Intestines
Adaptations for absorption Very long Highly folded for higher surface area Folds contain finger-like villi Villi contain microvilli
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Absorption by Small Intestines
Absorption through villi & microvilli Glucose and amino acids are absorbed by diffusion and active transport into capillaries and then travel via the hepatic portal vein to the liver. There are lots of mitochondria present in these cells Fatty acids and glycerol are passed into the lacteal, then through the then through the lymphatic system to the blood stream opening at the thoracic duct.
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A longitudinal section through a villus - you can see the 'brush border' created by the microvilli, the arrow points to mucus in a goblet cell
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mouth break up food moisten food digest starch kill germs stomach kills germs break up food digest proteins store food liver produces bile - stored in gall bladder break up fats small intestines breakdown all foods - proteins - starch - fats - nucleic acids absorb nutrients pancreas produces enzymes to digest proteins & starch
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Large intestine 4 parts: Caecum Appendix Colon Rectum Function
re-absorb water and mineral salts in colon use ~9 liters of water every day in digestive juices > 90% of water reabsorbed not enough water absorbed back to body diarrhea too much water absorbed back to body constipation
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Flora of the large intestine
Living in the large intestine is a rich flora of harmless, helpful bacteria Escherichia coli (E. coli) bacteria produce vitamins vitamin K, folic acid & other B vitamins generate gases by-product of bacterial metabolism methane, hydrogen sulfide Folic acid: coenzyme needed for DNA & RNA synthesis and proper neural tube growth, may have role in cancer prevention Biotin: coenzyme needed for Krebs cycle, fatty acid synthesis & gluconeogenesis
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Rectum Salts cells that have sloughed off masses of bacteria
Last section of large intestine eliminate faeces undigested materials mainly cellulose from plants (roughage or fiber) Salts extracellular waste cells that have sloughed off masses of bacteria Cellulose fibre is required to provide bulk and stimulate peristalsis. The study of the rabbit is fascinating, and from periods of quiet observation we learn some of the peculiarities of its life and habits. One of the most interesting of these is coprophagy. The word comes from the Greek kopros (dung) and phago (eating). This dung eating is not quite so revolting as it sounds at first, for the rabbit makes a special form of pellet which it takes directly from its anus. Coprophagy plays an important part in the digestive/nutritional process. This practice involves ingestion of special soft fecal pellets which are excreted in the early morning hours. This is a significant practice in that the bacterial synthesis of certain B vitamins in the cecum are excreted at this time and if rabbits are prevented from this practice they will die from vitamin B deficiency within a rather short period of time. The special soft pellets are produced at night or during periods of rest and are often called "nocturnal pellets" to distinguish them from the fecal pellets excreted at other times. The process has a distinct analogy with the chewing of the cud by ruminants. Like the cow, rabbits are herbivorous and their diet contains a high proportion of crude fiber. The cellulose of the fiber has to be broken down before complete digestion and absorption can take place. The rabbit has a comparatively large caecum and colon to facilitate this. In order to obtain the maximum nutriment from its food the rabbit has developed the habit of coprophagy, passing certain of its intestinal contents through the system twice. In addition to the improved nutrition, it is possible that the soft pellets fulfill a need to give greater bulk to the stomach contents. The rabbit's stomach and intestines are geared to bulk supplies and under some conditions the diet may lack bulk. The stomach has a comparatively poor muscular action and relies to a great extent on the pressure of successive meals to push the mass of food along the digestive tract. The composition of the two types of pellets is interesting, the soft pellets having much more protein and less crude fiber. The process is controlled by adrenal glands.
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mouth break up food moisten food digest starch kill germs stomach kills germs break up food digest proteins store food liver produces bile - stored in gall bladder break up fats small intestines breakdown food - proteins - starch - fats absorb nutrients pancreas produces enzymes to digest proteins & carbs large intestines absorb water
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Summary of enzymes Called hydrolases as they catalyse the hydrolysis of molecules Enzyme group Enzyme Location Substrate Products Other Carbohydrases Amylase Mouth Duodenum Pancreas Starch Maltose Maltose is further broken down Maltase Glucose Glucose used as an energy source in respiration Excess glucose is converted to fat Proteases Peptidase (ex: pepsin) Stomach Polypeptides then amino acids Amino acids Endopeptidases hydrolyse peptide bonds within the protein Exopeptidases hydrolyse peptide bonds near the end of proteins Amino acids are absorbed for protein synthesis Excess amino acids cannot be stored so is deaminated, whereby the removed amino groups are converted to urea and the deaminated remainder is converted to carbohydrate and stored lipase Lipase Fats Fatty acids & glycerol Lipids are used for membranes and hormones, and the excess is stored as fat.
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Review digestive system in humans Overview animation
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Evolutionary adaptations to different diets
Adaptations of herbivore vs. carnivore specialization in teeth length of digestive system number & size of stomachs
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Evolutionary adaptations to different diets
Animals have different diets and methods of feeding. Ex: Retiles and amphibians-swallow food whole immediately so no need for teeth for chewing Mammals cut and chew food before swallowing and so have adapted different types of teeth
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Dentition Mechanical digestion (cutting and chewing food) increases surface area for enzyme action and make swallowing easier Mammals have evolved different types of teeth with each type being specialised for a different function
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Teeth There are differences between the teeth of carnivores and herbivores reflecting their differing diets
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Carnivore teeth Adapted for:
Catching/piercing skin & killing – large, curved pointed canines Crushing bones – premolars and molars Tearing meat – canines Scrape meat off the bone - incisors Carnassials – specialized molars (cheek teeth) that slide past each other like scissors to cut and crush Jaw Powerful with strong muscles Does not move side to side (to prevent dislocation) Greater vertical movement to open wide to capture prey
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Herbivore Teeth Adapted for: Jaw: Must grind plant material
(due to cellulose) before swallowing Adapted for: Cutting plants - Incisors on the lower jaw only and a horny pad on the upper jaw to cut against or help to pull grass (no canines). Grinding - wide molars and premolars (cheek teeth) that interlock/fit into each other. These teeth get worn down but can regrow throughout life Jaw: Diastema – gap between front teeth and premolars at side where the tongue can push the cut grass to the grinding surface at the back and push food to the back over again and again Moves in a circular grinding action on the horizontal plane
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Omnivore Teeth Example: 32 Human teeth (adult) both kinds of teeth
8 incisors (chisel shape) for biting and cutting 4 canines (pointed) for tearing 8 premolars 12 molars (flat) for grinding
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Length of digestive system
Carnivores No need to digest cellulose or starch so less chemical digestion in mouth More acid in stomach (so can often eat rancid food) short digestive system protein easier to digest than cellulose Herbivores & omnivores long digestive system more time to digest cellulose symbiotic bacteria in gut
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Symbiotic organisms How can cows digest cellulose efficiently?
symbiotic bacteria in stomachs help digest cellulose-rich meals rabbit vs. cow adaptation: eat feces vs. chew cud caprophagy ruminant Ruminants additional mechanical digestion by chewing food multiple times after mixing it with enzymes
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Ruminants (ex: cows and sheep)
Eat mainly grass, a large proportion of which consists of cellulose cell walls Have a 4 chambered stomach Process: Food chewed and mixed with saliva Then passed to the rumen (first stomach) in which mutualistic bacteria live and break down cellulose to glucose (since ruminants do not have the enzyme cellulase) Glucose is fermented to an organic acid and absorbed into the blood for energy. Waste gases include carbon dioxide and methane
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Ruminants plant material is passed up from the rumen and reticulum back into the mouth periodically until it is completely chewed up (known as chewing the cud). Material is then passed from the rumen and reticulum (no real function) into the omasum (next chamber) where water is absorbed Then it is passes to the abomason (last chamber) where hydrochloric acid and protease digest protein Then the material continues into the small intestine for absorption of products
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The Bacteria Mutualistic - both benefit – mammals gets food broken down further and bacteria gets food supply brought to it and shelter bacteria must be kept in an isolated area with optimum pH (not killed by pH in other parts of gut) More bacteria than in caecum, so more efficient at breaking down cellulose When bacteria die they get passed along the digestive system as a source or protein
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Rabbits Coprophagy is consumption of faeces by animals.
Rabbits do not have a complex ruminant digestive system. They must extract excess amount of nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets or partially digested food are excreted and consumed immediately Consuming this matter is important for adequate nutritional intake of vitamin B 12.
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