25-1 copyright 2010 mcgraw-hill australia pty ltd powerpoint slides to accompany biology: an...
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25-1Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Chapter 25: Animal and human nutrition
25-2Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
What nutrients do animals need?• Animals are heterotrophs
– cannot synthesise organic compounds from inorganic molecules
– rely on other organisms for nutrients
• Nutrients– organic compounds
carbohydrates, lipids
– chemical compounds amino acids, fatty acids vitamins, minerals
25-3Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Plants as food• Plant tissues
– mostly carbohydrate monosaccharides, disaccharides, starches cellulose, pectin
– some lipid (mostly unsaturated fatty acids)– little protein– minerals depend on soil
• Composition may change seasonally and with locality
25-4Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Animals as food• Animal tissues
– mostly protein– some lipid (saturated fatty acids, unsaturated fatty acids
in fish)– little carbohydrate
• Carnivores can produce glucose from proteins and other materials– gluconeogenesis
25-5Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 25.2: Composition of some foods
25-6Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
How much food do animals require?• Nutrient requirements depend on
– age– reproductive state– metabolic rate
• Metabolic rate varies with– level of activity– body mass– environmental conditions
25-7Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Basal metabolic rate• Endotherms
– metabolic rate in inactive animal in thermoneutral environment (within thermal comfort zone)
• Ectotherms– metabolic rate in inactive animal is temperature-
dependent
25-8Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Metabolic rate and body mass• Relationship between metabolic rate and body
mass– mass-specific metabolic rate
metabolic rate per unit body mass
– small animals require more energy per unit body mass than do large animals
• Relationship between body mass and quality of food– small animals eat higher-quality (more energy-rich) food
than do large animals
25-9Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 25.4: Nutritional quality and body mass
25-10Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
The digestive process• Food must be broken down into molecules small
enough to enter cells– digestion
• Process of digestion– physical
mechanical activity of teeth or gizzard
– enzymatic chemical action of enzymes
25-11Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Enzymatic digestion• Digestive enzymes usually have low specificity
– act on types of substrates (e.g. proteins) rather than on specific bonds
• Sequential breakdown– complex molecules are broken down into successively
simpler ones as they pass through the gut
25-12Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Control of digestive secretion in humans• Nervous control
– saliva: is under nervous control and contains salivary enzymes
• Hormonal control– gastrin: stimulates release of hydrochloric acid and
pepsinogen in stomach– secretin: stimulates release of bile from gall bladder– cholecystokinin: stimulates release of trypsinogen from
pancreas
Question 1:
If acid and enzymes in the stomach can digest meat and other foods, why is the stomach lining itself not digested?
a) Digestion of foods does not take place until food exits the stomach
b) Very little hydrochloric acid is produced in the stomach
c) The stomach secretes a layer of mucus forming a layer that coats the stomach lining
d) The pH level in the stomach is nearly neutral so there is no need to worry about the lining
25-13Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Box 25.1: Stomach ulcers and the Nobel Prize
• Australians Robin Warren and Barry Marshall won the Nobel Prize for discovering role of Heliobacter pylori in gastric ulcers
• Marshall infected himself deliberately
25-14Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
25-15Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Intracellular and extracellular digestion• Intracellular digestion
– food taken into the cell for digestion is exposed to enzymes while enclosed in a vacuole
• Extracellular digestion – food digested externally is exposed to mechanical and
chemical (enzyme) digestion outside the cells– breakdown products are taken into the cells after
digestion
25-16Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Digestive systems• Single-celled organisms and sponge cells engulf
food that they digest in intracellular vacuoles– phagocytosis
• Multicelled organisms have specialised organs and tissue for digestion– vary in complexity from blind-ending digestive cavities to
digestive systems with associated secretory organs
Fig. 25.8: Amoeba feeding
25-17Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
25-18Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Simple digestive cavities• A simple sac-like gut with specialised digestive
tissue is found in cnidarians (corals, sea anemones and allies)– waste expelled through mouth– water dilutes action of enzymes
• A similar gut is found in platyhelminthes (flatworms)– convoluted gut increases surface area for absorption– decreases distance travelled by diffusing nutrients
25-19Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 25.10: Gastrovascular cavity of Hydra
25-20Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Two openings: one-way movement of food• Food passes through gut in one direction
– waste is eliminated at terminal anus
• Regional specialisation of gut, allowing sequential secretion of enzymes
• Food moved along gut by – body movements – ingestion of more food– peristalsis in animals with muscular gut wall
Question 2:
What are the advantages of a one-way digestive tract?
a) It is less complex and more efficient, so it uses less energy
b) Animals with a one-way digestive system can typically eat more varied food than others
c) One-way gut systems are not very susceptible to poisons
d) All of the above
25-21Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
25-22Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Chitinous mouthparts: arthropods• Chitinous paired mouthparts in arthropods
– specialisation in diet
• In insects, modification of the basic pattern of mouthparts allows a range of diets, including liquid feeders– nectar– plant sap– fruit– blood– tears
25-23Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Jaws and teeth: vertebrates• Teeth covered with hard enamel• Fish
– teeth and jaws specialised for different diets needle-like teeth in predators flattened teeth in herbivores
– specialist feeders molluscivores polyp predators
• Teeth-bearing bones in upper and lower jaws can be moved– kinesis
25-24Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Jaws and teeth: vertebrates (cont.)• Reptiles
– undifferentiated peg-like teeth– no lateral movement in jaw for chewing– snakes can disarticulate lower jaw and move elements
independently
• Birds– consume easily-digestible food– teeth lost to reduce weight for flight– mechanical processing by muscular gizzard
Fig. 25.15: Bird digestive system
25-25Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
25-26Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Mammals• Teeth differentiated
– specialised for different functions
• Incisors grasp and hold• Canines stab and grip• Premolars shear• Molars grind
25-27Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Mammals (cont.)• Teeth differentiated
– specialised for different diets
• Herbivores: crushing and grinding teeth for tough plant fibres
• Carnivores: tearing and shearing teeth for animal flesh
• Insectivores: crushing and puncturing teeth for invertebrate exoskeletons
Fig. 25.16: Tasmanian devil
25-28Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 25.17: Eastern grey kangaroo
25-29Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
25-30Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Filter feeding• Animals extract small organisms or other particles
by filtering large volumes of water• Examples
– invertebrates sponges, bivalves, tunicates
– vertebrates whale sharks, fish, flamingos, baleen whales
Fig. 25.19a: Baleen whale
25-31Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
25-32Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Digesting cellulose• Structural materials in cell walls are difficult to
digest– structural carbohydrates inaccessible to most herbivores
• Cellulose broken down by enzyme cellulase– few animals produce cellulase– many have colonies of symbiotic bacteria and protists in
gut these produce cellulase microbial fermentation
25-33Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Microbial fermentation• Symbiotic bacteria and protists
– hydrolyse cellulose into glucose– use glucose– produce short-chain fatty acids as wastes
acetic acid propionic acid butyric acid
– also ferment proteins
• Host – uses fatty acids as energy source– digests microbes for essential amino acids
25-34Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Site of microbial fermentation• Foregut
– food held in anterior part of stomach– foregut fermenters
example: kangaroos
– ruminant foregut fermenters example: sheep
• Hindgut– food held in caecum and colon
example: koala
25-35Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 25.20a: Foregut fermentation
25-36Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 25.20b: Foregut fermentation
25-37Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Ruminants• Ruminants regurgitate contents of anterior
stomach (rumen, reticulum) and chew it again– cannot pass through to omasum unless particles are
small enough
• Food retained for prolonged period– extends time for fermentation
• High fibre/low quality foods must be chewed for longer than low fibre/high quality food– limits amount of food that can pass through gut per unit of
time
25-38Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 25.23b: Hindgut fermentation
25-39Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Hindgut fermentation• Sugars and proteins in cell contents hydrolysed by
herbivore’s digestive enzymes• Undigested cell walls pass through to hindgut
– site of microbial fermentation
• Microbes not digested (as they are in foregut fermenters)– pass out in faeces, so source of amino acids is lost
• Microbial protein recovered by caecotrophy (coprophagy)
Summary• Animals are heterotrophic and must obtain organic
compounds from other organisms• All animals need energy, nitrogen-containing
compounds, fats, vitamins, minerals and water• Plant tissues are rich in carbohydrates, but
generally poor sources of protein. The reverse is true for animal tissues
• Digestion is necessary for food to be absorbed• Animal evolution has resulted in a diverse range of
digestive systems specialised to utilise very different foods
25-40Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University