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The burden of food

Why animals need energy. Animals are organized or ordered systems.Energy is brought into the system to maintain that orderEnergy definition: The capacity to do mechanical work or more broadly the capacity to increase order.Animals are open ordered systems that rely on the input of energy to main

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The burden of food

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    1. The burden of food In reproducing Perry’s trek to the North Pole by dogsled, the explorers had to haul mostly food for them and their animals. They carried 1400 lbs (630KG). The food was rich in fatsand oils—meat was 50% meat and 50% lard. Why do animals need energy? Energy metabolism is the sum of processes the following processes used by animals: acquisition of energy, channeling energy and dissipating energy. In reproducing Perry’s trek to the North Pole by dogsled, the explorers had to haul mostly food for them and their animals. They carried 1400 lbs (630KG). The food was rich in fatsand oils—meat was 50% meat and 50% lard. Why do animals need energy? Energy metabolism is the sum of processes the following processes used by animals: acquisition of energy, channeling energy and dissipating energy.

    2. Why animals need energy Animals are organized or ordered systems. Energy is brought into the system to maintain that order Energy definition: The capacity to do mechanical work or more broadly the capacity to increase order. Animals are open ordered systems that rely on the input of energy to maintain that order.

    3. Figure 6.1 The second law of thermodynamics in action In an isolated system (difficult to achieve) that undergoes internal changes the direction of change is always towards greater disorder. Over time the directional motion is gradually transformed to the energy of random motion. Movement of the molecules against the copper transfers energy to the copper, but in a way that increases random motion. The energy transferred causes the heat of the system to rise. The only way to keep the water flowing is to put energy into the system. Loss of order in an animal leads to death of an organism. Animals require energy from outside to create and maintain their internal organization.In an isolated system (difficult to achieve) that undergoes internal changes the direction of change is always towards greater disorder. Over time the directional motion is gradually transformed to the energy of random motion. Movement of the molecules against the copper transfers energy to the copper, but in a way that increases random motion. The energy transferred causes the heat of the system to rise. The only way to keep the water flowing is to put energy into the system. Loss of order in an animal leads to death of an organism. Animals require energy from outside to create and maintain their internal organization.

    4. Fundamental of animal energetics: 4 energy forms Chemical energy —energy liberated by the rearrangement of atoms Electrical energy —produced by the separation of positive and negative charge. Mechanical energy —produced by organized motion of the molecules. Molecular kinetic energy (heat) —energy of random atomic-molecular motion.

    5. Physiological work increases order Chemical energy can be used to do all forms of physiological work (totipotent). Electrical and mechanical energy can be used for some physiological work. Animals cannot use heat to do any form of physiological work in themselves. Work produced by heat requires a temperature difference. High-grade energy can do physiological work, low-grade energy cannot do physiological work. The degradation of heat by animals is the transformation of high-grade energy to heat.High-grade energy can do physiological work, low-grade energy cannot do physiological work. The degradation of heat by animals is the transformation of high-grade energy to heat.

    6. Transformation of high-grade energy Efficiency of energy transmission is less than 1. 70% of energy released from glucose is incorporated into ATP bonds. 30% is lost in heat 35-30% of the energy released from ATP is used in muscular contraction. Efficiency of energy transfer =output of high grade energy/input of high grade energy. Contraction efficiency of muscle depends on what kind of work they are doing. In using ATP almost 70-75% of the energy is lost as heat.Efficiency of energy transfer =output of high grade energy/input of high grade energy. Contraction efficiency of muscle depends on what kind of work they are doing. In using ATP almost 70-75% of the energy is lost as heat.

    7. The flow of energy in animals Flow of energy starts as ingested chemical energy. Egested chemical bond energy is fecal chemical energy. Ingested energy that is assimilated into the cells is absorbed chemical energy and this energy is available to perform physiological work. Ingested energy-egested energy=absorbed chemical energy An animal uses the energy to carry out three major tasks: Biosynthesis Maintenance Generation of external workAn animal uses the energy to carry out three major tasks: Biosynthesis Maintenance Generation of external work

    8. The 3 major physiological functions Biosynthesis Produce chemicals with chemical-energy content, i.e. ATP. Produce new cells and tissues. Produce organic compounds that are exported from the body during an animal’s life. New cells and tissues store energy for use during periods of starvation or for ingestion by other organisms after death. Organic compounds that are exported include milk, gametes, sloughed skin, hair, shed exoskeletons.New cells and tissues store energy for use during periods of starvation or for ingestion by other organisms after death. Organic compounds that are exported include milk, gametes, sloughed skin, hair, shed exoskeletons.

    9. The 3 major physiological functions Maintenance functions maintain the integrity of the body and this energy is entirely degraded to heat. Circulation, respiration, nervous coordination, gut motility, tissue repair. Mechanical work in the body is internal work

    10. The 3 major physiological functions Generation of external work is the application of forces to objects or forces outside the body. Energy is transmitted to the environment and is sometimes converted into potential energy. Figure 3.3 Energy driving upward locomotion is converted into heat and potential energy of position Potential energy is converted into mechanical energy as bicyclist descends and then to heat. Riding on flat terrain does not lead to storage of energy and the mechanical energy is degraded to heat in overcoming resistances to motion.Figure 3.3 Energy driving upward locomotion is converted into heat and potential energy of position Potential energy is converted into mechanical energy as bicyclist descends and then to heat. Riding on flat terrain does not lead to storage of energy and the mechanical energy is degraded to heat in overcoming resistances to motion.

    11. Figure 6.2 The uses of energy by an animal anphys-fig-05-02-0.jpg The flow of energy is one way. Heat is not used to form chemical bond energy or any other high form energy. Energy is not recycled in organisms Thus animals have to take in food. The biosphere needs a continual input of high-grade photon energy from the sun.anphys-fig-05-02-0.jpgThe flow of energy is one way. Heat is not used to form chemical bond energy or any other high form energy. Energy is not recycled in organisms Thus animals have to take in food. The biosphere needs a continual input of high-grade photon energy from the sun.

    12. Metabolic rate The metabolic rate is the rate of energy consumption or the rate at which an animal converts chemical energy into heat and external work. Metabolic rate affects how much food needs to be ingested. Metabolic rate can be measured to quantitatively determine total activity of all physiological mechanisms. Metabolic rate measures the drain produced by an animal on its ecosystem The rate of degradation of chemical energy or organic compounds.

    13. Measurement of metabolic rate Metabolic rates can be measured using a direct calorimeter. Traditional unit of measurement is calorie, which is the unit needed to increase 1g of water 1oC, a kilocalorie is kcal or C. Measurement of energy is joule (J). A watt is 1 J/s. 1 cal=4.186J Indirect measurements of metabolic rate use the rate of O2 consumption. Direct calorimetry—quantifies heat and external work. Are the gold standard of measurement because they relate to the trait being studied. Indirect measurement would measure O2 consumption. This is used because it is easier to measure but there are uncertainties of 1-5% that can be introduced. Lavoisier used a simple device to measure metabolic rate. Used ice to measure the amount of heat leaving the animal’s body and collected the melted water and measured it. He knew the amount of heat it took to melt ice. Measurement of external work should be included, however this is not necessary if the animal is at rest. If the animal is producing external work it is often enough to measure the heat produced by doing that workDirect calorimetry—quantifies heat and external work. Are the gold standard of measurement because they relate to the trait being studied. Indirect measurement would measure O2 consumption. This is used because it is easier to measure but there are uncertainties of 1-5% that can be introduced. Lavoisier used a simple device to measure metabolic rate. Used ice to measure the amount of heat leaving the animal’s body and collected the melted water and measured it. He knew the amount of heat it took to melt ice. Measurement of external work should be included, however this is not necessary if the animal is at rest. If the animal is producing external work it is often enough to measure the heat produced by doing that work

    14. Fig. 6.4 Lavoisier’s direct calorimeter

    15. Indirect calorimeter Open respirometer a precision instrument used to measure gas exchange. O2 is measured as it goes into and out of the chamber using a paramagnetic or electrochemical cell. It measures the volume of air and percentage of O2. It is very sensitive and can monitor minute by minute changes. Closed respirometer AS the animal uses O2 the CO2 absorbent takes it up and air pressure decreases, causing the fluid levels in the manometer to rise on the left side. At intervals O2 is added into the chamber. The amount of O2 injected equals the amount the animals has used.Open respirometer a precision instrument used to measure gas exchange. O2 is measured as it goes into and out of the chamber using a paramagnetic or electrochemical cell. It measures the volume of air and percentage of O2. It is very sensitive and can monitor minute by minute changes. Closed respirometer AS the animal uses O2 the CO2 absorbent takes it up and air pressure decreases, causing the fluid levels in the manometer to rise on the left side. At intervals O2 is added into the chamber. The amount of O2 injected equals the amount the animals has used.

    16. anphys-tab-05-03-0.jpg anphys-tab-05-03-0.jpg

    17. Injestion of food and metabolic rate The increase in metabolic rate caused by food ingestion is called specific dynamic action (SDA) or the heat increment of feeding. Magnitude of the increase is the total excess metabolic heat produced by the meal. The SDA is proportional to the food eaten and it rises after food absorption, particularly proteins. Diet can induce chronic changes in metabolic rate—diet induced thermogenesis (DIT).

    18. Figure 6.5 Specific dynamic action (Part 1) Specific dynamic action is the calorigenic effect of ingested food. anphys-fig-05-05-1.jpg A certain amount of the meal is degraded to heat in processing the meal. The rest of the energy released can be used for physiological functions. anphys-fig-05-05-1.jpgA certain amount of the meal is degraded to heat in processing the meal. The rest of the energy released can be used for physiological functions.

    19. Figure 6.5 Specific dynamic action (Part 2) SDA is proportional to the amount of food eaten anphys-fig-05-05-2.jpg anphys-fig-05-05-2.jpg

    20. Basal metabolic rate (BMR) and standard metabolic rate (SMR) BMR applies to homeotherms and is the animal’s metabolic rate while it is in its Thermoneutral zone—the temperature zone within which metabolic rate is minimal Fasting Resting SMR applies to poikilotherms and is the animal’s metabolic rate while it is Fasting Resting Routine metabolic rate is used by fish physiologist because of the constant motion of fish.

    21. Figure 6.6 The effect of body size on weekly food requirements The energy needs of an organism are NOT proportional to their body size. anphys-fig-05-06-0.jpg Amount of food consumed in one weekanphys-fig-05-06-0.jpgAmount of food consumed in one week

    22. Figure 6.7 BMR as a function of body weight in various species of placental mammals anphys-fig-05-07-0.jpg anphys-fig-05-07-0.jpg

    23. Figure 6.8 Weight-specific BMR as a function of body weight in various species anphys-fig-05-08-0.jpg Graph on placental animals Smaller animals have a higher weight specific BMR than larger animals. The value b is the same in crustaceans, fish, mammals. Commonly it is between 0.65 and 0.75 and it is nearly always between 0.6 and 0.9anphys-fig-05-08-0.jpgGraph on placental animals Smaller animals have a higher weight specific BMR than larger animals. The value b is the same in crustaceans, fish, mammals. Commonly it is between 0.65 and 0.75 and it is nearly always between 0.6 and 0.9

    24. Figure 6.9 Weight-specific metabolic rate as a function of body weight in four groups of vertebrates anphys-fig-05-09-0.jpg Weight specific resting metabolism is derived by dividing both sides by W, the exponent becomes (b-1) which makes it roughly -0.3. Metabolic intensities vary. IN vertebrates and some invertebrates, exerciese induced increases in metabolism tend to be about 10 times higher than in resting metabolic rate. Mmax=a’Wb’ In this instance b is generally elevated above the typical 0.7 to 0.85anphys-fig-05-09-0.jpgWeight specific resting metabolism is derived by dividing both sides by W, the exponent becomes (b-1) which makes it roughly -0.3. Metabolic intensities vary. IN vertebrates and some invertebrates, exerciese induced increases in metabolism tend to be about 10 times higher than in resting metabolic rate. Mmax=a’Wb’ In this instance b is generally elevated above the typical 0.7 to 0.85

    25. Figure 6.10 Metabolic rate and body weight are related linearly on log–log coordinates (Part 1) anphys-fig-05-10-1.jpg anphys-fig-05-10-1.jpg

    26. Figure 6.10 Metabolic rate and body weight are related linearly on log–log coordinates (Part 2) anphys-fig-05-10-2.jpg anphys-fig-05-10-2.jpg

    27. Physiological and ecological implications of metabolic rate-body weight Cellular properties differ allometrically, particularly in reference to density of mitochondria. Resting heart rate and breathing rates differs allometrically. The structure of ecosystems is affected by allometric relations. Ex: a square kilometer can support 95kg of warthogs, or 460kg of zebras, or 1250kgs of elephants. Environmental pollutants are concentrated in animals with a higher weight specific metabolic rate. Catabolism and excretion are higher in small species. There are more mitochondria in small species per unit of tissue than in large species. Mice breath about 100 times per minute and humans 12 breaths per min Example from book—3500 mice at 20 g each = 1 70,000g deer, however the metabolic needs of mice are greater thus metabolically the same area that supports a deer would only support 440 mice. Drug rates are also affected by metabolism. Higher doses may be needed in smaller species to achieve the same effect.There are more mitochondria in small species per unit of tissue than in large species. Mice breath about 100 times per minute and humans 12 breaths per min Example from book—3500 mice at 20 g each = 1 70,000g deer, however the metabolic needs of mice are greater thus metabolically the same area that supports a deer would only support 440 mice. Drug rates are also affected by metabolism. Higher doses may be needed in smaller species to achieve the same effect.

    28. anphys-tab-05-04-0.jpg anphys-tab-05-04-0.jpg

    29. Fig. 6.1 Proportionality of heart to body size

    30. Figure 6.12 Herbivores of different body sizes coexisting on an African grassland anphys-fig-05-11-0.jpg anphys-fig-05-11-0.jpg

    31. anphys-tab-05-05-0.jpg anphys-tab-05-05-0.jpg

    32. Rubner’s surface law Surface areas increase only as the 2/3 power of their volume. The ratio of surface area to volume declines as organisms increase in size Theories to explain the allometric relation between metabolic rate and body weight Allometries may be manifestations of fundamental or universal organizing principles of life. First theory appeared in the 20th century.Allometries may be manifestations of fundamental or universal organizing principles of life. First theory appeared in the 20th century.

    33. Rubner’s Logic Rubner’s logic rested on data from homeotherms Homeotherms tend to lose body heat to the environment Heat loss is proportional to the animals body-surface. Small homeotherms with a large surface area to volume lose heat more rapidly. An increase in metabolic processes is required for small homeotherms to maintain body temperature.

    34. Problems with Rubner’s surface law Data contradicted the law—the law predicts an exponent of 0.67 and the exponent is significantly higher 0.7 Allometric relationships are also found among poikilotherms and the law only accounts for homeotherms. The explanation for the allometric relationship between metabolism and body weight should include all organisms

    35. Figure 6.13 Theories to explain the allometric relation between metabolic rate and body weight (1) Allometric relations are the result of key internal transport systems, which bring in the raw materials of metabolism. Rates of transport are constrained by geometry. anphys-fig-05-12-1.jpg The transport of O2 and metabolic fuels is constrained by the transport systems within an organism. The larger an organism the more branched and elaborate the transport system. Theory is based on a computer model that examines how the constraints of fractal geometry can be used to explain the transport systems in animals of different sizes. The allometric exponent is computed to be 0.75. This theory can also be used with plants as well as animals.anphys-fig-05-12-1.jpgThe transport of O2 and metabolic fuels is constrained by the transport systems within an organism. The larger an organism the more branched and elaborate the transport system. Theory is based on a computer model that examines how the constraints of fractal geometry can be used to explain the transport systems in animals of different sizes. The allometric exponent is computed to be 0.75. This theory can also be used with plants as well as animals.

    36. Figure 5.12 Theories to explain the allometric relation between metabolic rate and body weight (2) Multiple causes theory states that the rate of any major processes depends on the interaction between multiple underlying processes. anphys-fig-05-12-2.jpg This is based on hierarchical models of how metabolic processes are controlled. This model can explain the shifts that occur when there is an increase in metabolic rate. In this instance other processes that had negligible effects before now have a larger effect.anphys-fig-05-12-2.jpgThis is based on hierarchical models of how metabolic processes are controlled. This model can explain the shifts that occur when there is an increase in metabolic rate. In this instance other processes that had negligible effects before now have a larger effect.

    37. Energetic efficiency Lipids are twice as high in energy density as proteins and carbohydrates. The efficiency of energy absorption = absorbed energy/ingested energy Absorbed energy is available for metabolism Not all energy is absorbed. Growing animals accumulate chemical-bond energy in their body.

    38. Figure 6.14 Net growth efficiency during each year of life in Pacific sardines (Sardinops sagax) Energy absorption efficiency= absorbed energy/ingested energy Gross Growth efficiency= chemical-bond energy of tissue added in net fashion by growth/ingested energy Net growth efficiency=chemical-bond energy of tissue added in net fashion by growth/absorbed energy Growth efficiency declines with age. Broiler chickens are slaughtered at 2 to 3 months because they are meaty at that age and are at peak growth efficiency.Energy absorption efficiency= absorbed energy/ingested energy Gross Growth efficiency= chemical-bond energy of tissue added in net fashion by growth/ingested energy Net growth efficiency=chemical-bond energy of tissue added in net fashion by growth/absorbed energy Growth efficiency declines with age. Broiler chickens are slaughtered at 2 to 3 months because they are meaty at that age and are at peak growth efficiency.

    39. Energy is the common currency of life. Most processes can be expressed in units of energy. The impact of organisms on the ecosystem can be determined by examining energy costs of organisms. Energy of mental effort? Resting brain consumes 20% of the energy absorbed. Francis Benedict determined the working brain did not consume more energy. is this still a good study? Energy functions in animal growth, body maintenance, migration, photosynthesis, building construction, automobile operation, ecosystem degradation and war. Study of individual systems is straightforward but integrating information is not. Energy can function as a common currency in which all operative processes can be expressed. Operations can be compared, subtracted, added, multiplied, etc. In individuals many functions can be expressed in terms of energy—growth, running, nerve conduction, blood circulation, tissue repair and thermoregulation. Theses functions can be expressed on units of energy. At the heart of all these processes is the energy that is released from the ATP molecule.Energy functions in animal growth, body maintenance, migration, photosynthesis, building construction, automobile operation, ecosystem degradation and war. Study of individual systems is straightforward but integrating information is not. Energy can function as a common currency in which all operative processes can be expressed. Operations can be compared, subtracted, added, multiplied, etc. In individuals many functions can be expressed in terms of energy—growth, running, nerve conduction, blood circulation, tissue repair and thermoregulation. Theses functions can be expressed on units of energy. At the heart of all these processes is the energy that is released from the ATP molecule.

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