1. 24-1 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Chapter 24: Metabolism, temperature regulation and environmental stress

2. Energy requirements and metabolism Energy is required to perform work The rate of energy use for internal and external work is known as metabolic rate. It is expressed as energy expenditure per unit time Aerobic metabolism requires the availability of oxygen Anaerobic metabolism involves the release of chemical energy without the use of oxygen Most animals utilise aerobic metabolism most of the time due to its greater efficiency 24-2 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

3. Factors affecting metabolic rate Body mass Activity Digestive state 24-3 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

4. Body temperature The rates of many physiological processes are determined by temperature Temperature is a critical determinant of the rate of metabolism Animals either thermoconform or thermoregulate; both require body temperature to be kept in optimal range for physiological functions, but this is achieved by different methods Animals exchange heat with their environment through conduction, convection, radiation and evaporation/condensation 24-4 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

5. Fig. 24.2: Heat exchange 24-5 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

6. 24-6 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Stresses of low temperatures Mountain and polar regions are characterised by –low temperatures –increased solar radiation Animals of cold regions are more tolerant of low temperatures than other animals Ice formation damages cells by concentrating cytoplasm and dehydrating proteins

7. 24-7 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Do animals freeze? Animals in areas that experience low temperatures may –avoid freezing by supercooling –tolerate freezing During supercooling, the temperature may drop below 0°C, but ice does not form in the animal’s tissues –body is evacuated of material that might seed ice formation –they produce antifreeze that prevents ice formation and/or lowers freezing point

8. 24-8 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Insects at low temperatures Insect species that live at high altitudes tend to be small and wingless –able to make use of sheltered microhabitats Many species exhibit thermal melanism –dark coloration absorbs heat Basking in the sun increases body temperature –some insects bask on light-coloured flowers that reflect heat

9. 24-9 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Temperature coefficient (Q 10 ) Biochemical processes take place within a range of temperatures –rate of activity increases with temperature Temperature coefficient, Q 10, models the rate of reaction for a 10°C rise in temperature Quantifies effect of temperature on biochemical processes

10. 24-10 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Fig. 24.4: Relationship between processes and temperature

11. 24-11 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Patterns of body temperature regulation Endothermic animals (birds, mammals) maintain a constant body temperature by deriving heat from internal or metabolic processes Ectothermic animals cannot regulate body temperature through those processes, but can reduce fluctuations in body temperature by adjusting behaviour

12. 24-12 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Phenotypic plasticity Some organisms can modify phenotype to accommodate changes in environment –phenotypic plasticity Such changes are categorised as –acclimatisation: accommodating several changes in environment –acclimation: accommodating one change in environment –hardening: acclimation in plants

13. 24-13 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Thermal acclimation Although metabolic processes in ectothermic animals tend to increase with temperature, thermal acclimation means that metabolic rate may change between seasons –cold-water fish may have a higher metabolic rate in winter than they do in summer Seasonal metabolic compensation –different sets of summer and winter enzymes with different optimal temperatures –animals may be more active in winter than summer, despite lower temperature

14. 24-14 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Metabolic depression Facing extreme conditions, many animals undergo a reduction in metabolic rate (metabolic depression) Some organisms can reduce metabolic rate to less than 1% of normal resting metabolic rate Animals survive by dehydrating as larvae or adults, or becoming inactive

15. 24-15 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Hypothermia and torpor Endothermic animals undergo –prolonged hibernation during winter –prolonged aestivation in dry conditions –shorter periods of torpor Body temperature is reset to a lower level –hypothermia –metabolic processes drop as a result –decreased responsiveness to stimuli

16. 24-16 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Risks of torpor Freezing –use of cryoprotectants such as glucose to prevent freezing Lack of oxygen –many animals can tolerate anoxia Exhaustion of energy supply –breakdown of lipids using anaerobic pathways to avoid using O 2 Desiccation

17. 24-17 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Torpor Many small mammals and some birds reduce metabolic rate and enter torpor in response to low temperatures Body temperature is regulated during torpor –if it drops too far, animal becomes active for a period before re-entering torpor Blood flow to skin and extremities is reduced during torpor

18. 24-18 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Fig. 24.13: Rate of O 2 consumption in dunnart

19. 24-19 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Oxygen stress Hypoxia is a decrease in partial pressure of O 2 from normal levels Occurs when rate of O 2 consumption exceeds replenishment –caves, burrows –swamps, water-logged soil –tide pools Occurs at high altitudes where P O 2 is low

20. Fig. 24.16: Burrow ventilation 24-20 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

21. 24-21 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Adaptations to low oxygen Low environmental P O 2 reduces the gradient essential for diffusion of O 2 across membranes Physiological and behavioural characteristics compensate for low P O 2 –tolerance to anoxia –haemoglobin –high erythrocyte counts –low rates of O 2 consumption –burrow ventilation

22. 24-22 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Animals at high altitude Lower partial pressure of oxygen in high altitudes produces altitude hypoxia Hyperventilation is a response to low P O 2 –increases O 2 content Hyperventilation also eliminates CO 2 from body, causing high blood pH Erythrocyte count may increase as a result of acclimation –higher levels of haemoglobin

23. Question 1: High-altitude training is a physiological method used to obtain an increase in haemoglobin. Why would this be referred to as blood doping? Are there any harmful effects? 24-23 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

24. Fig. 24.15: Altitudinal elevation 24-24 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

25. 24-25 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Oxygen stress (cont.) When faced with a thermal gradient, animals have a preferred temperature –behavioural thermoregulation When exposed to hypoxia, animals choose a lower temperature –hypoxia depresses thermogenesis (metabolic heat production) in endotherms –set point of body temperature lowered

26. 24-26 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Oxygen stress (cont.) Reduced temperature decreases metabolic rate (Q 10 effect) Decreased requirement for O 2 Reduction in temperature increases O 2 affinity of haemoglobin Hyperventilation and increased cardiac output are avoided

27. 24-27 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Oxygen stress (cont.) Depression of thermogenesis in response to hypoxia is more common in small animals than in large animals –large animals have a lower mass-specific metabolic rate, so they use proportionately less O 2 to maintain body temperature –smaller surface area in relation to body volume means that large animals do not absorb or lose heat as rapidly

28. 24-28 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Global warming Increase in temperature as a result of global warming may stress less thermally-tolerant organisms –increased sea temperatures have a negative impact on penguin species –migrations of some bird species start earlier in the year –breeding is brought forward or delayed –species’ ranges are extended or retracted

29. Summary Aerobic metabolism requires oxygen and is the most efficient form of metabolism Body mass, activity and digestion are influencing factors of metabolic rate Body temperature is a critical determinant of metabolic rate and other physiological processes Animals exchange heat with their environment Animals may reduce metabolic rate in response to environmental stress 24-29 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University