1. Animal Form and Function (Ch. 40) Jackrabbit Tuna Penguin Seal

2. Animal form and function correlated at all levels of organisation (morphology, physiology, cell biology, behaviour) Physical laws (mechanical strength, diffusion, heat exchange) constrain body ‘design’ and lead to similar solutions to similar problems = convergent evolution (Fig. 4.2) Increasing complexity of large, multicellular animals imposes additional “design constraints” on body form and function Specialisation of cells/tissues Transport systems (vascular, digestive system) Control/coordination systems (hormonal, electrical) Allows for maintenance of homeostasis Thermoregulation: an example of homeostasis integrating form, function (physiology) and behaviour Metabolic rate (overall energy requirement) varies with size, activity and environment Animal Form and Function – basic concepts

3. All animals exchange materials (nutrients, gases, wastes, heat, etc) with the environment Fig. 40.3 1.5 mm (b) Two layers of cells Exchange Gastrovascular cavity Exchange 0.15 mm (a) Single cell - ‘easy’ for v. small or ‘simple’ animals - large surface area - v. small diffusion distances Hydra: a coelenterate (jellyfishes)

4. More complex, multicellular organisms require other solutions for exchange with the environment As cell number (i.e. body mass/size) increases surface area:volume ratio decreases distance between cells and environment increases Specialised branched or folded surfaces allow for sufficient exchange w/ environment (gut, lungs/gills, kidney) – internal (protected), v. extensive Specialised transport systems (e.g. digestive and respiratory system) and internal, interstitial fluid links each cell with environment

5. Internal exchange surfaces (and transport systems) in complex animals (Fig. 40.4) 0.5 cm Nutrients Digestive system Lining of small intestine Mouth Food External environment Animal body CO 2 O2O2 Circulatory system Heart Respiratory system Cells Interstitial fluid Excretory system Anus Unabsorbed matter (feces) Metabolic waste products (nitrogenous waste) Kidney tubules 10 µm 50 µm Lung tissue

6. Hierarchical organisation of complex animals (Specialised) cells are organised into tissues; where many cells have common appearance and function. Four main tissue types (Fig. 40.5) Different tissues are organised into functional units = organs (e.g. heart, kidney) Groups of organs work together as organ systems (circulatory, excretory systems) Table 40.1 Epithelial tissue Nervous tissue Connective tissue Muscle tissue

7. Coordination and control of complex body plans: the role of endocrine system and nervous system Fig. 40.6 Response limited to cells with specific receptors for each signal Stimulus from internal or external environment Response involves changes in membrane potential at specific target cells

8. An animal’s internal environment can be maintained in very different state than external environment Regulators – use internal control mechanisms to regulate and maintain internal environment despite fluctuation in external environment, e.g. thermoregulation, osmoregulation Conformers – allow internal environment to change with change in external environment Fig. 40.7

9. Maintenance of relatively constant internal environment when external environment fluctuates = homeostasis Physiological variables are maintained at or near a particular value called a set point, for example, human body temperature ~37°C small bird body temperature 42-44°C human blood pH 7.4 shark plasma osmolarity 1000 mOsm Many plasma metabolites and ions are regulated at particular values, e.g. glucose, calcium, iron, Na +, K + Homeostasis depends on negative-feedback control loops Positive feedback amplifies a stimulus

10. Non-living example of homeostasis maintained by negative feedback (Fig. 40.8) Set point = value of physiological variable, e.g. 37°C Stimulus = hot, sunny day Thermostat = sensory system Heater = metabolism/activity to ↑ heat (or sweating to ↓ heat) Homeostasis relies on negative feedback loop, a response that reduces or “damps” the stimulus – returning temperature to set point

11. Homeostasis around a “set point” is not fixed or static but can be variable (Fig. 40.8 ) Regulated changes in homeostasis are essential for normal body function = circadian rhythm controlled by biological clock (expressed by hormone melatonin) Fever = a resetting of bodies thermostat to higher set point

12. - the process by which animals maintain an internal body temperature (T body ) within certain range - v. important because physiological/biochemical reaction rates are temperature-sensitive, changing 2-3 fold for every 10°C change in T body Thermoregulation: an example of homeostasis integrating form, physiology and behaviour

13. Thermoregulation requires regulation of heat production and/or exchange with the environment T body = (heat production or heat gain) – (heat loss) Endotherms – heat mainly produced by metabolism (thermogenesis) Ectotherms – heat gain mainly from environment Remember: heat is a by-product of cellular respiration; but endotherms produce much more heat per gram of tissue (and require more fuel/food)

14. Balancing heat gain and loss: the importance of the integument or body surface (Fig. 40.11) Heat exchange between and organism and its environment occurs by 4 physical processes: Conduction Convection Radiation Evaporation Biological adaptations: size, surface area, chemical composition (lipids), exposure (behavioural posture)

15. Mechanisms for regulation of heat gain or heat loss Insulation - reduces heat loss from animal to environment - hair, feathers, fat layers formed by adipose tissue - can be actively regulated (goosebumps!) Circulatory adjustments - regulating blood flow to minimise heat loss from flow of warm blood to body surface Evaporative heat loss, e.g. panting, sweating (licking!) Behavioural responses - e.g. basking, use of warm microhabitats - allows ectotherms to elevate body temperatures to those comparable to endotherms, e.g. lizards

16. 1 3 2 Circulatory adaptations: reduction of heat loss by countercurrent heat exchangers 1 Arteries carrying warm blood from core are in close contact with veins carrying cool blood from periphery 2 Near the end of the leg cooled arterial blood can still transfer heat to the even colder blood in adjacent vein 3 As blood in veins returns to the body core it is now warmed, retaining heat and minimizing heat loss Fig. 40.12

17. Increasing metabolic heat production Endotherms continuously lose heat because their higher Tb is nearly always >> then ambient (environmental) temperature Three main mechanisms: Muscle activity – running, jumping Shivering - antagonistic sets of muscles contract with no net work but lots of heat production Non-shivering thermogenesis (NST) - using brown fat, a tissue specialised for very high rates of heat production Endotherms therefore increase metabolic heat production (thermogenesis) as Ta decreases

18. Some reptiles and insects can be endothermic using muscle contraction to generate heat to maintain high Tb Burmese pythons incubate their eggs Pre-flight warm up of flight muscles in hawkmoth Fig. 40.14 Fig. 40.15

19. Thermoregulation in humans via negative feedback (Fig. 40.16) - Hypothalamic control (thermostat) - Circulatory responses - Shivering - Sweating Check this out!

20. Metabolic rate (MR) = the total amount of energy an animal uses per unit time (Fig. 40.17) - Animals use chemical energy from food (digestion and nutrition) - ATP produced by cellular respiration is used for cellular work, growth, biosynthesis, repair -34% of total energy in any food is converted to ATP or cellular work -56% is “lost” as heat (thermoregulation) “Bioenergetics” = the study of variation in metabolic rate

21. Basal metabolic rate (BMR) = minimum MR in a non-growing endotherm at rest, no digestion, not thermoregulating BMR human male 1600-1800 kcal/day human female 1300-1500 kcal/day Metabolic rate (MR) can be measured in different ways Daily energy expenditure (DEE) = overall total metabolic rate (including activity, growth, reproductive activity, etc) DEE = 2-4 x BMR Fig. 40.20

22. Comparative physiology: “scaling” of metabolic rate and body mass across different species (Fig. 40.19) b = 0.75 BMR for each kg 1 kg of mouse tissue uses much more energy than 1 kg of elephant tissue

23. Hibernation (torpor): abandoning maintenance of high Tb but not abandoning homeostasis (old Fig. 40.21) Belding’s ground squirrel Spermophilus beldingi