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Organismal Phys Midterm Summary.docx

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Western University
Biology 2601A/B
Graeme Taylor

Organismal Physiology: Lecture 2: Principles of thermal biology Temperature: Intensity of motion by the atoms in the object Heat: Amount of energy in the object Temperature determines the direction of heat transfer (e.g. warm  cool) e.g. rabbits (image) – loses heat by respiratory and cutaneous evaporation. Gains thermal radiation from all objects in surrounding, and it’s metabolism. Exchanges heat with ground and wind convectionally. Important temperatures: • 0°K = -273.4°C  absolute zero • 50-70°C  most proteins denature • 100°C  some hot springs bacteria still survive Definitions Endotherms: generate internal heat Ectotherms: rely on external temperatures to determine Tb Homeotherms: defend a constant body temperature Poikilotherms: Allow body temperature to vary *Heterotherms: Have more than one temperature set point, or switch between homeo-and pikiothermy *Regional endothermy/heterothermy: different Tb in different parts of the body Relationship between temperature and metabolism in an ectotherm: - M=a10^(nTb)  increasing body temp = exponential increase in metabolism M- Metabolic rate a & n – constants Tb – Body temperature  logM = loga + nTb (Think y = b + mx) Log a – Intercept N – Slope Tb – variable change, that results in change in logM (metabolism) Q10 – Temp. Coefficient – ration of the rate of a process at one temperature over the rate of the same process at a different temperature 10°C lower Q10 = R /TR (T-10) -- b/c the T/metabolic rate relationship is not exactly exponential, the impact of a change in T(x), varies with the temperature - the same relationship of Q10 hold true for plant functions like respiration ~1 – physical/chemical processes ~2-3 for most biological processes How do these temperature changes occur? - Increasing temp = more interactions b/w molecules = more reactions  Temperature also determines the conformation and efficiency of an ezyme (Q=~2-3 bio systems) - warmer = substrate encounters enzyme more often= more reactions - optimal temp for effective change in binding site = increased binding affinity - too hot (over 50°C, or too cold) = weaker binding - want a low Km = high binding affinity - Km – amount of substrate required to reach 50% of Vmax (reaction rate) - is a function of proteins tertiary structure and thus temperature - vs. Kcat – MAX number of molecules enzyme can process at saturation of substrate How does affinity change with temperature? - Affinity too high (low temp.) – enzyme binds too tightly = slow reactions (Km v.low) - too low (high temp.) – enzyme binds too loosely to substrate = reactions less likely to happen Metabolic Rate: an animal’s rate of energy consumption; the rate at which it converts chemical- bond energy to heat and external work  this rate is determined by enzyme activity thus, temperature dependant Lots of processes in ectotherms are governed by temperature: activity levels, muscle contraction, locomotive speed, digestion, growth, germination, photosynthesis, fruit production and ripening. - temperature is a fickle cue; plants and animals use more reliable cues like photoperiod to govern their seasonality Thermal Intertia: - low surface area to volume ratio = more energy - retain more heat - heat takes longer to dissipate b/c low S.A Animal tolerance of declines at temperature limits, as it causes: What happens at temperature limits? What can be done about it? Freezing - prevent ice formation - prevent damage from freezing Mismatch of O2 demand and delivery - alter aerobic cardiovascular capacity Increased membrane fluidity (with increased - modify membrane to be: temperature) - more fluid @ low temp. to compensate - less fluid @ high temp Enzyme denaturation - use chaperone (heat-shock proteins) - change the enzyme – the same relationship with Q10 holds true for plant functions like respiration. Acclimation can help offset this response!! Across species from the tropics to the poles, there is a normal range for body temperature (at different temperature); which coincides with the recommended substrate affinity.  how do all these animals have the same enzyme, with the same enzyme-substrate affinity but function at different temperatures? - they have different molecular forms of the same enzyme – evolutionized to survive @ that tmp. Even between closely-related species, with slight differences in temperature, they will evolutionarily adapt by having different enzyme homologs to maintain that same high enzyme- substrate affinity. Lecture 3: Temperature 2: Plants and Ectotherms - animals are able to maintain temperatures much higher than their surroundings What if you are an ectotherm?? – does not generate internal vs. poikilotherm – animals who’s body temp. is determined by environement temp. - going with the flow is better in some environments than others (e.g. rainforest) - however in extreme environments (e.g. dessert) – are ectotherms passive victims of their thermal environments? Organism stays the same temperature when… Radiation (R) + Convection (H) + conductance (C) + Latent Heat (L) + Metabolism = 0 Radiation: ability to minimize (cool)/ maximize (warm) via radiation e.g. change by leaf color or angle H – Convection: e.g. change by leaf shape C- conductance (b/w solids): e.g. not much of an issue for plants L – latent heat exchange: e.g. transpiration M –metabolism: e.g. metabolic heat generation in some plants Plants can affect their leaf temperature: - leaf color alters radiation absorption - long-term, adaptive response(black absorbs more heat – b/c less reflectance) Behavioural thermoregulation: - rolling leaves and pointing them vertically reduces sun interception saving water (e.g. corn leaves) - animals do this too by moving - plants can also affect their leaf temperature (shape affect convection – heat exchange with air molecules) - Plants can affect their leaf temperature - latent heat of vaporisation of water 2270kJ/kg - transpiration is a very effective way to cool if you have water. Evaporation in the Chihahuan desert –e.g. 40°C plant vs. 50°C environment (enzymes denature) (difference between life and death) What about metabolism? Where does ectotherm heat come from? - in plants – futile cycling in mitochondria - in animals – muscle contractions Some plants can produce their own heat (endothermic plants) Endotherm in skunk cabbage and other araceae – Why do plants need metabolic heat? - to warm up tissues to a more optimal physiological temperature - to attract pollinators in early spring: - increased ordo diffusion - provides warmth to ectothermic pollinators e.g. thermogenesis in the aroid spadix - notice that their e-transport chain is not inhibited by CO, cyanide or azide - have an alternative oxidase pathway to produce heat (instead of ATP) - CN – insensitive respiration in plants Heat generation in flight muscles of bees and moths (endothermic, homeothermic insects): - maintain a cruicial core thoracic temperature - low temperatures = shivering of thoracic muscles + decreased heat loss - high temperature = use heat from environment; +increased heat loss * important for flight and brooding young Why fish are ectotherms (can’t produce internal heat) - fish can generate heat – like anything with metabolism – but they have problems keeping it - why? b/c surrounded by thermally conductive water (would strip its heat away anyways) NEW DEFN: Ectotherms don’t generate internal heat that contributes meaningfully to body temperature - fish gills act as heat sinks - fish are ectotherms bc the high blood flow across their large gill surface means that they lose heat to the environment really quickly. - heat retention is a major issue e.g. notice that there is regional endothermy in tuna (31°C @ core, 19°C @ periphery) Rete mirable: REGIONAL ECTOTHERMY - use countercurrent heat exchange within the body – V. effective – short circuits heat from arteries to veins - a recurring theme especially in but not restricted to fish Also seen in: swin bladed, heater organs, O2 delivery to retina  Allows for very effective heat exchange within the body IN CERTAIN FISH (have warm interiors e.g. tuna, sharks): rete seen extending outwards from core, where venous blood flows outwards and transfers it’s heat to the arteries going inwards Rete is found in the RED MUSCLE! – thus red muscle temperature is elevated above water temperature -- red muscle is typically found in animals with greater thermal mass (can keep the heat within them bc of thermal inertia?) Where does the heat come from? - heat comes from the normal heat produced by contractile activity of the red muscle - the only difference is tha the heat is retained via rete mirable effect WHY? - to allow migration through water of different temperatures - to allow better performance as a predator chasing prey into colder water - improvements in power output of muscle - large sharks are also regional endotherms; convergent trait – thus is v. important/helpful to fish Lecture 5: Insect Cold-tolerance - animals can sense a change in season with shorter days, and temperature changes; and they know they need to prepare with this - the way they deal with these changes in temperature are by changing their: - behaviour - physiology - other biochemical aspects As compared to us, we change our behavior -endotherms: are able to regulate their own body temperature by producing heat, and keeping their body pretty steady. - e.g. we have shelter - e.g. birds: go south for the winter, Canada geese are causing a big problem in the south - e.g. foxes: use fur as insulation Another insulation = fat, same with birds; tuft out feathers and gain weight - many animals go into torpor or hibernation… lower their metabolic rate to get through the cold - ectotherms: relies on the xternal environment; body temp mimick the xternal environment - e.g. insects; their bodies will go down to low temps with cold temp outside. - insects are important bc – most successful terrestrial animal. – only place insects are not found is in the oceans.. – important pollinators (e.g. crisis with decrease in honey bees) – they are the main pollinators of our food.. - rely on them as a biological control (some are pest species – or pest controls – can be used against each other) - parasitoids; e.g. wasps (often) – lay their eggs in pest species – e.g. in a pest caterpillar – inhibits eating - gain a lot of products (silk, honey) and food from them - as an insect they have to deal with a lot of daily, and seasonal temperature differences - metabolic rate increases with temperature and decreases with decreased temp. - temperature brings enzyme differences etc. - insects have adapted in a lot of ways 1. they can leave: e.g. monarch butterfly – flight path down south like birds and overwinter there. 2. get creative – e.g. outline of honeybees – their thermal profile show that they stick around for the winter and need to keep warm. The red part—thorax is vey red on the thermal profile, use a mechanism to unhinge their wings near the thorax where they are attached and vibrate their wings to become endothermic. 3. get cold – prepare for it: - eat lots before winter and store your fat: put on nutrient reserves when there are none available - stop growing: very metabolically costly - stop reproducing: very costly$$ - find the right overwintering site Pic: mosquito of west nile disease – puts on a lot of fat – has a lot fat cells of adipose tissue in liver Vs. other mosquito – much skinnier Pic: in the field – air temp is -15Cdegrees, other insects that survive there. e.g. the gall of a goldenrod; big mass of tissue that worms around a larvae. Other insects that survive under the insulating snow.. wooly bear caterpillar hangs out there Further down in soil there is temp (0.5C) – burrow a bit into ground (e.g. acorn needle??) – stay unfrozen in the warm soil Why is bein cold so bad? – uncomfortable? – why is it so bad for an insect? - chilling injury: being cold and having damage to the cells without actually freezing: - loss of membrane fluididty and loss of ion homeostasis - disrupts the membrane processes (e.g. transporting) – integrity of the cell is compromised - loss of ion homeo – reduces muscle function and cause cell death - freezing injury: ice crystal formation - death!: ultimately lead to it, if too much damage is sustained Pic: live flurosescent staining: red = trashed, is of the gut of an insect kept warm vs. cold - lots of cells died in the cold one (more red) Why freezing could suck.. - when frozen, water: becomes solid and expands - thus very damaging in organisms 3 classification of cold tolerance: 1. die before freezing – chill susceptible (will die before freezing, most insects, fruit flies etc.) - need to keep warm (e.g. go underground, fly south) 2. Keep from freezing – Freeze avoiding - lower freezing point (okay with being cold but can’t freeze, they can keep from freezing, or lower the point at which they freeze) 3. Survive freezing – Free tolerant (can survive freezing of the extracellular fluid in their bodies) - be a general bad-ass Temperature on y and time on x, the bump in the graph  when something freezes it actually releases heat, to tell if something freezes, we look for the point that shows the supercooling point.. aka. The freezing point At the top there is body temp, with the range where they have normal activity - as soon as you start cooling it = cold shock.. chill susceptible - then freeze avoidant insects there (supercooled insects are similar) - then further down are freeze tolerant insects that can handle it. - graph shows works with gall flies and observes that they survive at freezing temps. Freeze-avoidant insects - don’t want to freeze but how? - change the point at which you freeze! Supercooling: typically thought that water needs to be a 0degrees to start freezing - but really small droplets, can go down to -18 degrees before they start freezing - e.g. put a bottle of Fiji water in.. but it will still be liquid even though it’s frozen till hit.. water that is supercooled needs a site of recrystalizaiton to start a site where the lattice of ice can form - freeze-avoidant insects - mask ice nucleators; eveacuate the gut of food and anything that can freeze – just flush it out - or mask it, anything that can start the nucleaization process Prevents ice growth: use antifreezing properties/substances - prevent recrystallization: have ice crystals and they will get worse (thus want to reduce this the most! ) - free-tolerant insects: may want to freeze, but don’t want huge ice crystals in them - prevent recrystallization - REAL WORLD APPLICATION: Ice nucleating agents and pest controltake advantage of these strategies and turn them against them e.g. rusty grain beetle  pest species of grains - they are freeze avoiders, so if they are getting rid of gut bacteria… what we do is make that an give it to them, which causes them to freeze and die. - topical application of ice nucleators - microorganisms - cause ice formation  death Cyroprotectants: -- it’s own antifreeze - glycerol, sorbitol, trhalose (carbs or polyols) made of all these - antifreezes! 2 different ways they can be used: 1. - colligative properties (for freeze-avoiders) – use them for this - freezing point depression based on number of solutes in solution 2. - non-colligative properties (for freeze tolerators) – use them for this, want to freeze/ can, just need protection against ice formation - protect membranes, enzymes during freezing Emerald Ash Borer-sicle: - another type of species – destroys ash, and really needs to be kept in control as it is a pest species - many are working on researching on how they tolerant overwinteritng, and if they produce cyroprotectants (produce so many 25% -- they taste sweet bc of all the carbs in them) A how-to-guide for freezing - draw water out of cells (water is what freezes, and don’t want organelles to be susceptible to freezing vs. extracellular fluids.. which don’t mind freezing as much) - keep the ice nucleators - only freeze extracellular fluids - freeze at a higher temperature (e.g. dropping something in liquid nitrogen 80degrees – will freeze instantly, however, something in water at -5 will take longer, thus for an insect – they want to freeze slowly, don’t want to flash freeze and disrupt cells, want to control the freezing process - the in end icecrystals form outside of the cell instead Rapid Cold Hardening - prior exposure to cold enhances protection against more cold - produce cyroprotectants - stabalize membranes (increase fluidity) -- if you expose an insect to a mild low temp and then a more extreme one it survives very well. - pic: gut: cells stained red= dead, green = alive. Both pics, both exposed to -8, and one expose to 0degrees prior to that .. the one in the bottom exposed prio, had more survived cells b/c produce cyroprotectants and stabilize membranes Some like it cold - sometimes colder is better! - metabolism + nutrient reserves - if you walk though the forest in winter, the gall in crossection, there are larvae poking out - what they found is if you kept them warmer in the winter, they didn’t live as long, and weren’t as reproductive - being warmer, their metabolism is faster, use up all the nutrients in the gall, being colder allows them to thus have more nutrient supply, lower metabolism and thus survive longer. Other freeze-tolerant critters: - some invertebrates: - Siberian salamander - some earthworms - some barnacles - some mussels - painted turtle hatchlings (vertebrate) - European wall lizard - wood frog  Why do we care? - one of the big things today is climate change, and winter is where they are usually most affected TOP MAP: precipitation BOTTOM MAP: temperature  know insects can survive winter, and some like it cold, so what are something that happen, with areas of different precipitation (=different snow cover) Repeated freezing and thawing: - repeating cold exposure  map of temperature on the y axis over time (months on x axis) – line of temp goes up and down up and down over 0 degrees = repeated freezing and thawing in winter VERY BAD – one long cold exposure is ok, however repeated thawing results in damage, and insect survival is decreased, might reproduce less PIC. Different seasons – theme seasonal adaptations and how they deal with it - insects fluctuate with their environment yet are the most accessible types of terrestrial animals, - think how they adapt, to what extent, and what makes them so adapt. They way they deal with temperature stress and Lecture 6: Metabolism 1: Photosynthesis: Autotrophs: make food from sunlight and other energy sources Heterotrophs: (eat the autotrophs) use the food to do work - we are obviously heterotrophs dependant on the activity of autotrophs in our planet Problem: graph: increase over previous decades in the yield of rice globally. The 3 most largest countries of producing rice (China, India, Indonesia). Considering the green revolution in the 70’s, we optimized morphology, nutrition, and fertilizers, and gain upto40% from the previous decades, however that has been declining, in the 2000,s there was no more increase in yield that could be gotten from the previous decades, and is projected to continue. Problem: growing population and decrease in rice yield. How do we feed them?! - we’ve increased all sources: optimum water and fertilizer, increased how we use them, there is not much to increase their productivity * could increase their photosynthetic ability – area of active research Photosynthesis: the most important biological process on earth - chlorophyll concentrations: 164*10^12 kgC/year (165 billion Tonnes** carbon exchange per year) - cold water stores lots of nutrients where there is a lot of sun - terrestrial – normal ndbi – how much photosynthesis / area is happening e.g. no PS in dessert of sahara vs. amazon - the amount of CO2 fixed by photosynthesis usually dwarfs the amount used by fossil fuel etc. Climate change, rise of CO2 and increase in temps Plot from Hawaii, this year we have passed 400part per million (400ppm) - the line can be seen to wiggle, which is the annual cycle – where every spring they take and draw away the CO2, and later in winter respire it all out and they go up Photsyntesis is driven by light = energy - so light has a wavelength, but photons have energy dependant on that wavelength, - visible spectrum of light, blue or violet = more energy vs. red - photons are absorbed by pigment, usually which has a color, indicative of what they reflect - the absorption of a photon excites that molecule Pigments: - molecules that absorb photons - generally coloured (the reflected wavelengths) - absorption of the photon increase the energy level of the molecule - the ground state – when not excited by any energy - when is absorbs a red photon  goes to the lower energy excited state - when it absorbs a blue photon  goes to a slightly higher state, and emits some heat releasing some energy and falls to the red excitation energy  which is the energy then used to drive photosynthesis - wavelength of light, there are peaks for the red and blue - red = light absorbance spectrum of a leaf (/ pigment in leaf) - blue = O2 evolution rate/action spectrum (/ relative rate of phot
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