TEMPERATURE.

TEMPERATURE

Vertebrates can tolerate only a small portion of this range.
350 oC (662 F) Prokaryotes (bacteria, cyanobacteria) span almost the entire range of Earth’s Temperatures. Vertebrates can tolerate only a small portion of this range. Deep sea Hydrothermal vents Why should we care about environmental temperature? Few Species of Fish 44 oC 0 oC (32 F) Large Polar Mammals -60 oC -89 oC -128 F Antarctica

Temperature sets limits…
Environment Physiology Morphology Behavior performance Darwinian fitness

Limits at the Cellular Level
Increased Temperature speeds up biochemical reactions… …to a point Biochemical structures (i.e. enzymes) breakdown Rate of reaction Increasing T Temperature is a measure of Heat or Kinetic Energy (How fast are the molecules moving) Faster more molecules collide with enough energy to activate the reaction, Too fast and the molecules themselves start vibrating apart. But this curve is species specific…temperature doesn’t affect all animals in a similar way…

… but limits are species-specific
Temperature Performance Thermal performance curves: specialist generalist Lower lethal temp What happens where line ends? Upper lethal temp

Temperature Outline Definitions: Extreme Temperature: HEAT
Heat Transfer Physiological strategy: endo, ecto, etc. Temperature tolerance Extreme Temperature: HEAT Death? Avoidance strategies Tolerance strategies Extreme Temperature: COLD Example: Camels are cool!

Temperature Basics Heat Transfer Thermal Strategies Thermal Tolerance

Heat transfer between animals and environment

What’s the difference between temperature & heat?
Measure of intensity of heat (oC, oF, K) Total KE (calories or joules) 1 Calorie = energy required to raise 1g of water 1o C How many calories to heat 1g water from 25o C to 50o C? Same temp, Different heat content = 25 calories How many calories to heat 100g water from 25o C to 50o C? = 2500 calories

Body temperature depends on heat stored
Heat production (metabolism) + Heat in - Heat out = Heat stored Gains > losses

4 Mechanisms of heat transfer
Conduction Conduction + Convection Radiation Evaporation “The Rules” Heat flows from warmer cooler Greater temperature gradient, greater flux Physical properties matter

1. Conduction • conductivity of materials
= heat transfer between bodies in direct physical contact temperature differential area of contact • conductivity of materials

Boundary Layer is Removed
2. Convection = bulk movement of fluid - Accelerates heat transfer between a solid and a fluid Why? Hot object CONDUCTION ONLY Hot object CONDUCTION AND CONVECTION So what is ‘boundary layer?’ Boundary Layer is Removed

Distance from solid surface
2. Convection …All fluids come to rest at a solid surface Air reaches full speed Air reaches full speed = “boundary layer” Fluid speed Distance from solid surface Size of boundary layer is influenced by: Thicker boundary layer, less heat loss to conduction size (and shape) of animal surface roughness fluid speed (air, H2O)

3. Radiation = transfer of heat between objects without contact ∞
Short wavelengths Above absolute zero, all objects emit & receive radiation Surface temperature is important: Intensity = rate of photon flux = number of photons hitting an area per unit time ∞ -intensity T4 Long wavelengths -hotter surface, shorter wavelengths Area of radiative surface is, too

@ 35o C, it takes 580 cal to vaporize 1g of H2O!
4. Evaporation =Extremely effective method of losing heat @ 35o C, it takes 580 cal to vaporize 1g of H2O! exposure of moist surfaces moisture gradient

Heat flux from different sources is additive
Infrared thermal radiation from lizard Direct sunlight Infrared thermal radiation from atmosphere Convection by wind Evaporation Conduction from rock Write on board: Heat Production (metabolism) + HEAT IN (red arrows) – HEAT OUT (blue arrows) = HEAT STORED = body temp Infrared thermal radiation from rock

Temperature Basics Heat Transfer Thermal Strategies Thermal Tolerance
Conduction Convection Radiation Evaporation Thermal Strategies Thermal Tolerance

Thermal Strategies Ectotherms: a body temperature principally dependent on external heat sources Endotherms: a body temperature principally dependent on internally generated metabolic heat Homeotherms: body temperature kept constant Poikilotherms: body temperature varies Poikilo means ‘change’ in greek

Ta Tb MR ENDOTHERMS POIKILOTHERMY HOMEOTHERMY ECTOTHERMS Ta Tb MR
Terrestrial Birds and Mammals Some small birds and mammals Brooding Python A few fish POIKILOTHERMY HOMEOTHERMY Polar Marine Fish Most Amphibians and Reptiles A few Amph and Rept Freshwater Fish Most Marine Fish Endothermy: generate internal heat through metabolism Ectothermy: Obtain heat from the environment Start with: TERRESTRIAL BIRDS AND MAMMALS—where are they, why? Then: AMPHIBIANS AND REPTILES? Where and why? Then point 1: so, where are freshwater fish? (more poikilothermic) Then point 2: so where are marine fish? Polar fish? Then point 3: so where are the behavioral thermoregulators Then point 4: python and tuna Lastly, point 5: where are torpid mammals and birds? Points to make: Air conducts heat less well than water, so if water experiences large temperature extremes, so will aquatic animals; that is, aquatic animals are subject to the fluctuations in the water around them But, large bodies of water chage temp very little (water has high heat capacity, so it takes A LOT of heat to change temp of a large body of water) So, streams change temp drastically (low volume) Oceans don’t change temp very much Arctic and antarctic seas don’t change at all Some ectotherms can behaviorally regulate temperature..where does that put them? Some ‘ectotherms’ can produce internal heat (brooding python; marine fish—tuna) Some endotherms experience heterothermy Last: I want you to think about the relationship between ambient temperature and metabolic rate: differs greatly between endotherms and ectotherms. Endotherms change metabolic rate to regulate body temp Ectotherms can increase metabolic rate as body temp goes up ECTOTHERMS Ta Tb MR

Conduction Convection Radiation Evaporation Thermal Strategies Endotherm vs Ectotherm Homeothermy vs Poikilothermy Thermal Tolerance

Thermal performance curves:
Preferred Body Temp Performance What happens where line ends? Temperature

Preferred Body Temp Performance What happens where line ends? Temperature Environmental Temperature shift? ACCLIMITIZATION!!

Temperature Tolerance
Acclimitization Biochemical Membrane dynamics Enzyme types and concentrations Heat Shock Proteins Behavioral Morphological Physiological Will discuss in hot vs. cold

Membrane Dynamics What are the kinks?
Membranes can be ‘fluid’ or ‘viscous’ ‘Saturated’ refers to the number of hydrogens present. if there is a double bond present, the fatty acid is not ‘saturated’ with hydrogen atoms if there is no double bond (every oxygen has Saturated and Unsaturated Fatty Acids Saturated Fatty Acid: These are fatty acids which contain the maximum possible number of hydrogen atoms. That is each carbon in the chain has two hydrogen atoms attached to it. It is "saturated" with hydrogen atoms. Unsaturated Fatty Acid: These are fatty acids which contain carbon-to-carbon "double" bonds. Therefore since a carbon atom can have only 4 covalent bonds, there is one less bond available for hydrogen, therefore there is one less hydrogen. (The carbons are not "saturated" with hydrogen atoms.) What are the kinks?

Polyunsaturated Fatty Acid (Omega 6)
Why is butter so hard at room temp? (straight saturated chains pack together well, make fats more viscous) Why is oil liquid at room temp? (kinked chains are less packed together, more fluid) that’s also why unsaturated fatty acids are better for you. They are less likely to form plaques and block arteries (they don’t pack together that well). Kinks are in the hydrocarbon chain The bent shape of the essential fatty acids keeps them from dissolving into each other. They are slippery and will not clog arteries like the sticky straight shaped saturated fats and the trans-fatty acids found in cooking oils and shortenings that are made by subjecting polyunsaturated oils like LA and LNA to high temperatures during the refining process. Canola, flaxseed and soybean oil are the highest in PUFAs

Temperature also has major effects on cell membrane fluidity
If you live in hot climate, what sort of fatty acids should you have? If you live in cold climate, what sort of fatty acids should you have? Species Body Temperature oC Ratio of sat. to unsat. fatty acids in phospholipid Arctic Sculpin 0.59 Goldfish (acclimated to 2 temps) 5 25 0.66 0.82 Desert Pupfish 34 0.99 Rat 37 1.22 Saturated fats increase LDL cholesterol (the bad kind). Draw Phospholipid with fatty acid tails on board Membrane lipid exist in a fragile liquid crystal state that can be disrupted by changes in TEMP Think of salad dressing or oil in the fridge- gets gloppy and cloudy- back at room temp- it’s clear and flowing. Depending on the fatty acid composition of the membrane it will react differently to heat. Saturated fats vs. unsaturated fats- think butter and olive oil- butter stays solid at warmer temps Double bonds (unsaturated) are kinked less stable bonding with adjacent molecules (easier to pack-in)

Cage Floor temperature
Normal Diet Diet very high in unsaturated fats Common Shingleback

Preferred Body Temp Performance So, what could this animal do if their environmental temperature shifts down? Temperature Environmental Temperature shift? Increase PUFA in diet!

Enzymes = different forms of particular enzymes with different temperature optima isozymes 4 different forms of ATPase Each with a separate thermal performance curve AYPase activity vs temperature for 4 species of lizards G = Gerrhonotus multicarinatus (pref temp 30.0) S = Sceloporus undulatus (pref temp 36.3) U = Uma notata (pref temp 37.5) D = dipsosaurus dorsalis (pref temp 38.8)

Enzymes isozymes Alligator lizard Fence lizard Desert Fringed Lizard
Desert Iguana AYPase activity vs temperature for 4 species of lizards G = Gerrhonotus multicarinatus (pref temp 30.0) S = Sceloporus undulatus (pref temp 36.3) U = Uma notata (pref temp 37.5) D = dipsosaurus dorsalis (pref temp 38.8)

Cells during protein denaturation?
Heat Shock Proteins Under High Temperatures, Proteins unfold (denature) How can you protect Cells during protein denaturation?

“Heat Shock Proteins” protect against heat damage
= proteins synthesized in response to cellular stress (including high temps) function as “molecular chaperones” Heat increases Protein denatures from Heat HSP expression increases (more HSP) HSP binds up denatured protein Play a role in ‘thermotolerance’ and thermoprotection Fruit flies die at 40C But if mild heat shock is given (35C) then up to 50 % of animals live at 40C Heat decreases HSP lets go, protein can refold

Cataglyphis Ants >50C on sand 45C in nest entrance
Cataglyphis spend minutes In the tunnel to the nest, making heat shock proteins to protect their cells while they are out on the desert foraging Lives in the Sahara Desert One of the most heat tolerant animals on earth Can forage in temps up to 55C (131F) Makes heat shock proteins up to 49C (120) Fruit flies die at 40C But if mild heat shock is given (35C) then up to 50 % of animals live at 40C Other insects stop foraging <30C inside nest

Temperature Acclimatization
Biochemical Membrane dynamics Colder? Incoporate more PUFA Hotter? Use less PUFA Enzyme types and concentrations Colder or hotter? Change isozyme Goldfish Swimming Speed

Temperature Acclimatization
Biochemical Membrane dynamics Colder? Incoporate more PUFA Hotter? Use less PUFA Enzyme types and concentrations Colder or hotter? Change isozyme Heat Shock Proteins Protect protein denaturation from killing cells

Conduction Convection Radiation Evaporation Thermal Strategies Endotherm vs Ectotherm Homeothermy vs Poikilothermy Thermal Tolerance Acclimatization of membranes and enzymes

Temperature Outline Definitions: Extreme Temperature: COLD
Heat Transfer Physiological strategy: endo, ecto, etc. Temperature tolerance Extreme Temperature: COLD Death? Avoidance strategies Tolerance strategies Extreme Temperature: HEAT

COLD What causes death? Avoidance Strategies Tolerance Strategies

What causes cold death? Intracellular ice formation
- 0.5o C terrestrial, -1.7o C marine Chemical reaction rates drop CNS control, integration reduced

COLD What causes death? Avoidance Strategies Tolerance Strategies
Intracellular ice Low enzymatic reactions CNS control Avoidance Strategies Tolerance Strategies

Avoidance Hibernation/torpor
Ground hog (wood chuck)—can hibernate for a short period of time, or over months (distributed from North Carolina up the East Coast

Avoidance Hibernation/torpor Significantly lowered Tb Body Temperature
Time of day Daytime temp Ground hog (wood chuck)—can hibernate for a short period of time, or over months (distributed from North Carolina up the East Coast

Intracellular ice Low enzymatic reactions CNS control Avoidance Strategies Hibernation/Torpor/Estivation Tolerance Strategies Behavioral Physiological Extreme Cold adaptations

Tolerance Strategies: 1 (behavioral)
Change conduction, convection, evaporation and radiation Ptiloerection or piloerection (feathers and fur)

Countercurrent heat exchangers
Tolerance Strategies: 2 (physiological) Countercurrent heat exchangers also help keep animals warm… Countercurrent can be used to retain heat…

Or countercurrent can be bypassed to lose heat

But what happens below 0OC? occasional pulses of blood to feet prevent tissue damage

Tolerance Strategies: 2 (physiological)
Shivering Thermogenesis Shivering keep body temp elevated 5oC nearly 9X increase in MR! • warm up flight muscles

Oxidation of BAT produces heat, but not ATP
Tolerance Strategies: 2 (physiological) Non-shivering thermogenesis (mammals) BAT = Brown adipose tissue Oxidation of BAT produces heat, but not ATP - highly vascularized - abundant mitochondria • neonatal animals • some cold acclimated mammals • hibernators during arousal

Intracellular ice Low enzymatic reactions CNS control Avoidance Strategies Hibernation/Torpor/Estivation Tolerance Strategies Behavioral: alter heat transfer properties Conduction, convection, radiation Physiological Counter-current exchange Shivering thermogenesis Non-shivering thermogenesis Extreme Cold adaptations

Extreme Cold! (ectotherms)
Avoid Freezing Tolerate Freezing

How do some ectotherms deal with extreme cold?
Avoid Freezing Option 1: use antifreeze compounds colligative antifreezes = lower freezing point by colligative properties e.g., glycerol, sorbitol, mannitol Freezing Point Depression in Solutions (colligative) The freezing point of pure water is 0°C, but that melting point can be depressed by the adding of a solvent such as a salt. The use of ordinary salt (sodium chloride, NaCl) on icy roads in the winter helps to melt the ice from the roads by lowering the melting point of the ice. A solution typically has a measurably lower melting point than the pure solvent. Non-colligative antifreezes = lower freezing point b/c of special chemical properties

Non-colligative antifreezes:
Glycoprotein - polar groups; bind to ice crystals & prevent their growth (lowers the temp at which ice crystals enlarge)

Non-colligative antifreezes:
expression of genes for antifreeze protein increase seasonally… …and freezing point decreases seasonally in winter flounder.

Avoid Freezing Option 1: use antifreeze compounds Option 2: supercooling* -with gradual cooling, a liquid may remain unfrozen well below its freezing point… -…in the absence of ice nucleating agents * Lowers the temperature at which ice crystals form

Avoid Freezing Tolerate Freezing Option 3: promote extracellular ice formation… Option 1: use antifreeze compounds Option 2: supercooling

Promoting extracellular ice formation
animals must remain inactive ice formation is restricted to extracellular fluid Water drawn from cell Ice nucleating agents promote freezing As ECF freezes… (65% frozen) (70% frozen) (50% frozen)

Wood Frog: Freeze Tolerant
Becoming Frozen: Unfreezing: Liver freezes last—it produces glucose to keep cells from freezing (colligative antifreeze) Dark areas are frozen Why? Freeze from outside in Thaw evenly

Intracellular ice Low enzymatic reactions CNS control Avoidance Strategies Hibernation/Torpor/Estivation Tolerance Strategies Behavioral: alter heat transfer properties Conduction, convection, radiation Physiological Counter-current exchange Shivering thermogenesis Non-shivering thermogenesis Extreme Cold adaptations Freeze avoidance: antifreezes (colligative and non-colligative) Freeze Tolerance: promote extracellular ice formation

Heat Transfer Physiological strategy: endo, ecto, etc. Temperature tolerance Extreme Temperature: COLD Death? Avoidance strategies Tolerance strategies Extreme Temperature: HEAT

HEAT What causes death? Avoidance Strategies Tolerance Strategies

What ultimately causes heat death?
Disruption of membrane integrity Exceeding optimal temp for enzyme function Acetylcholinesterase temperature optima vary by species

What ultimately causes heat death?
Disruption of membrane integrity Exceeding optimal temp for enzyme function Protein Denaturation

HEAT What causes death? Avoidance Strategies Tolerance Strategies
Membrane disruption Enzyme function Protein denaturation Avoidance Strategies Tolerance Strategies

Estivation = ‘summer sleep’
Avoidance Strategies Estivation = ‘summer sleep’ Metabolic rates reduced Thermal tolerance limits expanded Growth and reproduction cease Animal becomes relatively unresponsive to external stimuli Migration Spend part of the year in different location

Alter Heat Transfer Properties
Tolerance Strategies: 1 (behavioral) Alter Heat Transfer Properties Decrease conduction from warm surfaces Increase Convection Increase Evaporation Decrease Radiation Intake

Locate appropriate microclimate
Tolerance Strategies: 1 (behavioral) Locate appropriate microclimate High evaporation Burrowing Burrows provide cooler temperatures and higher humidity FIND SHADE!

Change Effective Surface Area
Tolerance Strategies: 1 Change Foraging strategy ants Change Color Change Effective Surface Area

Vasodilation -promotes heat loss

Vasodilation Evaporative heat loss Even cicadas “sweat”! accelerated water loss for evaporative cooling at 41o C replenish with plant juices

Without rest, this rabbit will die of heat exhaustion, but the dog can keep on running… HOW?

Rete mirabile Countercurrent heat exchanger Heat exchange
“wonderful net” Countercurrent heat exchanger Arterial vessel Heat exchange Venous vessel

Rete mirabile “wonderful net” Evaporative cooling

Rete mirabile Who has it? ?? Cat Sheep Dog Rat • primates
• (& rabbits!)

HEAT What causes death? Avoidance Strategies Tolerance Strategies
Membrane disruption Enzyme function Protein denaturation Avoidance Strategies Estivation Migration Tolerance Strategies 1. Behavioral: Alter heat transfer properties Locate appropriate microclimate Change color Change foraging strategy Change effective surface area 2. Physiological: Vasodilation Sweating Rete mirabile

Heat Transfer Physiological strategy: endo, ecto, etc. Temperature tolerance Extreme Temperature: COLD Death? Avoidance Strategies Tolerance Strategies Extreme Temperature: HEAT

CAMELS BODY HEAT REGULATION WATER BRAIN FUNCTION
Ta (air temp) can exceed 50ºC (138 F) Normal mammalian body temp = 37ºC How do they cope???? BODY HEAT REGULATION WATER BRAIN FUNCTION

How do camels manage to live in the desert heat?
1. Thick fur: prevents heat gain How does it prevent heat gain? reflects suns rays that bring heat in Does it actually help? Schmidt-Nielsen in 1959 published a study on TWO camels: If removed fur from one, how much body water did they lose through evaporative heat loss?

Thick fur: prevents heat gain Body Heat can increase above 37ºC Body temp can increase to 41ºC (106ºF) Heat can be lost at night, don’t need to lose water through evaporative cooling Saves 5 L of water a day Lowers temp difference between air and camel Why would this help?

Thick fur: prevents heat gain Body Heat can increase above 37ºC Fat stored in Hump, not under skin Why Helpful??? Why would this help? During cool nights, heat loss is not restricted

Ta (air temp) can exceed 50ºC (138 F) Normal mammalian body temp = 37ºC How do they cope???? BODY HEAT REGULATION Thick Fur Body Heat to 41ºC Fat stored in hump WATER BRAIN FUNCTION

Can go for 3-4 days without water When they reach water, they can drink up to 100L in 10 minutes How does it prevent heat gain? reflects suns rays that bring heat in Does it actually help? Schmidt-Nielsen in 1959 published a study on TWO camels: If removed fur from one, how much body water did they lose through evaporative heat loss?

Can go for 3-4 days without water Minimize water loss… Concentrate Urine Camel does not sweat (until body temp above 41) The NOSE: Main place for evaporative cooling Our nasal passages 10 cm2 Camel Nasal Passages 1000 cm2 Called ‘nasal turbinate’ Can open and close to save water Nasal Membranes are HYGROSCOPIC (very cool) Urine: Humans can concentrate urine 4X (300 to 1200) camels can concentrate (9X) (300 to 2800) HYGROSCOPIC take your time explaining What is % humidity of desert air? (0%) What is % humidity of air we breathe out? (100%) So, we lose air with every breath out The camel has 1000 cm 2 of nasal passages, and those nasal membranes can attract water molecules from the air, collect back from breath (paper back book example…when outer cover is laminated, it won’t attract moisture, but inner cover does…so it bends outward) In animals, this is EXTREMELY rare in vertebrates, more common in a few insects

Ta (air temp) can exceed 50ºC (138 F) Normal mammalian body temp = 37ºC How do they cope???? BODY HEAT REGULATION Thick Fur Body Heat to 41ºC Fat stored in hump WATER Can go 3-4 days without water Concentrate urine 9-fold over plasma Doesn’t sweat (mostly) THE NOSE Huge surface area—used for evaporative cooling Can close nostrils to save water HYGROSCOPIC BRAIN FUNCTION

Body Temp can increase 6C… But Brain can’t function at that temp …? THEY KEEP THEIR BRAIN COOL! Rete mirabile “wonderful net” = Counter Current Exchange Arterial vessel Heat exchange Venous vessel

Rete mirabile “wonderful net” Evaporative cooling

Rete mirabile • brain temperature remains lower

Ta (air temp) can exceed 50ºC (138 F) Normal mammalian body temp = 37ºC How do they cope???? BODY HEAT REGULATION Thick Fur Body Heat to 41ºC Fat stored in hump WATER Can go 3-4 days without water Concentrate urine 9-fold over plasma Doesn’t sweat (mostly) THE NOSE Huge surface area—used for evaporative cooling Can close nostrils to save water HYGROSCOPIC BRAIN FUNCTION Rete Mirabile Allows for brain cooling in spite of very high body temp

Migration Routes Seasonal Animals: what environmental cues?
Photoperiod (also temp cycles, endogenous rhythms) Temperature, food availability, mate availability, nest site availability, nutritional state, rainfall All supplementary How do these cues affect migrants?

TEMPERATURE.

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