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Ecophysiology - Coggle Diagram

- - - - Metabolism is driven by redox reactions (oxidation - loss of electrons and reduction - gain of electrons), this involves electron transfers between electron donors and accepters which results in energy which is used for metabolism and the leftover energy dissipates as heat
      - Metabolic pathways form the link between organic compounds (where energy is stored) and ATP (the molecule that all cells use to deliver energy to where it's needed)
      - In aerobic respiration oxygen is the final acceptor of electrons
      - Metabolic rate is a measure of the total energy metabolised by an animal in a unit of time
      - Energy metabolised can be measured by:
        
        Amount of metabolic water produced
        
        Amount of heated product
        
        Energy value of food minus waste
        
        Amount of oxygen used up
    - - Standard Metabolic Rate (SMR)
        
        Measures the level of resting lifestyle (hard to measure as animals like to move a lot) which involves no activity, digestion or stress
        
        When measuring this for ectotherms the rate changes based on temperature
        
        When measuring this for endotherms the Basal Metabolic Rate (BMR) is measured which means it is the metabolic rate but within the animals thermal neutral zone
      - Routine/ Resting Metabolic Rate (RMR)
        
        Takes into account how hard it is to measure SMR/BMR and measures the minimal activity instead (very basic functions like circulation etc however this varies between species based on whatever we can measure)
      - Maximum Metabolic Rate (MMR)
        
        Maximum possible level during exercise
      - Field Metabolic Rate (FMR)
        
        This is the metabolic rate animals use in nature
    - - Aerobic scope is the value of how much MMR exceeds RMR (MMR-RMR), this is used to see how factors effect the survival of organisms and how much they maintain all of the functions that are necessary to keep ecological processes or if they are just existing, FMR can also be measured and plotted to see where they are in terms of functioning in nature
    - - Mass
        
        Metabolic rate isn't directly proportional to mass but it does increase with mass but it has ~75% the power (66% - 72% for inverts and 70% - 75% for birds and mammals).
        
        The metabolic rate of a gram of tissue depends on the size of the animal. Smaller animals have more metabolically active tissues. (possibly due to surface area - the smaller animal would lose heat quicker so it has to be more metabolically active to stay warm)
        
        It is better to compare the metabolic rate of animals per unit of body mass rather than just metabolic rate as it takes the size into account. (Size has to be taken into account with dosage as relying on just metabolic rate could result in overdose)
      - Temperature
        
        Endotherms
        
        Metabolic rate remains constant in the thermal neutral zones. When below the thermal neutral zone metabolic rate increases to generate heat. When above the thermal neutral zone metabolic rate also increases because thermoregulation cooling mechanisms happen. Outside of the thermal neutral zone it costs energy and oxygen.
        
        Ectotherms
        
        Metabolic rate increases with environmental temperature
        
        Q10 (temperature sensitivity)
        
        Within species (1 species multiple temperatures)
        
        Temperature sensitivity of metabolism is similar across species and highly conserved (tend to have Q10 2-3)
        
        Q10 can't be used to look at the effects temperature has on metabolism alone
        
        Between species (multiple species/ evolution and 1 temperature)
        
        Small differences in Q10 between species
        
        Why resting metabolism increases with temperature:
        
        Possible explanation 1: Temperature may directly effect RMR (Universal Temperature Dependency (UTD) hypothesis - it is physics/ thermodynamics related as temperature increases kinetic energy)
        
        Temperature affects metabolism by its rates on biochemical reactions, they are directly linked: Temperature increases, then kinetic energy increases then enzyme rate increases which increases metabolism
        
        There are limitations as some enzymes are adapted to specific temperatures and not all species live at the same temperatures so metabolic rates vary based on what they are adapted to
        
        How UTD works is summarised in an equation aka Q = b0M3/4e−E/kT Q is metabolic rate, b0 is a normalization constant independent of M and T, M is body mass, E is activation energy of metabolism, k is Boltzmanns constant and T is absolute temperature
        
        So temperature increases metabolism
        
        Possible explanation 2: Temperature indirectly effects RMR by affecting aspects of cellular physiology that increase ATP demands which are caused by higher temperatures.
        
        Involves energetic trade offs and evolutionary temperature adaptations, from looking at it from this perspective we can see the costs and benefits of the lifestyle the animal is living
      - Environmental oxygen
      - Diet/ food intake
      - Genetics
  - - - Activation energy - minimum energy required for a reaction to proceed
      - A small number of molecules have enough energy to react as they have enough energy (activation energy) (moving fast enough) to react when they collide
      - Increasing temperature increases the energy to react so there's more collusions
      - Enzymes lower activation energy meaning more molecules can react
      - Activation energy can adapt evolutionarily
    - - Increasing the temperature increases enzyme activity (enzyme and substrate interactions) until temperature levels reach higher than the optimum (~37C in mammals) where high temperature breaks weak bonds in the enzyme causing it the change shape and denature leading to reactions stopping completely
      - Michaelis-Menten constant (Km) - the ability an enzyme has to bind to its substrate (affinity)
      - Catalytic rate constant (Kcat) - Moles of substrate converted to product per moles of enzymes per second.
    - - Q10 is temperature coefficient - this is a coefficient (constant number that serves as a measure of some property or characteristic) that describes the effects of temperature or reaction rate
      - You can normally find these values on a graph where rate is on the y axis and temperature is on the x axis
        
        R1 - first reaction rate
        
        R2 - second reaction rate
        
        T1 - temperature of first reaction
        
        T2 - temperature of second reaction
      - When the reaction is not temperature sensitive the value of Q10 is 1.
      - Most enzyme reactions have Q10 values of 2-3
      - Temperature coefficient (specifically Q10) is a factor by which the rate of a reaction increases for every 10C rise in temperature
      - Physiological reactions are harder to predict
    - - Short term (hours to days)
        
        Change substrate concentration
        
        Increase energy supply for the reaction that is being catalysed
        
        Change enzyme concentration (in one case cytochrome c increases when acclimating to lower temps but increases when acclimating to higher temperatures)
        
        Alter intracellular environment (ions/ pH)
      - Mid-term (days to months)
        
        Myosin in muscle fibres can work better or worse at different temperatures due to their isoform (shape). When dealing with different temperatures animals produce different types of myosin. Acclimation to colder temperatures result in improved contractile performance of slow muscle fibres at low temperatures. Expression of myosin light chain isoforms are associated with faster-contracting fibre types. Warm acclimated fish tend to have mainly slow myosin light chains while cold acclimated fish have a lot of fast myosin light chains
      - Long term (years) / Evolution
        
        Natural selection selects amino acids (via altering genetic sequence) that promote a certain shape that gives an enzyme a certain stability at certain temperatures so organisms can evolve different enzymes to work more efficiently at different temperatures
        
        Enzymes from species with low body temperatures have higher K cat (catalytic rate constant/ enzyme efficiency) values (measure of substrate turnover rate), than warm bodied species. Km tends to be similar when at their relevant working temperatures
    - - Short term
        
        The membrane lipids of a wide range of animals vary in fatty acid composition with ambient temperature (the membranes have a mixture of saturated (makes the membrane more rigid) and unsaturated (makes the membrane more fluid as double bonds make it difficult to pack chain together as they are spread apart - this also leads to a thinner bilayer than saturated fatty acids) fatty acids. Short fatty acids are more fluid than long fatty acids, this also varies in organisms. Membrane composition is altered by diet so species may change the ratio of saturated and unsaturated fats they eat
      - Long term
        
        Homeoviscous adaptation is the adaptation of the cell membrane lipid composition to keep the adequate membrane fluidity
        
        Organisms tend to have similar fluidity values when in their typical body temperature, unless it is Antarctic species which have more solid membranes
    - - Avoidance
        
        prevent ice formation as it's lethal
        
        lower critical temperature is -5C to -20C
        
        high supercooling capacity (cooling below freezing point without solidification by having components that make it harder to freeze)
        
        supercooling point is close to lower critical temperature
        
        ice-nucleating agents are absent
        
        occurs in invertebrates and polar fish
        
        has peptide/ glycopeptide antifreezes (antifreeze proteins)
        
        Antifreeze proteins attach to ice crystal lattices preventing new water molecules adding to the ice growth
      - Tolerance
        
        Ice formation is extracellular due to extracellular ice tolerance (Ice
        Nucleating Agents - promotes ice formation)
        
        lower critical temperature of -5°C/ -70°C
        
        supercooling capacity is low
        
        supercooling point above low critical temperature
        
        has ice-nucleating agents and cryoprotectants called Polyols which are colligative (raise osmotic pressure) and membrane protectants (non-colligative- preserve membrane structure)
        
        occurs in invertebrates
        
        At low temperatures inorganic ions like calcium accumulate in the cell and enhance freezing tolerance by binding to cell membranes reducing freezing damage by stabilising the membrane against mechanical disruption caused by cell shrinkage, another way is by preventing the denaturation of membrane compounds
    - - Stress response - to maintain homeostasis and avoid macromolecular damage (macromolecular damage results in damaged proteins which cause further harm).
      - Heat shock proteins - molecular chaperones (refold heat stress damaged proteins or tag them for degradation) that are classified by weight, can be constitutive (expressed at all times) or inducible (expressed to respond to damage)
  - - - Body temperature is important because higher temperatures (usually above 40C) result in enzyme denaturation and lower temperatures (0C) tend to result in water freezing within us which results in a burst membrane
      - There is a narrow temperature range for optimal rate/ performance, animals tend to maintain their core body temperature around this value
      - Body temperature depends on the balance between internally generated heat and the heat exchanged with the enviironment
      - Poikilothermic - "cold blooded" Temperature is variable with the environment (the temperature fluctuates)
      - Homeothermic - "warm blooded" temperatures are constant with the environment (temperature stays the same(ish))
      - Ectothermic - body temperature dependent on external heat sources
        
        Ectotherms body temperature (Tb) tends to change with the ambient (environmental) temperature (Ta)
      - Endothermic - Body temperature dependent on internally generated heat (from metabolism)
        
        Endotherms body temperature (Tb) can change with the ambient temperature (Ta) however, there is a zone called the thermal neutral zone where the blood temperature of endotherms doesn't change in a range of ambient temperatures. Temperature changes tend to happen in extreme ambient temperatures resulting in hypothermia (too cold) or hyperthermia (too warm)
      - Heat is exchanged with the environment by:
        
        Convection - moving air removes radiated heat
        
        Evaporation - Loss of heat by evaporation of water
        
        Conduction - Transferred by direct contact
        
        Radiation - Emissions of electromagnetic radiation
      - Thermoregulators maintain their body temperature while thermoconformers conform to external temperatures
    - - Metabolism
        
        Heat is internally generated by metabolism
        
        Metabolism is the total of all chemical reactions in an organism, this is made up of catabolic and anabolic pathways that manage the material and energy resources of an organism
        
        Catabolism is when macromolecules are broken down to produce energy
        
        Anabolism is the synthesis of macromolecules
        
        Metabolic rate is the measure of total energy metabolised by an animal in a uni time
        
        Aerobic and anaerobic metabolism are a series of redox reactions that are done to produce ATP
        
        Aerobic metabolism has the overall equation: C6H12O6 + 38 ADP + 38 Pi + 6 O2 → 6 CO2 + 44 H20 + 38 ATP + HEAT
        
        Aerobic metabolism requires oxygen (oxygen is the final acceptor of the respiratory chain) and overall produces 32 ATP molecules
        
        Anaerobic metabolism doesn't require oxygen and produces 2 ATP molecules, for anaerobic metabolism, the final acceptor depends on what is fermented, if it is alcohol then acetaldehyde is the final acceptor, if it is lactic acid the final acceptor is pyruvate
        
        In metabolic processes some of the energy is lost as heat
    - - Categories
        
        Physiological mechanisms
        
        Retaining metabolic heat (happens in some fish)
        
        Local generation of heat - happens in snakes when incubating eggs, insects pre-flight, thermogenic plants and fish (warms brain and eyes)
        
        Full endothermy (mammals and birds)
        
        Behavioural Thermoregulation
        
        Basking - many reptiles, amphibians and insects and endotherms, regulation involves moving between sun and shade
        
        Migration - Diurnal vertical migration in the sea and lakes allows organisms to be in water at different temperatures
        
        Lifestyle restriction - happens to sessile organisms (benthic inverts + plants) and nocturnal organisms
        
        Habitat restriction - common in aquatic animals and those living in oil and sediment
      - Thermoregulation in endotherms
        
        Adjusting the rate of heat exchange between the animal and its surroundings by insulation, vasoconstriction, vasodilation and counter current heat exchange
        
        Heat loss is minimised in mammals by then being large which reduces their surface area. They are also insulated by blubber, fur or feathers
        
        Counter current heat exchanges are used to avoid het loss a the central arteries are surrounded by veins so when cold blood flows back to the core it will warm and warm blood travels to the extremities which warms the venous blood
        
        Vasoconstriction and vasodilation is used to avoid hyperthermia in endotherms
        
        Cooling by evaporation (panting and sweating)
        
        This is done in endotherms to avoid hyperthermia
        
        Behavioural responses like bathing and migrating
        
        In endotherms hyperthermia is avoided by spreading flippers to maximise surface area, flip cool sand on them and put their extremities in the water to cool down (all of these involve heat dissipation)
        
        Changing the rate if metabolic heat production by shivering and non shivering thermogenesis, this is done in endotherms when the environmental temperature is below the thermal neural zone (hypothermia)
        
        Shivering thermogenesis - An involuntary process where the nervous system senses the cold and ATP is released to fuel oscillatory contractions of antagonistic skeletal muscles (they don't require a lot of ATP), the rest is used to generate heat
        
        Non-shivering thermogenesis - This process varies between species and tissues, the heat is generated by cycling substances across membranes (one example of a tissue where this happens is brown adipose tissue and it is found in mammals, it has a lot of fat cells and mitochondria which produce ATP) the norepinephrine neurotransmitters (which stimulate aerobic metabolism by causing protons to be transferred into the mitochondria by ATP synthase) stops when heat is required and the protons travel to the mitochondria by uncoupling proteins (no ATP is involved, heat is generated by the protons)
      - Thermoregulation in ectotherms
        
        Ectotherms have low metabolic rates (lower mitochondrial densities) so they can only generate a small amount of energy which doesn't really alter their body temp that much
        
        Some ectotherms generate heat locally, they are called regional endotherms (they are still ectotherms tho)
        
        Regional endotherms
        
        Regional endotherms have the mechanisms to generate or retain heat
        
        In tuna heat is generated by swimming motions, the heat is conserved by counter-current heat exchange (subcutaneous arteries deliver blood to the red muscle and then return to the blood vessels, creating a counter current heat exchange and a strong temperature gradient across the body, which keeps heat in the core), size is also a good form of maintenance as it has a small surface area
        
        The temperature is partially independent to the water but not completely like a true endotherm
        
        In teleosts blood supply to the red muscle is carried by the central dorsal aorta and the blood returns via the central postcardinal vein
        
        Non-shivering calcium related thermogenesis happens to some ectotherms this happens in heater cells which are full of mitochondria, calcium is released through calcium channels, promoting uptake through the membrane by Ca-ATPases, using up generated ATP and producing heat as a by-product. So overall calcium is used instead of protons.
        
        This process is especially important in swordfish as it happens in its extraocular muscles which warms it's eyes and brain so it can hunt
        
        Most ectotherms can't increase heat production to maintain a specific internal temperature (their body temp is the same as the environment) so they use behavioural thermoregulation (finding an appropriate habitat (doesn't apply to sessile organisms)) or physiological regulation (not common)
        
        Fish - In teleosts body temperature tends to stay the same/close to their surroundings however, they can thermoregulate behaviourally by exploiting the water temperature or in completely cold water they can adapt to have supercooling, antifreeze proteins and high plasma NaCl cooncentrations
        
        Invertebrates - body temperature doesn't differ from ambient temperature, can thermoregulate behaviourally by picking their position on the shore, clustering/ clumping and burrowing and they can also undergo evaporative cooling
  - - - Viscosity
      - Surface tension
      - Ionisation and pH
      - Solubility of gases (O2 and CO2) and calcium carbonate
    - - As temperature effects everything, organisms are subjected to the laws of thermodynamics (energy can not be created or destroyed, only changed and transferred, every energy transfer increases the entropy of the universe, at absolute 0 entropy of a perfect crystal is 0)
        
        The flow of energy between the organism and the environment is essential to understanding how organisms function, this flow of energy is influenced by temperature
    - - Physiology definition of temperature: a measure of the mean translational kinetic energy of constituent (a part/ makes up) atoms or molecules
        
        Temperature has a direct influence on kinetic energy of molecules which effects biological processes
        
        Molecules vibrate constantly meaning they have kinetic energy, when temperature increases, vibrations increase resulting in collisions which initiates enzyme reactions which are the basis of metabolism
      - Thermodynamic definition of temperature: The property of a body that determines whether it gains or loses energy relative to its surroundings
    - - Temperature decreases with latitude higher temperature is concentrated around the equator and decreases at the poles
        
        There is more biodiversity closer to the equator, meaning that temperature is correlated with biodiversity (ps temperature doesn't influence biodiversity alone)
      - Temperature changes with time, the climate is constantly changing on a daily, weeky and seasonal basis
        
        These seasonal changes vary between continents for example in the equator and the poles the temperature doesn't change a lot however, it does vary a lot in other places
        
        Some daily temperatures also cause a lot extreme temperature changes, for example in rock pools
      - Temperature anomalies (the difference in temperature based from the reference value) of SST (sea surface temperatures) are mainly increasing. With increasing emissions SSTs will continue to rise, the more emissions, the higher the predicted temperature. If this happens extinctions will increase.
      - Organisms responses to climate change:
        
        Move - shifts their distribution
        
        Involves migration, evidence of species staying in their preferred environmental conditions and shifting species distribution, there are limits as polar species can't find anywhere colder to live
        
        Stay put
        
        Die and become locally or globally extinct
        
        Temperature can kill directly (coral bleaching) or indirectly (knock on effect after a species is killed)
        
        Cope through tolerance/ avoidance or phenotypic plasticity
        
        Cope or adapt by tolerance, avoidance, phenotypic plasticity, acclimation, adaptation over evolutionary timescales, rapid evolution through transgenerational acclimation (acclimation through generations) and epigenetics (changes in gene expression without altering DNA)
        
        Adapt through a shift in population genetic structure
    - - Variation in physiological traits is associated with the environmental variation, temperature isn't the sole dictator of this there are many other environments
      - Climate variability hypothesis - proposes that because climatic variability increases with latitude, populations and species that are at higher latitude up to temperate (the areas between tropical and polar) should have a higher thermal tolerance (a greater ability to tolerate higher and lower temperatures to cope with increased variability in the environment)
      - Thermal breadth (the difference between maximum temperature that can be tolerated and minimum temperature that can be tolerated) tends to be narrow in the polar regions as there isn't a lot of temperature variation when living in the polar regions meanwhile temperate regions have a wide thermal breadth as they experience seasonal shifts