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4 The Chemical and Physical Environment. Notes for Marine Biology: Function, Biodiversity, Ecology By Jeffrey S. Levinton. Measures of Physiological Performance. Consider an organism that is faced with an environmental change First, it must have receptors to sense the change
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4 The Chemical and Physical Environment Notes for Marine Biology: Function, Biodiversity, Ecology By Jeffrey S. Levinton
Measures of Physiological Performance • Consider an organism that is faced with an environmental change • First, it must have receptors to sense the change • Information must be transferred to the systems that generate an adaptive response - response that improves fitness
Measures of Physiological Performance 2 • Types of adaptive response: Behavioral Physiological (cellular changes at large systemic level) Biochemical (changes of concentrations of enzymes, ions within specific cell types)
Acclimation, Regulation, and Conformance • Acclimation: Following an environmental change, organism responds, perhaps strongly, at first, but then internal state changes and organism reaches a new equilbrium - process is acclimation
Acclimation, Regulation, and Conformance 2 • Regulation: The organism maintains a constant state within the body, despite variation in the external environment
Acclimation, Regulation, and Conformance 3 • Conformance: Environmental change in the external environment might be followed by the internal state of an organism matching the environmental change
Scope for Growth 1 • Physiological condition will be reflected in resources available for growth • Greater the cost for metabolism (reactions in cells that cost energy), the less available to invest in growth and reproduction • Scope for growth are the resources available beyond the maintenance metabolism (= a positive energy balance)
Scope for Growth 2 A mussel has less scope for growth with less food and higher temperature
Mortality differences show physiological differences Rhithropanopeus harisii Neomysis americana Mortality (%) 50 % mortality line Test temperature °C Mortality test: R. harisii is more temperature tolerant than N. americana
Temperature 1 • Temperature variation is common in marine environment: Latitudinal temperature gradient can be very pronounced Seasonal temperature change common Short term changes (e.g. weather changes, tidal changes)
Temperature 2 • Temperature regulation: Homeotherms - regulate body temperature, usually higher than ambient Poikilotherms - do not regulate body temperature
Temperature 3 • Temperature regulation: Homeotherms - advantage of constancy of cellular chemical reactions, disadvantage of heat loss Poikilotherms - advantage of no cost of keeping temperature constant and high, but at the price of metabolic efficiency
Temperature 4 • Heat gain - problem for poikilotherms in intertidal zone at low tide or tidal pools on a hot day Circulation of body fluids - brings heat to surface of body so it can be dissipated Evaporation - also allows heat loss to avoid overheating
Temperature 5 • Heat loss - problem for homeotherms who maintain high body temperatures Insulation - used by many vertebrates (blubber in whales, feathers in birds) Countercurrent heat exchange - circulating venous and arterial blood in opposite directions while vessels are in contact to reduce heat loss
Temperature 6 Countercurrent heat exchange - Heating Chamber 37°C 28 °C 30 °C 32 °C 34 °C 36 °C 27°C 29 °C 31 °C 33 °C 35 °C 37 °C Example of countercurrent heat retention
Temperature 7 Countercurrent heat exchange in dolphin limb - artery is surrounded by veinlets, which return heat
Temperature 8 Poikilotherms - can compensate for temperatures by means of acclimation; can stabilize metabolic rate over a wide range of intermediate temperature Metabolic rate Stabilization of metabolism over wide range of temperature Temperature
Temperature 9 Seasonal acclimation of poikilotherms - shift from winter to summer relation of metabolic rate to temperature Winter-acclimated Metabolic rate Summer-acclimated Temperature
Temperature 10 • Evolution of temperature tolerance: Species evolve differences in temperature tolerance, e.g., Antarctic species may not be able to survive waters warmer than 10 C Populations living along a latitudinal gradient might evolve local physiological races, with different temperature responses
Temperature 11 • Freezing - a problem in winter in some habitats and in high latitudes where sea ice forms, can destroy cells as cell cytosol freezes Some fish have glycoproteins, which function as antifreeze
Temperature 12 • Heat Shock - has effects on physiological integration of biochemical reactions in cells, can denature proteins that cannot function at high temperature (unfolding of three-dimensional structure, which destroys binding with substrates)
Temperature 13 • Heat Shock 2 - heat shock proteins - are formed during heat stress, which forestall unfolding of protein 3D structure ubiquitin - low molecular weight protein that binds to degraded proteins, which are then degraded by intracellular proteolytic enzymes
Temperature 14 • Heat Shock 3 - Disruption of membranes - heat shock disrupts packing of structural phospholipids in cell membranes, which disrupts transport of ions, other cell functions
Temperature 15 • Seasonal extremes of temperature affect both activity and reproduction • Effects are different at northern and southern limits of geographic range
Temperature 16 • Survival and reproductive effects at ends of a latitudinal range of a species Winter Survival limiting Reproduction limiting Summer High latitude Low latitude
Salinity 1 • Salinity change affects organisms because of the processes of diffusion and osmosis
Salinity 2 • Osmosis - movement of pure water across a membrane permeable to water, owing to difference in total dissolved material on either side of membrane solute
Salinity 3 • Osmosis - movement of pure water across a membrane permeable to water, owing to difference in total dissolved material on either side of membrane • If salt content differs on either side of a membrane, osmotic pressure is created, water moves across in direction of higher salt content
Salinity 4 • Example of osmosis problem - animal with a certain cellular salt content is placed in water with lower salinity: water will enter animal if it is permeable - cell volume will increase, creating stress
Salinity 5 • Experiment - Place sipunculid Golfingia gouldii in diluted seawater. At first volume increases, but then worm excretes salts through nephridiopores, regulating volume back 5 0 % Body volume change 1 2 Time (hours)
Salinity 6 • Diffusion - random movement of dissolved substances across a permeable membrane; tends to equalize concentrations
Salinity 7 • Diffusion - random movement of dissolved substances across a permeable membrane; tends to equalize concentrations • Problem - diffusion makes it difficult to regulate concentration of physiologically important ions such as calcium, sodium, potassium
Salinity 8 • Most marine organisms have ionic concentrations of cell constituents similar to seawater
Salinity 9 • Organismal responses to changing salinity: Organic osmolytes (e.g., free amino acids used by invertebrates) used to counteract osmotic problems. Used to avoid using inorganic ions (e.g., Na) which are physiologically active.
Salinity 10 • Osmolytes: Free amino acids used by many invertebrates, bacteria, hagfishes. Use amino acids that have little effect on protein function (e.g., glycine, alanine, taurine) Urea used by sharks, coelacanths Glycerol, Mannitol, Sucrose used by seaweeds, unicellular algae
Salinity 11 • Bony fishes - have overall salt concentrations of body fluids of 1/3 strength of regular seawater. Creates continual osmotic problem of water loss Fish must drink continuously Gills actively secrete salts Sharks employ urea to maintain osmotic balance
Salinity 12 • Bony fishes - osmotic regulation
Oxygen 1 • Most marine organisms require oxygen for manufacture of necessary reserves of ATP, energy source in cells • Some habitats are low on oxygen - Low tide for many intertidal animals Within sediment - often anoxic pore water Oxygen minimum layers in water column - where organic matter accumulates at some depths
Oxygen 2 • Oxygen consumption increases with increasing body mass, but weight specific oxygen consumption rate declines with increasing total body mass
Oxygen 3 • Oxygen consumption is greater in animals with greater activity
Oxygen 4 • Nearly all animals are obligate aerobes, but many animals have a mix of metabolic pathways with and without use of oxygen
Oxygen 5 • Many animals use a variety of means of breaking down carbohydrates without oxygen: • Vertebrates use glycolysis - breakdown product is lactic acid, which accumulates in muscle tissue • Invertebrates have alanine and succinic acid as anaerobic breakdown products
Oxygen 6 • Oxygen uptake mechanisms: Animals only a few millimeters thick rely upon diffusion for oxygen uptake Larger animals use feathery gills with high surface area to absorb oxygen; mammals have lungs with enormous surface areas to take up oxygen Larger animals have circulatory systems that circulate oxygen to needy tissues. Many have oxygen-carrying blood pigments
Oxygen 7 • Blood pigments: substances that greatly increase blood capacity for transporting oxygen
Oxygen 8 • Blood pigments: substances that greatly increase blood capacity for transporting oxygen Hemocyanin - copper-containing protein, found in molluscs, arthropods Hemerythrin - iron-containing protein, always in cells, found in sipunculids, some polychaetes, prapulids, brachiopods Chlorocruorin - iron-containing protein, found in some polychaetes Hemoglobin - protein unit (globin) and iron-bearing unit (heme), found in many phyla(chordates, molluscs, arthorpods, annelids, nematodes, flatworms, protozoa)
Oxygen 9 • Oxygen binding of hemoglobin (Hb): Hb + O2 HbO2
Oxygen 10 • Oxygen dissociation curve showing percent of Hb in blood bound to O2 100 50 0 % saturation of Pigment by O2 0 50 100 Oxygen tension (mm Hg)
Oxygen 11 • Hb ability to hold oxygen decreases with decreasing pH - Bohr effect
Oxygen 12 • Hb ability to hold oxygen decreases with decreasing pH - Bohr effect • pH is less near capillaries that are starved for oxygen, owing to presence of CO2 released from cells - Hb drops oxygen, which diffuses into cells