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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 Acclimation, Regulation, and Conformance 4 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 Neomysis americana Rhithropanopeus harisii 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 Metabolic rate Poikilotherms - can compensate for temperatures by means of acclimation; can stabilize metabolic rate over a wide range of intermediate temperature 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 Metabolic rate Winter-acclimated 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 % Body volume change • Experiment - Place sipunculid Golfingia gouldii in diluted seawater. At first volume increases, but then worm excretes salts through nephridiopores, regulating 5 volume back 0 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 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 • Bohr effect - Oxygen 13 % pigment Saturated by O2 100 Bohr effect 50 0 0 50 100 Oxygen tension (mm Hg) % pigment Saturated by O2 Oxygen 14 • Pigment Hb binding varies with activity of species 100 Less active forms 50 More active forms 0 0 50 100 Oxygen tension (mm Hg) Oxygen 15 • Other mechanisms: Reduction of activity and oxygen uptake when oxygen is not common (e.g., at time of low tide) Light 1 • Many animals detect light with aid of a simple layer of sensory cells, but many species have complex eyes with focusing mechanisms Allows detection of prey, predators Aids in navigation • Eyes of animals: Pinhole camera Nautilus Light 2 Lens Fish Curved, reflective Scallop Light 3 • Bioluminescence - light manufactures by organisms - using specialized light organs, sometimes with the aid of symbiotic bioluminescent bacteria Functions to confuse predators Perhaps other as yet undiscovered functions The End