Transcript Slide 1
Aspects of Marine Animal Physiology •Respiration •Gaseous Exchange •Osmoregulation Basics • Aerobic respiration: process by which almost all living organisms obtain the energy they need – Oxidation of organic molecules (glucose) – glucose + oxygen carbon dioxide + water • This is a simplified version and does not show all the intermediate rxns involved • Key: respiration converts chemical energy of glucose into a form which can be used by organisms (for muscle contraction, growth, etc) • All heterotrophic organisms obtain the organic molecules either directly or indirectly from autotrophic organisms (food chains/webs) Limits to Diffusion • Organisms need to exchange materials with their environment – Include respiratory gases (O2 and CO2), nutrients, and excretory products (waste substances produced as result of metabolism) – In relatively small and simple organisms (protozoa), exchange takes place across entire body surface – As organisms increase in size and complexity, there are specialized exchange surfaces such as lungs or gills (adapted for the exchange of materials) Surface Area to Volume Ratio • As the size of an organism increases, it’s surface area decreases in relation to its volume • Very small organisms have a relatively large surface area in relation to their volume Why Cells Aren’t Big • All organisms need to exchange substances such as food, waste, gases and heat with their surroundings. • These substances must diffuse between the organism and the surroundings. • The rate at which a substance can diffuse is given by Fick's law: • Rate of Diffusion = surface area x concentration difference distance Why Cell’s Aren’t Big Investigation • The rate of exchange of substances therefore depends on the organism's surface area that is in contact with the surroundings. • The requirements for materials depends on the volume of the organism, so the ability to meet the requirements depends on the surface area : volume ratio. • As organisms get bigger their volume and surface area both get bigger, but volume increases much more than surface area. Growing cells 1µm 2µm 3µm 4µm SA/V Ratio Demonstration 5µm Why it's REALLY Important 6µm How are surface area and volume affected by growth? Size /µm 1 2 3 4 5 6 Surface area /µm2 6 24 54 96 150 216 Volume /µm3 1 8 27 64 125 216 SA/V 6 3 2 1.5 1.2 1 Results • This means that diffusion over the surface of a large organism may be insufficient to meet it’s needs – Diffusion of respiratory gases into and out of cells would be too slow – Some larger organisms are flattened (which is an adaptation to increase their surface area) – Most complex organisms have specialized exchange surfaces (lungs and gills) Transport Systems in Large Mammals • There is an exchange of materials between organisms and their environment; there is also a need for transport of materials within – Oxygen and nutrients transported to respiring tissues, CO2 and wastes are removed – In many small organisms, transport occurs by diffusion or active transport – In larger organisms – the distances are too great and diffusion alone is too slow • Large animals have internal transport systems to ensure that substances are delivered efficiently to cells and tissues and wastes are transported away – Usually consists of blood, pumped around the body by one or more muscular hearts • Fish have a single circulatory system – Blood pumped from heart to gills; blood then flows around the rest of the body before it is returned to the heart Life in Water • Atmospheric air = 21% oxygen – Concentration of DO much lower in water • Solubility of oxygen in sea water is rather lower than fresh water (due to presence of dissolved salts in sea water) – Solubility of oxygen also decreases as the temperature increases Temperature /°C 0 [DO] in sea water at equilibrium with atm/cm3 oxygen per dm3 7.97 10 6.35 15 5.79 20 5.31 30 4.46 • Many small marine animals (cnidarians) obtain oxygen they require by diffusion across their body surface • Larger, more complex animals have a specialized gas exchange surface – Often associated with a transport system for respiratory gases etc. • Majority of aquatic animals have gills – Large SA for diffusion of respiratory gases – Highly active fish have relatively large SA compared to slower fish • Also have respiratory pigments (hemoglobin and hemocyanin) – High affinity for oxygen – Assist in the uptake of oxygen from environment • Coral polyps (Cnidaria) have no specialized gas exchange organs – Do have a large surface area – Diffusion across body wall obtains enough O2 – Gas exchange also occurs across the surface of their gastrovascular cavity Pumped Ventilation • Many bony fish maintain almost constant flow of water through gills (ie: grouper) – Achieved by pumping action of the mouth and operculum – Water is drawn into mouth as the volume of the oral cavity increases (think of using a straw) – Water is then drawn through the gills by the action of the opercular covers – they increase the volume of the opercular cavity • Results in a lower pressure than in the oral cavity Ram Ventilation • Tuna swim continuously with mouth open to maintain a constant flow of water over gills – Fish alter the degree of mouth opening during ram ventilation to keep drag to the minimum – Some species (mackerel) change from pumped to ram ventilation as their swimming speed increases to between 0.5 – 0.8 m/sec • Reduces energy cost of maintaining opercular pumping at higher swimming speed Ram Ventilation Pumped Ventilation • Many marine animals maintain a different concentration of ions in their body fluids from the surrounding sea water • As seen in the table, concentrations of ions of the two inverts are similar to those of water – [ions] in blood plasma of toadfish, eel, and salmon are much less than seawater – Useful site Concentration of Ions in Seawater Compared to the Fluids of Animals Sample [Solute]/millimoles per dm3 Na+ K+ Sea water Approx 450 10 Mussel (body fluid) 474 12 Jellyfish (body fluid) 474 10.7 Toadfish (plasma) 160 5 Eel (plasma) 177 3 Salmon (plasma) 212 3 Vertebrates vs Invertebrates • Most marine inverts are osmoconformers: the concentration of solutes in their body fluid is the same as the surrounding sea water – This means water enters and leaves equally, no overall change in water content of organisms • Marine verts with osmotic concentrations of solutes lower than that of seawater lose water by osmosis – Require mechanisms to maintain their body solute and water content Osmoregulation • Osmoregulation: process by which living organisms maintain the solute and water content in their blood and body fluids – Marine bony fish (teleosts) have an internal solute concentration approx 1/3 of sea water Osmoregulation in a Marine Bony Fish Drinking sea water Na+ and Clions secreted by gills Water lost from gills by osmosis Water and some ions lost in urine Osmoregulation • Marine bony fish drink sea water – Excess salts in water are absorbed in intestine – Sodium and chlorine ions are actively secreted by chlorine secretory cells (present in gills) – Process requires energy (provided by respiration) Osmoconformers • Most marine inverts (including mussels) are osmoconformers – Internal osmotic concentration is the same as their surroundings • Their internal concentrations of individual solutes are not necessarily the same as in sea water – Indicates they have the mechanisms to regular their internal solute concentrations Concentrations of ions in the body fluid of a mussel and sea water Concentration of ions/millimoles / kg of water Sample Na+ Mg2+ Ca2+ K+ Cl- Mussel 474 52.6 11.9 12.0 553 Sea water 478.3 54.5 10.5 10.1 558.4 Eurohaline • Organisms able to tolerate a range of salinities (such as estuarine conditions) – Shore crab Carcinus maenas is common in much of world can tolerate salinities down to 6 ppt – Species of fish which migrate from sea into fresh water (including salmon, eels) • Use different mechanisms to control [ions] in their cells in their different environments – When a salmon migrates into freshwater, the active ion transport in the gills changes direction • Stenohaline: everybody else (limited tolerance)