Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Index cards… But first.. Monday schedule. • 11.00 to 12.30? • 12.30 to 2.00 ? • 2.00 to 3.00? Received… Books to get here Friday (except…) Do them Do them on time UN says: 1.3 million people have already been affected by the drought in Syria Check out the news story… Check out ‘man in the cube’ on Kalam el Nass tomorrow Hormones in U.S. Beef Linked to Increased Cancer Risk “- Beef produced in the United States is heavily contaminated with natural or synthetic sex hormones, which are associated with an increased risk of reproductive and childhood cancers, warns Dr. Samuel S. Epstein, Chairman of the Cancer Prevention Coalition.” What are the interactions? Will not go over pages 40 to 47 • Since it is covered in biology introductory courses • most life processes occur within the temperature range of liquid water, 0o-100oC • few living things survive temperatures in excess of 45oC • freezing is generally harmful to cells and tissues 9 Most life processes are dependent on water in its liquid state (0-100oC). Typical upper limit for plants and animals is 45oC (some cyanobacteria survive to 75oC and some archaebacteria survive to 110oC). Good: high temp -> organisms develop quicker The bad: High temperatures: • denature proteins • accelerate chemical processes • affect properties of lipids (including membranes) 10 Temperature has consistent effects on a range of processes important to ecology and evolution (Univ of New Mexico ecologists) • Rates of metabolism • Rates of development of individuals • Productivity of ecosystems • Rates of genetic mutation • Rates of evolutionary change • Rates of species formation Temperatures rarely exceed 50 degrees C (except….) Temperatures below freezing point of water are common • On land • In small ponds which may become solid during winter So: adaptation is necessary • • Freezing disrupts life processes and ice crystals can damage delicate cell structures. Adaptations among organisms vary: • maintain internal temperature well above freezing • activate mechanisms that resist freezing • glycerol or glycoproteins lower freezing point effectively (the “antifreeze” solution) • glycoproteins can also impede the development of ice crystals, permitting “supercooling” • activate mechanisms that tolerate freezing 15 Pure water: freezes at 0 degrees C Seawater: freezes at -1.9 degrees C • Contains about 3.5% dissolved salts Another physical solution to freezing is the process of lowering the temperature of a liquid or gas below its freezing point w/o it becoming a solid Liquids can cool below the freezing point w/o ice crystals development • Ice generally forms around some object (a seed) • In a seed’s absence, pure water may cool more than 20C below its freezing point w/o freezing • Recorded to -8C in reptiles and to -18 in invertebrates • Glycoproteins in the blood impede ice formation by coating developing crystals “About a dozen species of amphibians and reptiles are known to be “freeze tolerant,” able to tolerate tissue freezing under naturalistic thermal and temporal conditions. Generally, ice formation is restricted to extracellular spaces, as intracellular freezing is not tolerated. Some species survive freezing at temperatures as low as -6°C and endure freezing episodes lasting more than a month. Fully-frozen animals, in which up to 6570% of the body fluid has become ice, appear lifeless: muscle contraction, heartbeat, and breathing have ceased. There is no flow of blood to the frozen tissues, which become depleted of oxygen and energy. Nevertheless, frozen specimens arouse after thawing and can resume normal physiological and behavioral functions within a day or two. Natural freeze tolerance is promoted by special physiological adaptations, including an accumulation of certain cryoprotective compounds, a redistribution of bulk water within the body, and an innate tolerance of cells to hypoxia and dehydration.” Link is on the ecology page on the website …under a restricted range of temperatures (but of course!) Optimum: narrow range of environmental conditions to which organism x is best suited Temperature! One such example. Put a tropical fish in cold water and it becomes sluggish and soon dies; put an Antarctic fish in temperatures warmer than -5C, and it won’t tolerate it but Many fish species from cold environments swim as actively as fish from the tropics Different temperatures result in different enzyme formation (in quantity or in qualitative difference of the enzyme itself) Rainbow trout: • Low temp in its native habitat during the winter • Higher temp in the summer Many organisms accommodate to predictable environmental changes through their ability to “tailor” various attributes to prevailing conditions: • rainbow trout are capable of producing two forms of the enzyme, acetylcholine esterase: winter form has highest substrate affinity between 0 and 10oC summer form has highest substrate affinity between 15 and 20oC 23 The heat, water, food and salt budgets of animals (including us) are coupled by diet, evaporative water loss and excretion Although few animals sweat the way that we do, all lose heat by evaporation from their respiratory surfaces When water is scarce…stay out of the sun Why then do several species of seabirds nest in full sun on bare sand, while wedgetailed shearwater builds it nests undersand? Sooty terns can tolerate a hot nesting environment Theories? • Predators? • Diets and feeding regimes • Sooty Terns feed on fish and squid – close to the nesting sites; male and female cooperation in incubation duty • Shearwaters, similar diet, but feed hundreds of km from their nesting sites • So: • Sooty terns have stomach full of water-laden food water for evaporative heat loss (remember: fish provide supply of free water) • Shearwaters plenty of fat for fast but little water (fat has less water than fresh fish) 33 (moan. groan. sigh.) Use scientific literature (what is that?) Read 1 article (no older than 2005) on issue of: impact of climate change. Summarize the article. the • Grammar. Reference. Logic. Etc. no cut and paste. Email me the summary. Present the material during Due: November 4. No late papers accepted. Why? class (5-7 min) An organism’s ability to maintain constant internal conditions in the face of a varying environment is called homeostasis: • homeostatic systems consist of sensors, effectors, and a condition maintained constant • all homeostatic systems employ negative feedback -- when the system deviates from set point, various responses are activated to return system to set point 41 42 Principal classes of regulation: • homeotherms (warm-blooded animals) - maintain relatively constant internal temperatures • poikilotherms (cold-blooded animals) - tend to conform to external temperatures some poikilotherms can regulate internal temperatures behaviorally, and are thus considered ectotherms, while homeotherms are endotherms 43 As the difference between internal and external conditions increases, the cost of maintaining constant internal conditions increases dramatically: • in homeotherms, the metabolic rate required to maintain temperature is directly proportional to the difference between ambient and internal temperatures 44 Homeotherms are limited in the extent to which they can maintain conditions different from those in their surroundings: • beyond some level of difference between ambient and internal, organism’s capacity to return internal conditions to norm is exceeded • available energy may also be limiting, because regulation requires substantial energy output 45 Some animals (and plants!) may only be homeothermic at certain times or in certain tissues… pythons maintain high temperatures when incubating eggs large fish may warm muscles or brain some moths and bees undergo pre-flight warm-up hummingbirds may reduce body temperature at night (torpor) 46 47 Oxidative metabolism releases energy. Low O2 may thus limit metabolic activity: • animals have arrived at various means of delivering O2 to tissues: tiny aquatic organisms (<2 mm) may rely on diffusive transport of O2 insects use tracheae to deliver O2 other animals have blood circulatory systems that employ proteins (e.g., hemoglobin) to bind oxygen 49 Opposing fluxes of fluids can lead to efficient transfer of heat and substances: • countercurrent circulation offsets tendency for equilibration (and stagnation) • some examples: in gills of fish, fluxes of blood and water are opposed, ensuring large O2 gradient and thus rapid flux of O2 into blood across entire gill structure similar arrangement of air and blood flow in the lungs of birds supports high rate of O2 delivery 50 Countercurrent fluxes can also assist in conservation of heat; here are two examples: • birds of cold regions conserve heat through countercurrent circulation of blood in legs warm arterial blood moves toward feet cooler venous blood returns to body core heat from arterial blood transferred to venous blood returns to core instead of being lost to environment • kangaroo rats use countercurrent process to reduce loss of moisture in exhaled air 51 52 53