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Fundamentals of Biology Shark embryo, Squalus acanthias What does it mean to be alive?? • You may find that your definition, or view, of life differs radically from your neighbor’s. • You wouldn’t be alone there. Most scientists can’t agree on it either! • Today’s material will cover the basics of biology. What Scientists Do Agree Upon • Life uses energy for metabolism • Life maintenances itself (homeostasis). • Life grows • Life reproduces • Life reacts to changing conditions • Life finds a way!! What does it take? • If you are trying to determine what it takes to be alive what would you do? • Water would be a good starting point. • Most organisms are composed largely of water. Where to go next? • Organic molecules also play a major role in life processes. • Organic molecules are those which contain a source of carbon (except CO2 which is still considered inorganic), hydromen, and oxygen. • Most of these simple organic molecules are organized into more complex molecules such as proteins, carbohydrates, and lipids (fat). • This is done in order to manipulate energy stored within the molecules. Just imagine how much energy is stored in this whale blubber (fat). • Conversely, equal amounts of energy may be stored within the cellulose walls of this giant kelp in the form of carbohydrates (sugar). • Carbohydrates are common in the marine environment for energy and for structure. • They are also found inside and outside of animals (chitin in shells). •Other organic compounds of great importance are proteins. •Proteins consists of amino acids which contain nitrogen. • Proteins are used as building blocks for tissues such as muscles and nerves. •They are also used for hormones… …and even antifreeze! Other necessities… • In addition to proteins, carbs., and lipids, organisms rely on DNA, RNA, and ATP to transfer genes, build proteins, and store energy, respectively. • ATP is extremely important because it serves as “energy currency” for most cells. Most energy used by organisms originates from photosynthesis. • Photosynesis makes it and respiration takes it!! • Each process is essentially the reverse of the other. Photosynthesis and respiration combine to facilitate primary production. Primary producers are photosynthetic organisms for the most part. Each relys on Nitrates (NO3-1), phosphates (PO4-2), and occasionally silica (SiO2). Cells, or the basic unit of life, contain a nucleus, and various cellular organelles which carry out cell specific functions. In addition to the organelles listed certain bacteria also contain motility structures called flagella or cilia. Sometimes, all you need in life is one cell, especially if you’ve got 10,000 buddies just like yourself!! (The first labor unions???) Challenges to life! Introduction • Maintaining steady-state equilibrium in the internal environment of aquatic and marine organisms is challenging. • Much is done involuntarily (hormones, enzymes, osmoregulation, etc.) so little physical action is required, however… • “Pick-up-and-move” still an option! (Poor environment.) Definitions • Homeostasis = maintaining steady state equilibrium in the internal environment of an organisms • Solute homeostasis = maintaining equilibrium with respect to solute (ionic and neutral solutes) concentrations (i.e. salts) • Water homeostasis = maintaining equilibrium with respect to the amount of water retained in the body fluids and tissues Osmoregulation in different environments • Challenge to homeostasis depends on – Solute concentration of body fluids and tissues… – …concentration of environmental solutes • marine: ~34 ppt salinity = 1000 mosm/l • freshwater: < 3 ppt salinity = 1 - 10 mosm/l Osmoregulation in different environments • Each species has a range of environmental osmotic conditions in which it can function: – stenohaline - tolerate a narrow range of salinities in external environment – euryhaline - tolerate a wide range of salinities in external environment • short term changes: estuarine - 10 - 32 ppt, intertidal - 25 - 40 • long term changes: diadromous fishes (salmon) Four osmoregulatory strategies in fishes 1. Isosmotic (nearly isoionic, osmoconformers) 2. Isosmotic with regulation of specific ions 3. Hyperosmotic (fresh H20 fish) 4. Hyposmotic (salt H2O fish) Osmoregulation Strategies Osmoconforming (no strategy) Hagfish internal salt concentration = seawater. However, since they live IN the ocean....no regulation required! Osmoregulation Strategies Elasmobranchs (sharks, skates, rays, chimeras) – Maintain internal salt concentration ~ 1/3 seawater, make up the rest of internal salts by retaining high concentrations of urea & trimethylamine oxide (TMAO). – Bottom line…total internal osmotic concentration equal to seawater! – How is urea retained? • Gill membrane has low permeability to urea so it is retained within the fish. Because internal inorganic and organic salt concentrations mimic that of their environment, passive water influx or efflux is minimized. Osmotic regulation by marine teleosts... – – – – ionic conc. approx 1/3 of seawater drink copiously to gain water Chloride cells eliminate Na+ and Clkidneys eliminate Mg++ and SO4= advantages and disadvantages? Saltwater teleosts: active tran. passive diff. H2O drink Na+, Cl- Na+, Cl- Mg++, SO4= Na+, Cl- Mg++, SO4= chloride cells kidneys Osmotic regulation by FW teleosts – – – – – Ionic conc. Approx 1/3 of seawater Don’t drink Chloride cells fewer, work in reverse Kidneys eliminate excess water; ion loss Ammonia & bicarbonate ion exchange mechanisms advantages and disadvantages? Freshwater teleosts: active passive don’t drink H2O Na+, Cl- Na+, Cl- Ion exchange pumps; beta chloride cells water kidneys Thermoregulation in Fishes Temperature is always an issue. It affects metabolism, digestion, and reproductive behavior Fish are conformers (well, sort of...) • Body temperature is that of the environment (poikilothermic ectothermy) • Each species has particular range of temperatures that they can tolerate and that are optimal • Big difference! Behavioral Thermoregulation in Fishes • Although fish are ectotherms, they can alter their body temperature by moving to habitats with optimal temperature • Some fish can maintain body temperature greater than ambient - tunas, billfishes, relatives (nearly endothermic) Hot Fishes • Billfishes have warm brains – excess heat production from muscles around eye Size matters...when you’re small!!! Animals with high surface-to-volume ratios don’t hold heat. • “Floyd, I am soooooooo tired, how long can this go on? -Heavy Metal (80’s) • “Life moves pretty fast, if you blink you just might miss it.” -Ferris Buhler’s Day Off (90’s) Budding in coral allows multiple replications of the same entity. Since coral uses itself as a template, this is a form of asexual reproduction. Rhizomes (runners) sent from sea grass is another example of asexual reproduction. Sexual reproduction: Union of two gametes. Reproductive strategies may involve mass production of young…like this jawfish. Advantage??? or single offspring with a high degree of parental care. Next time…real animals and real names.