Life103-Week 12 and 13 Notes
Life103-Week 12 and 13 Notes Life 103
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This 9 page Class Notes was uploaded by Addy Carroll on Sunday April 24, 2016. The Class Notes belongs to Life 103 at Colorado State University taught by Dr. Dale Lockwood and Dr. Tanya Dewey in Winter 2016. Since its upload, it has received 17 views. For similar materials see Biology of organisms-animals and plants in Biology at Colorado State University.
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Date Created: 04/24/16
Life 103 Notes *Adapted from the lecture slides of Dr. Tanya Dewey* Circulation • All animals must obtain nutrients and oxygen, excrete wastes, and move • Animals live in nearly every conceivable kind of environment (temperature, pressure, salinity, oxygen concentrations, light levels, currents, selective pressures, etc.) -Exchange with the environment is ultimately at the cellular level- substances in solution travel across the plasma membrane of cells • Surface area to volume ratios -As volume increases, surface area to volume ratio decreases -Unicellular and cells in simple, multicellular organisms can exchange directly with the environment -Cells of larger, complex organisms cannot exchange directly with the environment ~It’s less efficient to directly exchange between the body and the environment across the surface, in this case ~So other surface areas are created for exchange- internal/protected huge surface areas • 3 components of a circulatory system -Circulatory fluid: carries nutrients and (possibly) oxygen and wastes -A system of vessels: for fluid transport -A pump (heart): uses metabolic energy to generate pressure to move fluids • Closed vs. Open Circulatory Systems -Open circulatory systems: the system of vessels is open/not continuous; Hemolymph is the fluid that all cells are in contact with for exchange; pressure changes and body movements and valves move fluid back into the heart (see textbook figure 42.3a) ~Found in arthropods, many molluscs, many phyla -Closed circulatory systems: the system of vessels is closed/continuous; the circulatory fluid is blood and is distinct from interstitial fluids; heart(s) pump blood through vessels, exchange is between blood and interstitial fluids and interstitial fluids and cells (see textbook figure 42.3b) -Closed circulatory systems are more metabolically costly; higher pressure means more effective delivery of oxygen to tissues ~Animals that require more energy usually have closed circulatory systems -Open circulatory systems are metabolically cheaper and have lower pressure ~Animals that require less energy usually have open circulatory systems • Closed Circulatory Systems -Arteries: carry blood away from the heart -Capillaries: capillary beds infiltrate tissues with thin, porous walled vessels; this is the site of exchange with tissues, including gases (O a2d CO 2 and chemicals (nutrients and waste products) -Veins: carry blood to the heart • Single Circulatory System (see textbook figure 42.4a) -Found in ray-finned fishes and sharks and rays -Single pump ~Single atrium: receives blood into the heart ~Single ventricle: pumps blood out of the heart -Oxygenation of blood in the gills • Double Circulatory System -In frogs and most reptiles (see textbook figure 42.4b) ~Two atria: receives blood into the heart ~Single ventricle: pumps blood out of the hears -Because there’s only one ventricle with two atria, there’s often mixing of oxygenated and deoxygenated blood, which results in a loss of efficiency ~Still a single heart=pump ~Oxygenation of blood in pulmocutaneous circuit (lungs and skin/gills) -In mammals and birds-need more efficient systems because they have higher metabolic rates (see textbook figure 42.4c) ~Two atria: receive blood into the heart ~Two ventricles: push blood out of the heart ~Oxygenation of blood in the lungs (pulmonary circuit) • Oxygenation -Blood carries oxygen via special reversible, oxygen-binding molecules (proteins) ~Needs to be reversible because it would do no good if the oxygen just stayed bonded to the protein and never was released to the tissues -Hemoglobin (vertebrates)-iron, incorporated into red blood cells ~Picks up 4 O m2lecules in high O , hi2h pH environments ~Releases O in2deoxygenated, low pH tissues via diffusion ~As the O concentration on the hemoglobin increases, the 2 saturation of the molecule increases -This relationship eventually hits a plateau because hemoglobin can only carry 4 O mo2ecules, so at that point it’s completely saturated -Hemocyanin (crustaceans, some molluscs)-copper, suspended in blood • O2and CO in 2he circulatory system -Hemoglobin has higher saturation in areas with lower CO and 2ower saturation in areas with higher CO 2 ~Hemoglobin loses affinity for oxygen in high CO env2ronments, so that’s why it can release the O m2lecules ~The capillaries have higher CO , 2o that’s why that’s the site of exchange of oxygenated and deoxygenated blood, when the O 2 goes to the rest of the body • Fluid flow through the circulatory system -The heart generates force -The atria collect blood from the lungs and the body -The ventricles force blood into the circuits -The arteries have a thick layer of smooth muscle and connective tissue to accommodate the pressure generated in the heart; they get smaller and smaller the farther away the are from the heart -The capillaries are very thin-walled in order to promote diffusion; smaller than arteries and veins -The veins have to bring the blood back to the heart without accumulating much pressure; this is accomplished by the valves which prevent pressure from building up too much; get bigger as they get closer to the heart (see textbook figure 42.9) -As the blood vessels have smaller volume the farther away they get from the heart, the surface area increases ~In other words, the surface area is the greatest at the capillaries and lowest closer to the heart at the arteries and veins -Velocity is greatest just after leaving the heart through the arteries, is the lowest at the capillaries, and then regains some velocity on the way back to the heart through the veins -Blood pressure is the highest just after leaving the heart through the arteries and continues to decrease throughout the rest of the circuit and is never regained (see textbook figure 42.10) -Opposing forces: blood pressure and osmotic pressure (see textbook figure 42.14) ~Osmotic pressure is exerted at the capillaries, while blood pressure is exerted out of the capillaries ~Osmotic pressure stays the same throughout the capillaries, but blood pressure starts off much higher than osmotic pressure and proceeds to decrease throughout -Therefore, there is a net loss of fluid from capillary beds -Lymph: responsible for collecting the fluid the body lost to the tissues and bring it back to the core of the body and eventually the heart Gas Exchange • Respiratory exchange surfaces- responsible for getting oxygen into the body and removing carbon dioxide from it; must be moist because gases cannot cross membranes except in aqueous solutions -Aquatic animals-moist membranes are not a challenge because they are already in water anyway; respiration done by gills (and other mechanisms) -Cutaneous respiration- respiration across the skin -Terrestrial animals-moist membranes are a challenge; respiration done through exchange across moist skin and the use of lungs (internal to the organisms; also have moist exchange surfaces); most diverse groups use internal exchange surfaces (lungs or tracheal system); some terrestrial animals have gills • Respiratory media (medium can be either air or water) -Gas exchange is the uptake of O fr2m the environment and discharge of CO 2 -Partial pressure: the pressure exerted by a particular gas in a mix of gases; O 2s less soluble in water, so the concentration of O i2 water is lower at the same partial pressure -Terrestrial breathing doesn’t have to be terribly efficient because the respiratory medium is not dense or viscous -Aquatic animals have to extract O v2ry efficiently because the respiratory medium is dense and viscous • Rate of Diffusion -Movement of O an2 CO acro2s membranes (respiratory surfaces) is by diffusion -Rates of diffusion increase with increasing surface area, decreasing distance, and increasing concentration gradient • Gas exchange and ventilation mechanisms -Movement of the respiratory medium across the respiratory surface is ventilation -Non-directional ventilation ~No movement of the respiratory medium ~Efficiency of exchange influenced by concentration of gases in the medium-a boundary layer can develop ~The blood flow across the organism’s exchange surface pulls oxygen from the medium -Unidirectional ventilation ~The medium moves in the same, one direction through the organism ~Example: in sharks, the water comes through the mouth, then out through the gills (diffusion of 2 and CO i2 water into blood) ~Gills: countercurrent exchange system (always refers to things flowing in opposite directions) (see textbook figure 42.22) -80% of O 2n water removed -Tidal ventilation ~Example: in humans, air moves in, air moves out ~Lungs: diffusion of O and CO in air into blood 2 2 ~Not very efficient in oxygen diffusion; the air coming in mixes with the deoxygenated air that was already there -Unidirectional ventilation in bird lungs (see textbook figure 42.26) ~Flying is very metabolically expensive, so they’ve developed unidirectional ventilation in order to increase efficiency of oxygen diffusion in lungs; this is possible because there is no mixing of air, like in tidal ventilation, and there are two cycles of inhalation and exhalation -Elephant seals- extraordinary adaptations for gas exchange in diving ~Spend 10 months foraging in deep ocean water and 2 months fasting on land, where they lose 1/3 of their body weight ~Blubber to retain heat and neutral buoyancy-efficient in cold water ~Extreme sexual dimorphism ~Dive up to 2 hours at a time at depths up to a mile (only sperm whales go deeper) ~Ventilate at surface for just a few minutes between dives ~Allow lungs to collapse to avoid decompression illness ~Store oxygen in massive blood volume and myoglobin in muscles Osmoregulation • Review diffusion and osmosis -Diffusion: the net movement of a substance from a region of high concentration to a region of low concentration; the movement of a substance down a concentration gradient ~Occurs with or without a membrane, however in most biological process, a membrane is involved -Example: O ,2CO , 2nd H O 2iffuse readily across plasma membranes -Osmosis: spontaneous (no energy required) net movement of solvent molecules through a semi-permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides (see textbook figure 44.2) ~Requires a semi-permeable membrane ~In biological systems, the solvent is typically water -Movement of O a2d CO acr2ss membranes is by diffusion -Rates of diffusion increase with increasing surface area, decreasing distance, and increasing concentration gradient -Hypertonic: having a higher osmotic pressure as compared to a fluid -Isotonic: having the same osmotic pressure compared to a fluid -Hypotonic: having lower osmotic pressure as compared to a fluid -Hyperosmotic: having a higher solute concentration that another solution -Isosmotic: having the same solute concentration as another solution -Hypoosmotic: having a lower solute concentration than another solution -Tonicity is all relative • Osmoconformers vs. Osmoregulators -Osmoconformers: marine invertebrates and some vertebrates; isosmotic with their environment (same solute concentration), but differ in the specific solutes in their tissues (ionoregulators) -Osmoregulators: everything that isn’t an osmoconformer; expend energy to control water uptake or loss in a hyperosmotic or hypoosmotic environment • Marine, freshwater, and terrestrial osmoregulation -Osmoregulation in fish: challenge depends on the osmolarity of the environment (see textbook figure 44.4) ~Marine fish are hypoosmotic to marine water and they must expend energy to avoid water loss ~Freshwater fish are hyperosmotic to freshwater and they must expend energy to lost water and avoid solute loss -Terrestrial animals: challenge is desiccation ~Have body coverings to specifically prevent water loss ~Use physiological and behavioral mechanisms to avoid water loss -Example: Nocturnality; it’s cooler at night, causing less heat stress, thereby decreasing water loss ~Gain water through cellular respiration ~Water gain -Ingestion of water present in food -Drinking free water -Metabolic production (cellular respiration) ~Water loss -Gas exchange: lose water through moist epithelia; exhalation and water loss across skin -Urination and defecation: losing nitrogenous wastes -Camels ~Minimize water loss from moist epithelia (nasal turbinals, etc.) -Turbinals: During inhalation, the air is warmed when passed by warm tissue, the warm air picks up moisture from turbinates, and the tissue is cooled as heat is transferred; during exhalation, the air is cooled as it passed cool tissue and water is lost to turbinates ~Fat storage: metabolism of fat produces more water than metabolism of proteins or sugars ~Rapidly re-hydrate (can drink 200 liters of water in minutes) ~Withstand dehydration (oval red blood cells) ~Highly concentrated urine and feces -Elephant seals-osmoregulatory challenges ~Marine mammals-little to no access to freshwater ~Spend months fasting; females lactate during this time -Water in-fat metabolism -Water out-lactation, gas exchange, defecation and urination • Transport epithelia-counter current exchanges -To control solute content in interstitial fluids, animals expend energy to remove solutes -Transport epithelia are specialized cells for moving particular solutes in a direction (into or out of the body) -Salt glands help marine animals remove excess salts when they drink salt water • Nitrogenous wastes -Ammonia: toxic; excreted in large quantities of water; used by only animals with access to large quantities of water (freshwater species); requires little energy to generate; release across body surface or gills -Urea: limited water, so transform ammonia into urea, which has low toxicity; requires energy to generate; transported to bladder for concentration -Uric acid: limited water, transform ammonia into uric acid; low toxicity; not very soluble in water; excreted as a semi-solid paste; requires more energy to create -Waste products depends on phylogeny and habitat (availability of water) (see textbook figure 44.7) Excretion • Excretion: the process of expelling waste products • Nitrogenous wastes -Metabolism of amino acids results in nitrogenous wastes -Amino acids are amine (NH ) + carboxylic acid group (COOH) + side 2 chain (R) -Enzymes remove amino groups as ammonia (NH ) 3 -Ammonia is very toxic -Animals expend energy to convert ammonia to a less toxic compound: urea or uric acid -Urea-CO group added to amines -Uric acid-very metabolically expensive to produce; end product of purine metabolism in mammals • Excretory process (see textbook figure 44.8) -Filtration: body fluid (blood, hemolymph, or other body fluids) comes into contact with the selectively permeable membrane of a transport epithelium; hydrostatic pressure (blood pressure in mammals) drives filtration; water and small solutes (salts, sugars, amino acids, nitrogenous wastes) cross the membrane, becoming the filtrate -Reabsorption: valuable molecules actively transported back into boy fluids -Secretion: additional wastes actively transported into waste fluid -Excretion: fluid wastes removed from the body • Mammalian kidney (see textbook figure 44.12, 44.13, 44.13, -Kidneys are paired organs in vertebrates responsible for filtering wastes from blood and removing them from the body -Set of tubes (tubules) that create a large surface area for exchange of water and solutes via transport epithelia -Supplied with blood by the renal artery -Blood leaves via the renal vein -Most blood in the kidney is filtered and then reabsorbed into blood fluid -Remaining fluid leaves as urine -Filtration in glomerulus, collected in Bowman’s capsule -Reabsorption in proximal tube -Secretion in distal tubule -Excretion through duct to bladder -Tubules are arranged into nephrons, where filtration, reabsorption, and secretion occur -Capillaries of glomerulus are very porous -Filtrates collected in Bowman’s capsule contain salts, glucose, amino acids, vitamins, nitrogenous wastes, etc. at same concentrations as in blood -Proximal tubule-salts, sugars, amino acids, and ions are actively transported out of filtrate; water follows by osmosis -Other waste products actively transported into the proximal tube -Loop of Henle-descending limb -Numerous water channels make the epithelium permeable to water -Little permeability to salts and other solutes -Interstitial fluids are hyperosmotic to filtrate, so water flows through osmosis out of the filtrate -Loop of Henle-ascending limb -Transport epithelium is impermeable to water -NaCl moves out of filtrate into interstitial fluids of medulla, which maintains the concentration of solutes in the medulla -Filtrate becomes more dilute as it ascends + -Distal tubule-regulates potassium (K ) and sodium chloride (NaCl) concentration in body fluids via secretion and reabsorption -Collecting duct-water flows by osmosis out of filtrate in the collecting duct as it travels back through the medulla of the kidney -Cortical nephrons-reach only a short distance into the medulla -Juxamedullary nephrons-extend deep into the medulla and are critical for concentrating urine -An important adaptation to living in terrestrial habitats -Energy is required to transport solutes against concentration gradients -The kidneys work very hard; gallons of blood flow through them every day and 99% reabsorption occurs • Loop of Henle: a countercurrent multiplier system -Maintains a concentration gradient along the loop of Henle -Fluids run counter to each other along an osmotic gradient (concentration gradient) -Involves active transport of materials rather than only passive diffusion of heat or gases along a concentration gradient • Variation in kidneys -Reptiles, including birds, do not produce very concentrated urine because loops of Henle do not extend as far into the medulla -Freshwater fish and amphibians produce dilute urine in large quantities; frogs reabsorb fluids from bladder -Marine ray-finned fish drink large quantities of sea water; kidneys mainly + + tran+port -ivalent ions (Ca , Mg , etc.), gills transport monovalent ions (Na , Cl ); drink large quantities of sea water