Dr O'Quin Notes 3/21, 3/23, 3/25
Dr O'Quin Notes 3/21, 3/23, 3/25 Bio 152
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This 11 page Class Notes was uploaded by Alena Comley on Sunday April 3, 2016. The Class Notes belongs to Bio 152 at University of Kentucky taught by Dr. O'Quin in Spring 2016. Since its upload, it has received 8 views. For similar materials see Introductory Biology II in Biology at University of Kentucky.
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Date Created: 04/03/16
o Endotherms can warm themselves because their basal metabolic rates are extremely high The heat given off by the high rate of chemical reactions is enough to warm the body A high body temperature in endotherms -ability to be active in winter and at night, as well as high levels of aerobic activities such as running or flying These abilities come at a cost- endotherms have to obtain large quantities of energy-rich food Blue whales eat 3.6 tons of krill per day to fuel high metabolic rates o Ectotherms obtain the majority of their heat via radiation and conduction Have lower metabolic rate and are able to thrive with much lower intakes of food The downside to this is that chemical reaction rates are temperature dependent, so muscle activity and digestion slow dramatically as the body temperature of an ectotherm drops CLICKER #1 What is a tradeoff to being an ectotherm? A You can be active at night but have to eat lots of energy rich food. B You do better when food is scare, but metabolic rates change with environmental temperature. C You produce your own heat, but have to be really active to do so. Answer: B o Endotherms that live in aquatic environments have to deal with heat loss in unique ways Some have dense, water-repellant fur, while others have thick layers of fatty blubber One unique example is the countercurrent heat exchanger in Gray Whale tongues, which get exposed to cold water while feeding Arteries, which carry warm oxygenated blood from the body, are encircled by smaller veins, which transport cool blood back to the body core The blood vessels are arranged in an antiparallel fashion, a countercurrent exchanger, that allows for minimal heat loss in an extremity CLICKER #2 What is the benefit of a counter current exchanger? A It helps to maximize heat loss to the environment. B It allows the temperature near the body core to be less than the extremity. C It allows venous blood to be as cold near the abdomen as it is near the feet. D It minimizes temperature loss between the blood vessels so that warm blood returns to the body core. Answer: o Osmoregulation The chemical reactions of life occur in an aqueous solution composed of water and dissolved substances If the balance is disturbed, these chemical reactions and life itself may stop Water balance is associated with sustaining a balanced concentration of electrolytes-compounds that dissociate into ions when dissolved in water Cells require precise concentrations of these electrolytes to function normally Electrolytes and water move by two processes: Diffusion Osmosis Osmolarity- the concentration of dissolved substances in a solution Osmotic stress occurs when the concentration of dissolved substances is abnormal Many organisms respond to osmotic stress by controlling the concentration of water and electrolytes in their body- Osmoregulation Not all animals need to osmoregulate-these animals are osmoconformers Sponges, jellyfish, and flatworms have normal electrolyte concentrations that match the fairly constant ionic and osmotic environment of seawater Seawater is isosmotic with respect to tissue in these species (solute concentrations inside and outside these animals are equal) In contrast, marine invertebrates, marine bony fishes are osmoregulators Actively regulate osmolarity inside their bodies to achieve homeostasis o Marine Fishes o Marine fishes are surrounded by a hyperosmotic solution (solution inside the body contains fewer solutes than outside the body o The gills are involved in gas exchange and are in direct contact with the seawater o The seawater has a higher osmolarity than the gill tissue, thus water flows out of the tissue by osmosis and into the seawater o If the lost water is not replaced, the cells will shrivel and die Marine fishes replace the lost water by drinking large quantities of seawater However, this brings in excess electrolytes o Even more electrolytes diffuse into the gill epithelium following a concentration gradient from seawater to tissues o To rid themselves of these excess electrolytes, marine fishes have to actively pump ions out of their bodies and back into seawater using membrane proteins in the gill epithelium o Freshwater fishes o Freshwater fish face a different challenge- they are in constant contact with a hyposmotic solution o Freshwater fish gain water via osmosis across the gill epithelium o To achieve homeostasis, freshwater fish excrete large amounts of water in their urine and do not drink o They also lose ions and solutes to the environment, which requires them to replace them by active transport a o Terrestrial Animals o Terrestrial animals lose water via evaporation, urine, and in some species, sweating o They gain water by drinking and eating, and electrolytes are restored from the food they eat o Ammonia Waste o Animals produce ammonia as a result of the breakdown of excess amino acids and nucleic acids o Ammonia is toxic to cells, so how do organisms get rid of it safely and efficiently? Freshwater fish-->dilute in watery urine Freshwater and marine fish-->diffusion across gills Mammals & adult amphibians-->convert to urea and excrete in urine Terrestrial arthropods, birds, & reptiles--> convert to uric acid (white paste) o The type of waste excreted is actually related to evolutionary history and habitat Terrestrial birds excrete uric acid white aquatic birds excrete a combination of uric acid and ammonia Tadpoles are aquatic and excrete ammonia Frogs and toads are terrestrial and excrete urea Reptiles that live in dry habitats produce urea and uric acid CLICKER #3 If an organism lives in an aquatic environment, which type of waste will they likely produce? A Ammonia B Urea C Uric acid Answer: A There are trade-offs to the different methods of urine productions Ammonia--> larger water loss but little energy expenditure Uric acid--> little water loss but high energy expenditure Osmotic Systems Remember that marine bony fishes are osmoregulators Cartilaginous fishes, such as sharks, utilize a different approach- they are osmoconformers (their blood osmolarity nearly matches that of seawater) Instead of keeping a high amount of ions in their blood, they have high concentrations of urea in their blood instead o This allows sharks to lose less water, but there is a trade-off: they must protect their cells from toxicity of the urea (they do this by expending energy to make proteins that do this) o Because they maintain low salt concentration in their blood, salt diffuses across the gills down a concentration gradient o Salt excretion occurs from the rectal gland and is an active process + + 1 A NA /K -ATPase pumps sodium out and potassium in 2 The movement of Na down its gradient through a cotransporter and carries Cl and K with it against their gradients - 3 Cl diffuses down its concentration gradient into the lumen of the rectal gland 4 Na moves down their electrochemical gradient into the lumen of the rectal gland (this is between the cells) Many animals dealing with salt utilize the same combination of membrane proteins found in the shark rectal gland CLICKER #2 How does a shark balance water and electrolytes living in an ocean environment? A They maintain a high concentration of urea in their blood. B They drink saltwater and import the salt into their blood. C They import ions through their gills. D They import salt through the rectal gland. ANSWER: A You might recall that freshwater fish lose electrolytes across their gill epithelium and gain them back by active transport, but how does this active transport work? Scientist focused on fish that change water environments during their life time (Sea Bass) These fish use Na /Cl /K cotransporter to help move ions either in or out of the gills, depending on the water environment In seawater, they pump in electrolytes; in freshwater, they pump out electrolytes Insects maintain water and electrolyte balance by (1) minimizing water loss from their body surface o To minimize water loss, insects are able to open and close their spiracles (openings to the respiratory system) o They also posses a waxy cuticle CLICKER #3 In what ways are insects like plants? A They both have cellulose as a major protein component. B They both have thick, waxy cuticles. C They both have openings to the outside environments they can control. D Both B and C E All of the above ANSWER: D (2) carefully regulating the amount of water and electrolytes that they excrete in their urine and feces o To maintain water and electrolyte balance, insects rely on excretory organs called Malpighian tubules and their hindgut The malpighian tubules form a filtrate from the hemolymph (blood-like fluid) in a non selective process This filtrate will then flow into the hindgut and join materials from the digestive tract If the insect is osmotically stressed, water and electrolytes are reabsorbed in the hindgut and returned to the hemolymph, leaving uric acid behind Hindgut is the location of reabsorption in insects o Main thing to take away: electrolytes are pumped into the hemolymph, which causes water to follow, thus reabsorbing both In land-dwelling vertebrates osmoregulation occurs primarily in the kidney The kidney is responsible for water and electrolyte balance, as well as excretion of nitrogenous waste The kidney is part of the urinary system, which also includes the ureters, bladder, and urethra The basic functional unit of the kidney is the nephron o The nephron is surrounded by blood vessels: blood is filtered and urine is formed o Urine formation begins in the renal corpuscle o The renal corpuscle consists of a cluster of capillaries called the glomerulus, which is surrounded by the bowman's capsule Size based filtration occurs when water and small solutes pass through the pores of the capillaries and through the pores and slits of the capsule Blocks entry of cell, proteins, etc. Blood pressure is the force that helps push the blood through this filtration process CLICKER #1 What should be able to enter Bowman’s capsule? A Fluids B Cells C Small Solutes D Both A and B E Both A and C F Both B and C G All of the above ANSWER: E o Next the filtrate enters the proximal tubule and reabsorption begins + + + This is powered by Na /K ATPase and Na cotransporters ATPase pumps sodium out. Sodium flows down the gradient and carries other molecules against gradient. Other molecules flow down their concentration gradient. Water flows + + + Na /K ATPase pumps Na back into the blood o Next is the Loop of Henle, which further absorbs water and ions in a very clever way along three distinct regions The descending loop is ONLY permeable to WATER but not solutes- water moves passively by osmosis because of what happens in the ascending limb Na and Cl moves out both passively and actively, causing a high amount of solutes in the surrounding tissue So, water is able to move passively by osmosis from the descending limb because of the high solute concentration Ascending Limb- thin and thick part The water and solutes that move out of the Loop of Henle return to the bloodstream via the vasa recta CLICKER #2 What part of the loop of Henle is permeable to water? A. Descending limb B. Ascending limb Answer: A Desert animals have long Loops of Henle to help them better absorb water o The filtrate that moves into the distal tubule is dilute and contains urea and other wastes, while having a low concentration of ions If Na levels in the blood are low, the hormone aldosterone is released and Na is reabsorbed, followed by water-- Raises blood pressure o At the collecting duct, the urine leaving it can either be dilute or concentrated based on the circumstances of hydration When someone is dehydrated, the hormone antidiuretic hormone (ADH) is released by the brain ADH triggers the insertion of aquaporins into the membrane of the collecting duct, allowing water to flow out for reabsorption --small volume of concentrated urine When a person is well hydrated, this doesn’t occur and dilute urine is produced CLICKER #3 If alcohol inhibits ADH, what does that mean for water reabsorption and urine concentration? A Water is reabsorbed and urine is concentrated. B Water is reabsorbed and urine is dilute. C Water is not reabsorbed and urine is concentrated. D Water is not reabsorbed and urine is dilute. ANSWER: D o Reptiles don’t have Loops of Henle and yet produce uric acid, which contains very little water--> How is this possible? Most reptiles actually reabsorb water via the cloaca --> where the urinary, gastrointestinal, and reproductive tracts all empty Some reptiles, such as the Gila monster, have bladders which can store water during times when water is scarce and reabsorbs there.