Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 25 Control of the Internal Environment
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Let Sleeping Bears Lie Bears do not actually hibernate but are dormant during the winter Animals have internal homeostatic mechanisms to compensate for fluctuations in the external environment –Thermoregulation: maintenance of internal temperature Endothermy: body heat derived largely from metabolism Ectothermy: heat absorbed from surroundings
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings –Excretion: Disposal of nitrogen-containing wastes –Osmoregulation: Control of gain and loss of water and solutes
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings THERMOREGULATION 25.1 Heat is gained or lost in four ways An animal exchanges heat with the environment by four physical processes –Conduction: transfer of heat between molecules of objects in direct contact –Convection: transfer of heat by movement of air or water past a surface –Radiation: emission of electromagnetic waves –Evaporation: loss of heat from the surface of a liquid transforming to a gas
LE Convection Radiation Evaporation Conduction
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 25.2 Thermoregulation involves adaptations that balance heat gain and loss Each species has an optimal internal temperature range Endotherms and many ectotherms maintain a fairly constant internal temperature through five types of adaptation –Metabolic heat production Hormonal changes, movement, clustering
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings –Insulation Hair, feathers, fat –Circulatory adaptations Dilation or constriction of blood vessels Countercurrent heat exchange: warm and cold blood flow in opposite directions in adjacent vessels
LE 25-02b Blood from body core in artery Blood returning to body core in vein 35 30 20 10 99 18 27 33 C Blood from body core in artery Blood returning to body core in vein
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings –Evaporative cooling Panting, sweating, spreading saliva –Behavioral responses Migration, basking, burrowing, bathing
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 25.3 Reducing metabolic rate and body temperature saves energy Some ectotherms can spend the winter “frozen” Endotherms have various adaptations to adjust to temperature extremes –Torpor: state of reduced activity in which metabolic rate and body temperature decrease –Hibernation: long-term torpor in cold weather –Estivation: summer torpor
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings OSMOREGULATION AND EXCRETION 25.4 Osmoregulation: Animals balance the gain and loss of water and solutes Animal cells cannot survive net water gain or loss Osmoregulation is based largely on regulating solutes –Water follows the movement of solutes by osmosis
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Osmoconformers have the same internal solute concentration as seawater –Only marine animals –Expend some energy to maintain ion concentrations Osmoregulators have different solute concentration in body fluid than environment –Use energy to regulate water gain or loss –Freshwater and saltwater fishes have different adaptations –Fishes that change habitat use freshwater or saltwater strategies as necessary
LE 25-04a Uptake of some ions in food Uptake of salt by gills Excretion of large amounts of water in dilute urine from kidneys Osmotic water gain through gills and other parts of body surface
LE 25-04b Excretion of salt from gills Excretion of excess ions and small amounts of water in scanty urine from kidneys Osmotic water loss through gills and other parts of body surface Gain of water and salt from food and by drinking seawater
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Land animals are osmoregulators –Cannot exchange water directly with environment –Like marine fishes, their primary problem is losing water and becoming dehydrated Arthropods and vertebrates have adaptations that have made them the most successful land colonizers
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 25.5 Do we need to drink eight glasses of water each day? The Institute of Medicine has found that most people get sufficient water in their daily food and beverages –Men need an average of 3.8 liters daily –Women need about 2.6 liters –Caffeinated beverages do not remove water from the body Athletes or people living in hot climates may need more water
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 25.6 Animals must dispose of nitrogenous wastes Metabolism produces nitrogenous wastes from the breakdown of proteins and nucleic acids Most aquatic animals dispose of their nitrogenous wastes as ammonia –Highly soluble in water –Diffuses rapidly across cell membranes
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Land animals convert ammonia to less toxic compounds –Can be safely stored and transported in the body –Released periodically by the excretory system –Requires energy for conversion –Different adaptations and type of reproduction determine excretion as urea or uric acid
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings –Urea Excreted by mammals, most amphibians, sharks, and some bony fishes Can be stored in concentrated solution but requires water for disposal –Uric acid Excreted by birds, reptiles, insects, some amphibians Excreted as solid paste Uses more energy for excretion
LE Amino acids Nucleic acids Nitrogenous bases Mammals, amphibians, sharks, some bony fishes Most aquatic animals, including most fishes Proteins NH 2 Amino groups Birds and many other reptiles, insects, land snails Uric acid Urea Ammonia
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 25.7 The liver per forms many functions, including the production of urea The liver performs more functions than any other organ in the body –Breaks down amino acids for energy or recycling –Produces urea –Breaks down toxins –Produces bile, plasma proteins, and lipoproteins
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings –Plays a key role in regulating body metabolism Converts glucose to glycogen Balances stored glycogen and released glucose The hepatic portal vein transports nutrients absorbed by the intestines directly to the liver –Substances detoxified before going to the heart for distribution
LE Liver Intestines Kidneys Hepatic portal vein
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 25.8 Alcohol consumption can damage the liver Some breakdown products of alcohol detoxification can cause liver cell damage Heavy, frequent exposure to alcohol can produce cirrhosis, abnormal liver scarring –Impairs liver functioning –Cannot be reversed, but treatment can stop or delay progression –Also caused by hepatitis
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 25.9 The excretory system plays several major roles in homeostasis The excretory system expels wastes and regulates water and ion balance Kidneys are the main processing centers of the excretory system –Filled with tubules and intricate network of blood capillaries –Filter blood, which circulates through repeatedly
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Nephrons are the functional units of the kidneys –Extract filtrate, consisting of water, urea, and solutes, from the blood –Refine filtrate into small quantity of urine –Return most water and solutes to blood Urine leaves the kidneys via ureters –Is stored in the urinary bladder and expelled through the urethra –About 1.5 L of urine are excreted each day
LE 25-09a Aorta Inferior vena cava Ureter Urethra Urinary bladder Renal artery and vein Kidney The excretory system
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Animation: Nephron Introduction Animation: Nephron Introduction
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Overview: The key processes of the excretory system are filtration, reabsorption, secretion, and excretion Filtration –Blood pressure forces water and many small solutes into the nephron through the glomerulus Reabsorption –Valuable solutes are returned to the blood from the filtrate
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Secretion –Substances such as excess H + and toxins are transported into the filtrate Excretion –Urine, the product of the earlier processes, passes from the kidneys to the outside
LE Filtration Nephron tubule Capillary H 2 O, other small molecules ReabsorptionExcretion Urine Interstitial fluid Secretion
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings From blood to filtrate to urine: A closer look The nephron returns much of the water that filters into it from the blood –Nutrients, salt, and water are reabsorbed into capillaries from the proximal and distal tubules –Secretion of excess H +, toxins, and K + and reabsorption of HCO 3 – also occur in the tubules –High NaCl concentration in the medulla promotes reabsorption of water through the loop of Henle
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings –Final refining of the filtrate occurs in the collecting duct, where NaCl is reabsorbed –As filtrate moves through the medulla, more water is reabsorbed before the urine passes into the renal pelvis –Antidiuretic hormone (ADH) regulates the amount of water the kidneys excrete
LE Blood Bowman’s capsule Cortex Medulla Proximal tubule Nutrients H2OH2O HCO 3 NaCI HH Some drugs and poisons Loop of Henle H2OH2O NaCI HCO 3 H2OH2O HH KK NaCI Collecting duct Distal tubule H2OH2O Urea NaCI Urine (to renal pelvis) Filtrate composition H2OH2O NaCI HH HCO 3 Urea Glucose Amino acids Some drugs Reabsorption Secretion – – –
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Animation: Bowman's Capsule and Proximal Tubule Animation: Bowman's Capsule and Proximal Tubule Animation: Loop of Henle and Distal Tubule Animation: Loop of Henle and Distal Tubule Animation: Collecting Duct Animation: Collecting Duct Animation: Effect of ADH Animation: Effect of ADH
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION Kidney dialysis can be a lifesaver Failure of both kidneys will lead to death if untreated A dialysis machine is a type of artificial kidney –Blood is pumped from an artery through tubes made of selectively permeable membrane –As blood circulates, urea and excess ions diffuse out –Needed substances diffuse from the dialyzing solution into the blood