BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor CHAPTER 25 Control of the Internal Environment Modules 25.1 25.4 From PowerPoint Lectures for Biology: Concepts & Connections
Let Sleeping Bears Lie Bears don t technically hibernate They do enter a dormant state, when their body temperature drops by several degrees Bears are endotherms ( warm blooded ) Endothermic animals derive most of their body heat from metabolism (cellular respiration) Ectothermic animals warm themselves mainly by absorbing heat from their surroundings ( cold blooded )
Dormant bears have internal homeostatic mechanisms that compensate for fluctuations in the external environment Thermoregulation maintains the body temperature within a tolerable range Osmoregulation controls the gain and loss of water and dissolved solutes Excretion is the disposal of metabolic wastes
THERMOREGULATION Heat is gained or lost in four ways Body temperature regulation requires adjustment to heat gained from or lost to an animal s environment Too cold go somewhere to absorb heat energy Too hot go in shade, water or open mouth Convection Radiation Evaporation Conduction Figure 25.1
Lizard on rock Figure 25.1x
Harbor seal Figure 25.2x2
Fox in snow Figure 25.2x1
Thermoregulation depends on both heat production and heat gain or lost Both endotherms and ectotherms may change their rate of heat loss Endotherms may sleep, shed winter/spring coat/fur, feathers, put on extra insulation (fat) Humans may lose heat by sweating/perspiring (evaporative cooling)
Hormonal changes may increase heat production by raising the metabolic rate Fur and feathers help the body retain heat Shivering, as these honeybees are doing, also increases metabolic heat production Figure 25.2A
Blood flow to the skin affects heat loss, send warm blood to the skin, promotes heat loss with the environment To conserve heat move blood away from skin, constrict blood vessels Top view of shark Blood vessels of gills Skin Artery Vein Heart Capillary network within muscle Artery and vein under the skin Dorsal aorta Figure 25.2B
In a countercurrent heat exchanger, blood from the core body warms cooler blood returning from the gills or limbs Body surface (cool) 18 C 20 C Fish move blood and water in opposite directions across their gills. Blood flow 20 22 22 24 This process conserves body heat Heat transfer 24 26 Inner body (warm) Figure 25.2C
Behavior often affects body temperature Basking in the sun Sitting in the shade Bathing Burrowing or huddling Migrating Figure 25.3
Reducing the metabolic rate saves energy Torpor is a state of reduced activity and lowered metabolic rate Hibernation in cold weather (bear) Estivation in warm weather (hummingbird) Figure 25.4
Land animals gain water by drinking and eating They lose water and solutes by evaporation and waste disposal Their kidneys, behavior, and waterproof skin conserve water
Connection: Sweating can produce serious water loss Water lost in thermoregulation can cause osmoregulatory problems Drinking water is the best way to prevent dehydration during exercise Figure 25.6
Changes in water amounts inside the cells of organisms can create homeostatic challenges. Most organisms try to maintain water balance in their cell(s), called osmoregulation Many animals also remove excess metabolic wastes when they remove excess water during the process of excretion
Metabolic wastes include: Water from dehydration synthesis, eating/drinking, cellular respiration Nitrogenous wastes from protein and nucleic acid (DNA/RNA) metabolism Liver converts some amino acids into other types by taking off amino groups in a process called deamination This produces ammonia (toxic), very soluble Liver combines CO 2 and NH 3 + (ammonia) to produce urea, much less toxic and can be stored Some land animals save water by excreting a virtually dry waste called uric acid
Animals must dispose of nitrogenous wastes Different animals excrete different types of nitrogenous wastes. ALL animals eat (including protein) ALL animals produce nitrogenous wastes Type of nitrogenous waste produced and how it is excreted is determined by where they live
Proteins Nucleic acids Amino acids Nitrogenous bases NH 2 Amino groups Most aquatic animals, including many fishes Mammals, amphibians, sharks, some bony fishes Birds, insects, many reptiles, land snails Most toxic Ammonia Urea Uric acid Least toxic Figure 25.8
Fish and many other aquatic animals excrete ammonia directly into water Many land animals (mammals), sharks and some bony fish excrete urea Many birds, insects, reptiles excrete uric acid. Dry form of waste, usually white
How do organisms perform excretion? Protozoa, small, unicellular, live in water, cell membrane is excretory structure, excrete wastes directly into water.
Cnidaria (hydra, anemone, jellyfish), simple animals, 2 cell layers & hollow body cavity, live in water, each cell excrete wastes directly into water.
Earthworm (annelid), segmented worm, more complex, have tissues, organ systems and blood (closed circulatory system), each segment has a pair of filtering and excretory structures called nephridia.
Grasshopper (arthropod), exoskeleton & jointed appendages, open circulatory system, blood not always in vessels, has Malpighian tubules that absorb waste directly from blood and put into digestive system.
The excretory system plays several major roles in homeostasis The excretory system expels wastes regulates water and salt balance Kidneys filter blood remove: Urea Water (Inferior vena cava) Renal artery and vein (Aorta) Ureter Bladder Urethra Kidney Salt Forms urine altogether A. THE EXCRETORY SYSTEM Figure 25.9A
The two human kidneys each contain about 1.25 million functional units called nephrons and filter about 180 liters of filtrate (liquid filtered from blood) each day, only excrete about 1-2 liters of urine, rest (179-178 liters) is reabsorbed into the blood Urine leaves the kidneys via the ureters It is stored in the urinary bladder
Kidney has 3 functional regions: Cortex outer region: filtration Medulla middle region: concentrate urine Pelvis innermost region: collects urine and sends out of kidney Renal pelvis Ureter Renal medulla Renal cortex Bowman s capsule Renal artery Renal vein Nephron tubule Collecting duct To renal pelvis Renal cortex Renal medulla B. THE KIDNEY C. ORIENTATION OF A NEPHRON WITHIN THE KIDNEY Figure 25.9B, C
Each nephron consists of a folded tubule and associated blood vessels The nephrons extract a filtrate from the blood in a capillary ball called the Glomerulus due to the high pressure of the blood in the capillary and collect the filtrate into the Bowman s capsule They refine the filtrate into a much smaller amount of urine Bowman s capsule Arteriole from renal artery Arteriole from glomerulus Branch of renal vein 2 Loop of Henle with capillary network Glomerulus 1 Proximal tubule Capillaries 3 Distal tubule From another nephron Collecting duct D. DETAILED STRUCTURE OF A NEPHRON Figure 25.9D
Overview: The key functions of the excretory system are filtration, reabsorption, secretion, and excretion There are four steps (processes, parts) involved in urine production: Filtration: happens in the Bowman s capsule, high pressure forces liquids (water) and small solutes from the blood through the glomerulus and into the Bowman s capsule Reabsorption: nutrients and water move from the nephron tubules back into the blood capillaries, most water is reabsorbed by the Loop of Henle.
Secretion: kidney moves specific substances (nutrients, salts and water) back into the blood at the proximal tubule and leaves excess solutes in the filtrate, this forms urine Urine concentration and removal: reabsorb lots of water back into the blood, the urine is then removed from the kidney through the renal pelvis and into the ureter FILTRATION Nephron tubule REABSORPTION SECRETION EXCRETION H 2 O, other small molecules Urine Capillary Figure 25.10
Urine collected from the nephrons in the renal pelvis moves through the ureter, into the urinary bladder (muscular and elastic), bladder empties urine through the urethra and out of the body.
From blood to filtrate to urine: A closer look Antidiuretic hormone and other hormones regulate the amount of salt and water the kidneys excrete
Controlled secretion of H + and reabsorption of bicarbonate ions help regulate blood ph Secretion also includes the active transport of drugs and poisons Reabsorption of salts and urea promote the osmotic reabsorption of water
Blood Bowman s capsule Proximal tubule NaCl H 2 O HCO 3 Glucose and amino acids NaCl Distal tubule H 2 O HCO3 Filtrate H 2 O Salts (NaCl, etc.) HCO 3 CORTEX MEDULLA Some NH 3 H + drugs and poisons K + H + Collecting duct H + Urea Glucose Loop of Henle NaCl Amino acids Some drugs H 2 O NaCl Reabsorption Active transport Passive transport NaCl Urea H 2 O Secretion (active transport) Urine (to renal pelvis) Figure 25.11
25.12 Connection: Kidney dialysis can be a lifesaver A dialysis machine compensates for kidney failure It performs the function of the nephrons by removing wastes from the blood and maintaining its solute concentration
Line from artery to apparatus Pump Tubing made of a selectively permeable membrane Line from apparatus to vein Dialyzing solution Fresh dialyzing solution Used dialyzing solution (with urea and excess salts) Figure 25.12
HOMEOSTATIC FUNCTIONS OF THE LIVER The liver is vital in homeostasis It assists the kidneys by making urea from ammonia breaking down toxic chemicals (detoxifies)
Blood from the intestines flows through the liver before distribution to the rest of the body This allows the liver to adjust the blood s chemical content Liver Intestines Inferior vena cava Hepatic vein Hepatic portal vessel Figure 25.13
Skin: part of excretory system, excretes sweat (sweat gland), which is mostly water, salt and urea
Lungs: part of excretory system, excretes CO 2 and H 2 O
Disorders: Kidney failure: kidney(s) aren t working, blood is not being filtered (bad), solution is a dialysis machine (temporary) Gout: due to high protein diet, causes uric acid production and deposition in joints. Reduce protein intake and take meds to reduce uric acid production Kidney stones: based on diet (protein) and water intake