Chapter 44
Regulating the Internal
Environment
• Thermoregulation• Osmoregulation• Excretion
Homeostasis
All organisms must maintain a constant internal environment to function properly• Temperature
• pH
• ion levels
• hormones
HomeostasisHomeostasis
Body Temperature RegulationNegative Feedback
Coping with Environmental Fluctuations
Regulating:Endotherms are thermoregulatorsFundulus-osmoregulator
Conforming:EctothermsMany inverts- nonregulator
Regulators & Conformers
Spider crab Libinia
Anadromous Salmon
Heat exchange by:• Conduction- transfer of heat between objects in
direct contact with each other• Convection- heat is conducted away from an
object of high temp to low temp
- Rate varies with different materials• Radiation- transfers heat between objects not in
direct contact
- sun energy• Evaporation- change of liquid to vapor
- cooling
Four physical processes account for heat gain or loss
Heat exchange between an organism and its environment
Ectotherm vs Endotherm
Advantages of Endothermy :
• Maintains stable body temp– Cooling & heating the body
cooling and heating the body• high levels of aerobic metabolism• sustains vigorous activity for much longer than
ectotherms– Long distance running– Flight
Disadvantages of Endothermy :
Greater food consumption to meet metabolic needs
• Human metabolic mate at 200C & at rest 1,300 to 1,800 kcal per day.
• American alligator metabolic rate at 200C & at rest 60 kcal per day at 200C.
Mechanisms for thermoregulation• Insulation
- Fur- Hair- Feathers- Fat- Blubber
• Evaporative cooling- sweating, panting, bathing
• Shivering• Nonshivering thermogenesis & brown fat• Circulation adaptations
- Countercurrent exchange- Vasodilatation (cooling)- Vasoconstriction (heat conservation)
• Behavioral responses
Countercurrent heat exchangers
Goose leg Dolphin flipper
Evaporative Cooling
Hippos bathing
Brown fat- generates heat • important in neonates, small mammals in
cold environments, and animals that hibernate
• Located in neck and in inner scapula area
Non-shivering Thermogenesis• Larges amts of heat produced by oxidizing
fatty acids in the mitochondria
Brown Fat & Non-shivering Thermogenesis
Regulating Body Temp in Humans
Acclimatization to New Env. Temps.
• Endotherms (birds and mammals): grow a thicker fur coat in the winter and shedding it in the summer - and sometimes by varying the capacity for metabolic heat production seasonally.
• Ectotherms compensate for changes in body temperature through adjustments in physiology and temperature tolerance.
• For example, winter-acclimated catfish can only survive temperatures at high as 28oC, but summer-acclimated fish can survive temperatures to 36oC.
• Some ectotherms that experience subzero body temperatures protect themselves by producing “antifreeze” compounds (cryoprotectants) that prevent ice formation in the cells.– In cold climates, cryoprotectants in the body
fluids let overwintering ectotherms, such as some frogs and many arthropods and their eggs, withstand body temperatures considerably below zero.
– Cyroprotectants are also found in some Arctic and Antarctic fishes, where temperatures can drop below the freezing point of unprotected body fluids (about -0.7oC).
• Cells can often make rapid adjustments to temperature changes.– For example, marked increases in temperature
or other sources of stress induce cells grown in culture to produce stress-induced proteins, including heat-shock proteins, within minutes.
– These molecules help maintain the integrity of other proteins that would be denatured by severe heat.
– These proteins are also produced in bacteria, yeast, and plants cells, as well as other animals.
– These help prevent cell death when an organism is challenged by severe changes in the cellular environment.
• Torpor in Ground Squirrels– Body temperature: 37oC – Metabolic rate: 85 kcal per day.– During the eight months the squirrel is in
hibernation, its body temperature is only a few degrees above burrow temperature and its metabolic rate is very low.
Hibernation: long-term torpor as an adaptation to long-term winter cold and food shortage
Body Temperature and metabolism during hibernation of Belding’s ground squirrel
Osmoregulation- the control of the concentration of body fluids.
Diffusion- movement of substance from an area of greater concentration to an area of lower concentration
Osmosis- diffusion of water through a semipermeable membrane
Adaptation to Marine EnvironmentReducing salt
• Seabird and marine iguana- nasal salt secreting gland
• Sea snake- sublingual gland• Crocodile- lacrimal gland• Fish gills- chloride cells• Shark- rectal gland
Salt Excretion in Birds
Nitrogenous Waste Excretion
• Ammonia- toxic- Excrete directly into water- jellies- Detoxifyurea
• Urea- need lots of water to get rid of• Uric Acid- birds & reptiles
- more costly to produce than urea, but needs less water to be removed
Strategies to remove Nitrogenous Waste
• Osmoconformer: isoosmotic
• Osmoregulator: hyper-, hypo-,
ureoosmotic
• Euryhaline: wide tolerance range
• Stenohaline: narrow tolerance range
Balancing NaCl in Blood
Osmols- total solute concentration in moles of solute/liter of solution
Osmols- total solute concentration in moles of solute/liter of solution
Marine Fish: hypoosmotic
H2O continually leaves body
continually drinks seawater
excretes salt through gills produces small
amts of dilute urine
Less salt than external
environment
Freshwater Fish: hyperosmotic
H2O continually enters body
does not drinks water
produces large amts of dilute urine
More salt than external
environment
Shark and Coelacanth: ureoosmotic
Maintains high levels of urea and TMAO in blood
excretes salt through rectal gland
coelacanth Rana cancrivora
Hagfish: ionosmotic
nonregulator
Seawater concentration = internal concentration
Osmolarity- measure of total solutes(dissolved particles)
Ions FW m osmol/l SW m osmol/lNa+ 1 470 Cl- 1 550Ca++ variable 10 Total 10 1000
Osmolarity in Freshwater and Saltwater
Habitat Na+ Cl- Urea
seawater sw 478 558
hagfish (Myxine) sw 537 542
lamprey fw 120 96
Goldfish (Carassius) fw 115 107
Toadfish (Opsanus) sw 160
Crab-eating frog (Rana) sw 252 227 350
Dogfish sw 287 240 354
freshwater ray fw 150 149 <1
coelacanth sw 197 199 350
Adaptations to Dry Environment
• Many desert animals don’t drink water
• Kangaroo rats lose so little water that they can recover 90% of the loss from metabolic water and gain the remaining 10% in their diet of seeds.
• Also have long loop of Henle
• Most excretory systems produce a filtrate by pressure-filtering body fluids into tubules.
• Flatworms have an excretory system called protonephridia, consisting of a branching network of dead-end tubules.– The flame bulb draws water
and solutes from the interstitial fluid, through the flame bulb, and into the tubule system.
Diverse excretory systems are variations on a tubular theme
• Metanephridia consist of internal openings that collect body fluids from the coelom through a ciliated funnel, the nephrostome, and release the fluid through the nephridiopore.– Found in most annelids, each segment of a
worm has a pair of metanephridia.
• Insects and other terrestrial arthropods have organs called Malpighian tubules that remove nitrogenous wastes and also function in osmoregulation.– These open into the
digestive system and dead-end at tips that are immersed in the hemolymph.
Nephron
Hormonal Control via Negative Feedback
Hormonal Control
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