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Lecture 24. Biology 1108 Chapter 44: Control of the Internal Environment. Learning Objectives (1 of 3). Contrast Osmoregulation in salt water & fresh water fish Ectotherms and endotherms Define Homeostasis Discuss “Goose bumps”. Learning Objectives (2 of 3). Contrast:

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lecture 24

Lecture 24

Biology 1108

Chapter 44: Control of the Internal Environment

learning objectives 1 of 3
Learning Objectives (1 of 3)
  • Contrast
    • Osmoregulation in salt water & fresh water fish
    • Ectotherms and endotherms
  • Define
    • Homeostasis
  • Discuss
    • “Goose bumps”
learning objectives 2 of 3
Learning Objectives (2 of 3)
  • Contrast:
    • Ammonia excretion in fish, birds, mammals
  • Recall:
    • Maximum amount of water lost to sweat
    • Functions of liver, kidneys
    • Function of each part of the excretory system
  • Discuss:
    • Seasonal dehydration
      • Water bear survival
      • Stone Mountain fairy shrimp
learning objectives 3 of 3
Learning Objectives (3 of 3)
  • Some words to define:
    • Trehalose
  • Identify ALL urinary system parts
homeostasis
Homeostasis
  • This chapter: “Control of the Internal Environment”
  • Homeostasis = maintenance of stability
  • For today, 2 types of internal control:
    • Temperature (thermoregulation)
    • Chemical (osmoregulation)
thermoregulation
Thermoregulation
  • Maintenance of a certain body temperature
  • Two basic types of animals
    • Endotherms vs. Ectotherms
ectotherms
Ectotherms
  • Most of body heat comes from outside
  • Often must use behavior to regulate heat gain/loss
    • Reptiles bask in sun or on hot rock
    • Fish find water suitable for body temp
      • Trout prefer cold
      • Bass prefer somewhat warmer
endotherms
Endotherms
  • Most of heat comes from metabolism
  • Examples:
    • Birds
    • Mammals
    • Great white sharks
endotherms limiting heat loss
Endotherms: Limiting Heat Loss
  • Most endotherms must limit heat loss
    • Thick body fat
    • Feathers in birds
    • Fur in mammals
    • Counter current exchange
goose bumps
“Goose Bumps”
  • Each hair follicle has a tiny muscle
    • When cold, muscles raise hairs
    • Insulating air is trapped
    • Works better for furry mammals
      • We still have it as vestige of our evolutionary history
  • Birds have similar strategy
counter current heat exchange
Counter Current Heat Exchange
  • Limits heat loss through blood
  • Where is it found?
    • Great white shark
    • Penguin legs
how it works
How it works:
  • Veins and arteries close together
  • Thermal energy flows from warmer to colder
    • Outgoing blood warms incoming blood
    • Heat stays towards body’s center
endotherms cooling
Endotherms: Cooling
  • Sometimes cooling necessary
  • Increased blood flow to skin helps
    • Elephants dilate ear arteries & flap
    • Humans flush
  • Sweating causes evaporative cooling
osmoregulation
Osmoregulation
  • Control of internal chemical environment
    • Ex: Enzymes require certain pH & salinity to work properly
  • Saltwater & freshwater fish must have opposite strategies for osmoregulation!
hypotonic vs hypertonic
Hypotonic vs. Hypertonic
  • Just remember to ask, “How is the outside?”
    • If less concentrated, then environment is hypotonic (lower in salt)
    • If more concentrated, then environment is hypertonic (higher in salt)
freshwater fish ion balance
Freshwater Fish: Ion Balance
  • Constantly loses ions to hypotonic (lower salt) environment
    • Sodium Na+
    • Calcium Ca+
    • Chloride Cl-
  • To compensate:
    • Gills absorb ions from water
    • Digestive system absorbs ions from food
freshwater fish water balance
Freshwater Fish: Water Balance
  • In danger of having too much water
    • These fish must avoid drinking
    • Kidneys produce copious, dilute urine
saltwater fish ion balance
Saltwater Fish: Ion Balance
  • Fish at risk of having too many ions
  • To compensate, gills constantly expel ions
saltwater fish water balance
Saltwater Fish: Water Balance
  • Environment is hypertonic (salty)
    • Will rob fish of water
  • To compensate:
    • Saltwater fish drink lots!
    • Produce very little, but concentrated urine
question
Question:
  • Let’s say you’re dehydrated
  • Which is absorbed by your body more quickly:
    • A sports drink?
    • Plain water?
dehydration from sweating
Dehydration from Sweating
  • Body sweats to cool skin
  • Up to 2 liters per hour during heavy exercise!
      • 2% loss affects performance
      • Excess loss reduces blood flow to skin, sweating stops
        • At 5%, heat stroke can occur
seasonal dehydration
Seasonal Dehydration
  • Problematic for aquatic or moisture-requiring organisms
  • Strategies
    • Lay desiccation-resistant eggs
    • Evolve to tolerate drought
stone mountain fairy shrimp
Stone Mountain Fairy Shrimp
  • Endangered species
    • Stone Mountain, GA is only home!
    • Live in ephemeral (temporary) pools
  • All adults die when pool dries up
  • Eggs resistant to dessication
    • Can survive for years
water bears survive dehydration
Water Bears Survive Dehydration!
  • Can lose 95% of body moisture!
    • Homeostasis requirement relaxed
    • Remain inactive for decades
    • Rehydrate in minutes
  • Water bears = Phylum Tardigrada
more amazing feats
More Amazing Feats:
  • Temperature: -270°C to 150°C
  • Pressure: 6000atm = 10km under sea!
  • Pure alcohol!
  • Websites
    • Nature
    • Tardigrade Animations
dehydration in nematodes
Dehydration in Nematodes
  • Some nematodes can survive dessication
    • Normally, cell membranes would collapse, proteins would break down
    • Nematodes have special sugar (trehalose) which prevents damage
    • Trehalose used to preserve some protein-based pharmaceuticals
nitrogenous wastes
Nitrogenous Wastes
  • Proteins have many nitrogen-containing amino groups
    • In waste products, they become ammonia
      • Very toxic!
  • Body must eliminate ammonia!
eliminating ammonia
Eliminating Ammonia
  • Ammonia is chemically simple
  • Fish excrete ammonia directly through gills, directly to water
  • Terrestrial animals must convert ammonia to less toxic chemicals
terrestrial animals urea
Terrestrial Animals: Urea
  • Mammals make urea
    • Water soluble (excreted in urine)
    • Disadvantage: energy cost (more complex)
terrestrial animals uric acid
Terrestrial Animals: Uric Acid
  • Birds, reptiles make uric acid
    • Not water soluble (excreted as white paste)
    • Highest energy cost (most complex)
excretory system
Excretory System
  • We have 2 kidneys
    • Filters blood, producing urine
    • Each has 80 km of tubing!
      • Tubing has semipermeable membrane
      • Sorts waste molecules out of blood
overview of excretory system
Overview of Excretory System
  • Contrast ureter vs. urethra
    • Ureter connects kidneys to bladder
    • Urethra (with an A) connects bladder to outside (think, AHHHH!)
anatomy of the kidney
Anatomy of the Kidney
  • Contrast cortex (outer surface) vs. medulla (inner parts)
  • Note that renal pelvis collects urine
anatomy of the nephron
Anatomy of the Nephron
  • Contrast filtrate vs. urine
    • Filtrate removed from blood by Bowman’s capsule
      • Has valuable solutes, glucose
    • Urine is filtrate after refining by the rest of the nephron
      • Returns solutes, glucose to blood stream
nephron details
Nephron Details
  • Filtrate goes from glomerulus, to proximal tuble, loop of Henle, distal tubule
    • Becomes more concentrated on journey
dialysis
Dialysis
  • If kidneys fail, patient must receive blood-cleansing treatment, or death will occur
  • Dialysis machine has pump, semi-permeable tubing, dialyzing solution
    • Treatments expensive
    • Three times a week, 4-6 hours each time
liver
Liver
  • Many homeostatic functions, including:
    • Changing ammonia into urea
    • Converting alcohol & drugs into inactive wastes
    • Regulation of blood glucose levels
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