Chapter 44: osmoregulation and excretion

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Osmoregulation: regulation of solute concentrations and water balance by a cell ororganism 

• Osmolarity=tonicity  • 

Isoosmotic= isotonic-same concentration of solute  • Hyper osmotic = hypertonic • Hypoosmatic=hypotonic  • 

Osmoconformer= an animal that is isoosmotic with its environment  • 

Osmoregulator= an animal that controls its internal osmolarity independent of theexternal environment

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Stenohaline: organisms that cannot tolerate substantial changes in external osmolarity

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Euryhaline: organisms that tolerate substantial changes in external osmolarity

• Most marine animals are osmoconformers • 

Most marine chordates are osmoregalators  • 

Body tissues are hypo osmotic to sea water  • Osmotic water loss through gills and other parts of body surface  • Excretion of salt ions and small amounts of water on scanty urine from

kidneys(they don't pee much because they don't want to lose water)  • Gain of water and salt ions from food and by drinking seawater  • Excretion of salt ions from gills (active transport)  

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Sharks are slightly hyper osmotic to sea water  • High levels of urea (metabolic waste) in body fluids  • Requires other chemicals to protect tissues form urea, which is toxic (trimelamine

oxide)

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All freshwater animals are osmoregalators  • Body tissues are hyper osmotic to fresh water  • Porifera have contractile vacuoles

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Cnidaria use gastrovascular cavity  • Fish: body tissues are hyper osmotic to fresh water  

• Osmotic water gain through gills and other parts of body surface  • 

Uptake of water and some ions in food  • 

Excretion of large amounts of water  

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All terrestrial animals are osmoregalators

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Arthropoda: exoskeleton, excretory system to prevent water loss  • Mollusca: shell, mucus, excretory system to reduce water loss  • Chordata: skin to prevent water loss  

Metabolic water

 

• Excretion: the disposal of nitrogen containing metabolites (molecules generated bymetabolism) and other waste products  

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Excretory system • Disposal of metabolic waste  

• Particularly nitrogen • 

Most aquatic animals convert amino groups remove ammonia  • Mammals convert amino group to urea  • Many replies convert amino group to uric acid  

Ammonia

• Toxic at low concentrations

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Flushed from body with copious water  

Urea

• Requires energy to produce

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less toxic • 

Therefore you could tolerate it at higher concentration  • Therefore it requires less water to flush it out - main advantage  

Uric acid

• Requires more energy to produce than urea does  • Relatively insoluble in water  • 

So it could be excreted as paste without water  

Sponges don't have an excretory system

Excretory process: 44.10

• Platyhelminthes have protonephridia, fig 44.11 drain fluid into the the environment.Flame bulb, constantly in motion, pushes water down to the protonephridia and out ofthe body.Pump body fluid out, claim useful molecules on the wayOrgans of osmoregulation

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Annelida have metaniphridia fig 44.12  • 

Function as the same basis as protonephridia  • Body fluid being pumped out, useful molecules are reclaimed along the way  • Hypertonic • 

Important for excretion and osmoregulation  

•  Arthropoda (insects) have malpighian tubules 44.13  • Wastes and other ions pumped out, water follows by osmosis  • 

Reabsorption of water, ions and valuable organic molecules in rectum  • Osmoregulation and excretion 

 

•  Chordates 44.14-44.15 • 

Pelvis contains urinary bladder  • 

Urine is excreted through urethra  • Kidneys 

• Collecting ducts collect fluid from nephrons and take them to renal pelvis  • As blood flows through Glomerulus it loses a lot of fluid

• Bowman's capsule collects fluid around glomerulus  • Fluid goes through proximal tubule down to the loop of henle  • Fluid then goes back up the tubule to the distale tubule and drains into the

collecting duct • The fluid that leaks out of glomerulus is mostly blood plasma, it is called a

filtrate 

Humans get their water from food, by ingested liquid and derived from metabolismKangaroo rats get their water from their metabolism and some of it from the food

Humans lose water from mostly from urine, evaporation, and fecesKangaroo rats lose water mostly from evaporation (dry environment) urine and feces