Biology Chapter 49: Osmoregulation

Uric acid excretors

-Associated with egg-laying (birds, most reptiles, insects) --its low toxicity is beneficial to the fetus and the conservation of water is as well

Earthworms' tubules are metanephridia

-Coelomic fluids are filtered into them -Necessary solutes and water are reabsorbed into the blood -Wastes are excreted through pores -Insects use Malpighian tubules (49.9)

What are the principles of operation in excretory tubules?

-Excretory organs excrete salts with nitrogenous wastes -Solutes and water filters from blood -additional solutes are secreted into the filtrate; whatever is left is secreted as urine -Earthworms use a tubular system and excrete wastes through the metanephridia -insects use malpighian tubes -Humans/ vertebrates use kidneys that have specialized tubules called nephrons. Blood plasma filters into the nephrons and plasma is processed. Urine then flows into ducts and down into the ureter. This produces hyperosmotic urine

Excreting N Wastes

-From deamination of amino acids and nucleic acids -Proteins --> amino acids --> C skeleton +NH2 Acids -gills of fish, liver -Simplest product is ammonia (NH3), very soluble but also very toxic. -Suitable for fish because if it goes through ammonia it just flushes it right out

Osmoregulation- Fresh water bony fish

-Hyperosmotic to water, so it gains water and loses salt -To compensate: Actively takes up salt, doesn't erin, excretes dilute copious urine, Much nitrogenous wastes are excreted through gills

Osmoregulation- Salt water bony fish

-Hypoosmotic to sea water, so it loses water and gains salt -To compensate : it drinks a lot to regain water, however, it does take in some salt so the gills pump it out (AT). They also secrete scant isosmotic urine (fish can't produce urine that is hyperosmotic to blood).

Osmoregulation and Water balance

-Maintaining internal osmolarity (solute concentration) that is stable and different from environment -requires energy -Usually involves specific ion regulation (Na+, Cl-, H+) -Involves water uptake/loss -Organs: Gills, kidneys, glands -Most vertebrates, terrestrial animals, fresh-water animals, and some salt-water animals *animals that live in water can have completely different osmolarities from their surroundings, so they must regulate their osmolarity *Most adult vertebrates are osmoregulators

Special adaptations for osmoregulation in terrestrial animals

-Must conserve water b/c they are not always close -Marine birds, reptiles-salt glands (nasal glands or tongue in crocodiles) -Desert frogs: conserve water by reabsorbing it from the bladder and excreting uric acid -Mammals, birds excrete hyperosmotic urine -limit to how much salt can be excreted in the urine

Osmoregulation- Cartilaginous salt water fish

-Osmoconformer but ion regulator -Retains N wastes (urea, TMAO) in blood -Gains NaCl from ocean -NaCl is secreted from the rectal gland, gills gain some but doesn't lose water b/c of urea -Urea is isosmotic to blood, excreted through gills -dont drink

Excretory organs excrete salts with N wastes

-Solutes, Water filter from blood--> filtrate -Needed solutes, much water is reabsorbed across the epithelium -Additional solutes are secreted into the filtrate -Whatever is left is secreted as urine *all animals have little excretory tubules that accommodate certain processes *certain amounts of processing in the filtrate takes place before it leaves the body, it could also have other things that need to be filtered out first (ex. glucose)

Ability to tolerate salinity varies

-Stenohaline animals- narrow tolerance, most marine, aquatic invertebrates, many types of fish -Euryhaline- wider tolerance, some shellfish living in estuaries, migrating fish *migrating fish can migrate b/w salt and freshwater so they must be able to adapt

Nitrogenous wastes in terrestrial animals

-Toxicity & H2O conservation- 2 concerns NH3--> urea is less toxic and requires less water but water is still lost. Is found in cartilaginous fish, adult amphibians, and mammals NH3---> uric acid (requires lots of energy 15 steps) is hardly toxic but insoluble in water, so it conserves water. Therefore, despite energy loss, it can be a benefit to certain animals

Vertebrates use kidneys

-With specialized tubules; nephrons- lined with many epithelial cells -Blood plasma filters into nephrons- Plasma is "processed" -Urine flows into ducts and down into pelvis to ureter *birds and mammals have nephrons that can produce hyperosmotic urine

What are examples of animals that excrete ammonia, urea and uric acid. What are advantages, disadvantages of each N waste product?

-animals that excrete ammonia and urea: cartilaginous fish, adult amphibians, and mammals -Uric acid: associated w/ egg-laying (birds, reptiles, insects) -Advantages of urea: less toxic, requires less oxygen -Disadvantage of urea: water is still slightly lost -Advantages of Uric acid: hardly toxic at all, completely insoluble in water so water is conserved -Disadvantage of uric acid: requires tons of energy (15 steps)

Close up of nephron

-blood vessels filter blood plasma into nephron -filtrate is processed in tubules- i.e. water and salts are reabsorbed into blood; urine can become hyperosmotic -Urine empties into a collecting duct from many nephrons -Excretion of salt and urea requires the elimination of water- the more salt, the more water. There is a limit to how much salt can be excreted

How do osmoconformers differ from osmoregulators?

Osmoconformers take on the same osmolarity as their environment

How are salt water sharks different from bony fish in the way they deal with salt water?

Salt water sharks are osmoconformers but ion regulators, they conform to the salt water rather then try and regulate their osmolarity. -They retain nitrogenous wastes (urea and TMAO) in the blood -also gain salt from the ocean

Osmoconformers

Same osmolarity as environment (isosmotic) -May still be ion-regulators -some marine invertebrates, salt water sharks -Ion regulation may be combined with N-waste excretion in these and in regulators

There are some birds and reptiles that eat salty food because of where they live. How do they get rid of the salts?

Through salt glands (located near the head- nasal gland, tongue in crocs) Desert frogs: conserve water by reabsorbing it from the bladder and excreting uric acid -Mammals, Birds, excrete hyperosmotic urine

What does osmoregulation refer to?

active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content.

What are problems faced by terrestrial animals, marine (salt-water) animals and fresh-water animals when it comes to osmoregulation?

salt-water: loses water but gains salt, so must drink and pump out excess salt Fresh-water: gains water but loses salt, so it doesn't drink and actively takes up salt Terrestrial animals: must conserve water because they aren't always close to a water source