Chapter 13 Short Answer

How do the body fluid osmolarities of freshwater and saltwater bony fishes compare to their respective environments?

Freshwater bony fish have hyperosmotic body fluids (more concentrated) while saltwater bony fish have hypoosmotic (less concentrated) body fluids

What are the osmotic challenges for freshwater and saltwater bony fish in their respective environments, and how do they maintain the osmolarity of their body fluids in their respective environments?

Freshwater bony fish gain water lose salt, so they excrete dilute urine and absorb salt through their gills. Saltwater bony fish lose water and gain salt, so they excrete concentrated urine and expel salt through their gills

How do cartilaginous fish utilize urea to maintain their osmotic balance in saltwater habitats?

By retaining a high concentration of urea and trimethylamine oxide in tissues and fluids

How do cartilaginous fish excrete excess sodium and chloride ions?

Rectal glands and gills

What are salt glands and what types of animals have such glands?

Salt glands are specialized glands that excrete excess salt. They are found in marine birds, reptiles, and elasmobranchs

Compare and contrast ammonia, urea, and uric acid in term of relative toxicity, solubility, and metabolic cost of production.

Ammonia is the most toxic, requires the most water to excrete, and has the lowest metabolic cost. Uric acid is the least toxic, requires the least water to excrete, and has the highest metabolic cost. Urea falls in between the two.

How does relative toxicity, solubility, and metabolic cost of production of nitrogenous waste forms relate to nitrogen excretion strategies (and water balance) of ammonioteles, uricoteles, and ureaoteles?

Ammonia requires a lot of water for excretion, urea requires minimal, and uric acid requires little to none

Give examples of animals that use each nitrogen excretion strategy.

Aquatic animals excrete ammonia, mammals excrete urea, and birds excrete uric acid

Explain the processes that occur in each portion of a nephron during the production of urine.

The glomerulus forms filtrate, PCT reabsorbs essential nutrients, the loop of Henle maintains a salt concentration gradient, DCT regulates water and ion balance, the collecting duct reabsorbs water, and the renal pelvis drains into the ureter

Explain the two types of intrinsic regulation of glomerular filtration rate.

The myogenic mechanism involves smooth muscle in the afferent arteriole constricting in response to increased pressure. Tubuloglomular feedback involves the macula densa sensing flow and sodium concentration in the distal tubule