Osmoregulation and Excretion

Question 1

Osmoregulation

Answer 1

Regulation of solute concentrations and balance of gains and losses of water

Question 2

Excretion

Answer 2

Getting rid of nitrogenous metabolites and other waste products

Question 3

Osmolarity

Answer 3

Solute concentration of a solution

Determines movement of water across a selectively permeable membrane

Question 4

Osmoconformers

Answer 4

Some marine animals (mostly invertebrates)

Isoosmotic with surroundings and don’t regulate their osmolarity

Question 5

Osmoregulators

Answer 5

Expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment

Question 6

Anhydrobiosis

Answer 6

Life without water

Tardigrades: organisms that can live without water for a long time

Question 7

Stenohaline

Answer 7

Animals that cannot tolerate substantial changes in external osmolarity
Humans, insects, most fish, birds, mammals

Question 8

Euryhaline

Answer 8

Animals that can survive having large fluctuations in external osmolarity
Barnacles: euryhaline osmoconformers
Salmon: euryhaline osmoregulators

Question 9

Transport epithelia

Answer 9

Epithelial cells that are specialized for moving solutes in specific directions
Typically arranged in complex tubular networks
Example: nasal glands of marine birds, which remove excess NaCl from blood (salt is secreted through nose and runs down beak)

Question 10

3 main waste products

Answer 10

Ammonia (NH3)
Urea
Uric acid

Question 11

Ammonia as waste

Answer 11

Fish
Excrete small amounts 
Need access to large amounts of water
Low metabolic cost to produce
Release this across whole body surface or through gills

Question 12

Urea as waste

Answer 12

Mammals and most adult amphibians
Circulatory system carries this to the kidneys, where it is excreted
More energetically expensive than NH3, but requires less water

Question 13

Uric acid as waste

Answer 13

Insects, land snails, many reptiles, birds
Nontoxic: doesn’t harm embryos in eggs
Isn’t readily water soluble
Can be excreted as paste with little water loss
More energetically expensive to produce than urea

Question 14

Key functions of most excretory systems

Answer 14

Filtration: filtering of body fluids
Reabsorption: reclaiming valuable solutes
Secretion: adding nonessential solutes and wastes from the body fluids to the filtrate
Excretion: processed filtrate containing nitrogenous wastes is released from body

Question 15

Protonephridia

Answer 15

Excretory system in flatworms
Network of dead-end tubules connected to external openings
Smallest branches of network are capped by cellular units called flame bulbs
Flame bulb contains cillia that direct fluid down tubules

Question 16

Metanephridia

Answer 16

Excretory system in segmented worms
Each segment has pair of these
Consist of tubules that collect coleomic fluid and produce dilute urine for excretion

Question 17

Malpighian tubules

Answer 17

Excretory system in terrestrial arthropods
Remove nitrogenous wastes from hemolymph and function in osmoregulation
Insects produce mainly uric acid: adaptation to terrestrial life

Question 18

Excretory organs of humans

Answer 18

Renal artery and vein connect to kidney

Kidney -> ureter -> urinary bladder -> urethra

Question 19

Flow of fluid through kidneys

Answer 19

Renal cortex (outermost layer) -> renal medulla (chambers between cortex and pelvis) -> renal pelvis (main chamber in middle) -> ureter (tube connecting pelvis with bladder)

Question 20

Nephron types

Answer 20

Cortical nephron: mainly in renal cortex, but a bit in renal medulla
Juxtamedullary nephron: extend from renal cortex into renal medulla

Question 21

Flow of fluid through nephron

Answer 21

Arteriole from renal artery -> Glomerulus -> Bowman’s capsule -> proximal tubule -> loop of Henle -> distal tubule -> collecting duct

Question 22

Bowman’s capsule

Answer 22

Blood is filtered out of Glomerulus into here

Filtrate produced contains salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules

Question 23

Proximal tubule

Answer 23

Reabsorption of ions, water, and nutrients
As filtrate passes through, materials to be excreted become more concentrated
Molecules are transported actively and passively from filtrate to interstital fluid to capillaries

Question 24

Loop of Henle

Answer 24

Descending: reabsorption of water into interstitial fluid through channels formed by aquaporin proteins; filtrate becomes increasingly concentrated
Ascending: salt diffuses from tubule into interstitial fluid; filtrate becomes increasingly dilute

Question 25

Distal tubule

Answer 25

Regulates K+ and NaCl concentrations of body fluids

Controlled movement of ions contributes to pH regulation

Question 26

Collecting duct

Answer 26

Carries filtrate through medulla to renal pelvis
Reabsorption of solutes and water to interstitial fluid
Some urea is pulled out, but most is excreted
Urine is hyperosmotic to body fluids

Question 27

Antidiuretic hormone (ADH)

Answer 27

Makes collecting duct more permeable to water
Increase in osmolarity triggers release of this, which helps to conserve water
Osmolarity of urine is regulated by hormonal and nervous control
Temporarily increases number of aquaporins in membrane of collecting ducts

Question 28

Diuretic

Answer 28

Inhibits the release of ADH: flush water out rather than reabsorb it