5 - Exretion and Osmoregulation Flashcards
How do phylogenetic characteristics affect excretion
Different animal groups have different excretory systems (e.g., kidneys in vertebrates, Malpighian tubules in insects)
How do air-breathers lose water
Through evaporation at respiratory surfaces (e.g., lungs in mammals and birds)
How do water-breathers regulate water and salts
Via permeable skin or gills (e.g., in fish and amphibians)
How does salinity affect excretion and osmoregulation
Marine animals: salt gain + water loss
Freshwater animals: salt loss + water gain
How does water availability influence nitrogenous waste type
Aquatic animals: excrete ammonia
Terrestrial animals: excrete urea or uric acid
How does temperature influence osmoregulation
Higher temperatures increase metabolic rate and water loss
How does food composition affect excretion
High salt diet → specialised structures like salt glands
High water content → affects urine concentration
What happens to marine fish in a hyper-osmotic environment
Lose water to surroundings
Drink seawater
Excrete salt via gills
Produce small amounts of concentrated urine
What happens to freshwater fish in a hypo-osmotic environment
Gain water passively
Do not drink water
Excrete large volumes of dilute urine
Actively absorb salts
How do sharks manage in an isosmotic environment
Retain urea in body fluids
Internal osmolarity close to seawater
Reduce water loss
Excrete salt via rectal gland
What are the main excretory structures in vertebrates
Kidneys (primary organ)
Gills (salt & nitrogen balance in aquatic species)
Salt glands (marine birds and reptiles)
What are some invertebrate excretory structures
Protonephridia/Metanephridia (annelids, mollusks)
Malpighian tubules (insects, arachnids)
Contractile vacuoles (protozoa, sponges)
How do freshwater teleosts manage osmoregulation
Gain water passively
Actively uptake salts
Produce dilute urine
How do marine teleosts manage osmoregulation
Lose water passively
Drink seawater
Excrete salt via gills
How do sharks osmoregulate
Retain urea
Maintain internal osmolarity equal to seawater
Use rectal gland to excrete salt
How do amphibians differ between life stages
Aquatic: excrete ammonia, gain water passively
Terrestrial: excrete urea, store water in bladder
What is unique about reptilian excretion
Excrete uric acid (conserves water)
Marine reptiles have salt glands (e.g., sea turtles)
How do birds manage salt and water balance
Use looped and loopless nephrons
Have salt glands in marine birds
Excrete uric acid to save water
What is the function of contractile vacuoles
Expel excess water in freshwater protozoa and sponges
How do metanephridia work in annelids/mollusks
Filter coelomic fluid
Reabsorb nutrients
Excrete waste
How do Malpighian tubules function in insects
Remove nitrogenous waste (uric acid)
Conserve water
Waste excreted with minimal water loss
