Theme 4 Flashcards
homeostasis
The maintenance of a steady internal environment
challenges of homeostasis in marine/terrestrial/freshwater environment
organisms in marine and terrestrial environments require mechanisms to obtain and conserve water; freshwater environments do not.
obtaining salts and ions is easy in marine environments, but more difficult in freshwater and terrestrial environments.
osmosis
water molecules move across a selectively permeable membrane from a region of low solute concentration to high solute concentration
osmolarity (useless but additional info)
the number of solute molecules and ions per litre of solution
hyperosmotic vs hyposomotic
In hyperosmotic, the total amount of solutes in a solution is greater than that of another solution.
In hyposomotic, the total amount of solutes in a solution is less than that of another solution.
how does solute concentration determine freezing point and boiling point of solution
Increasing solute concentration reduces the freezing point and increases the boiling point of a solution.
osmoconformers
animals that osmotic concentrations of the cellular and extracellular solutions simply match that of the environment.
marine invertebrates, hagfish and elasmobranchs as osmoconformers
when placed in dilute sea water, the osmotic concentration of their body fluids decreases and their weight increases as a result of the osmotic influx of water
osmoregulators
animals that use control mechanisms to keep the osmolality of cellular and extracellular fluids constant (i.e., homeostatically controlled) but at levels that may differ from the osmolality of the surroundings.
osmoregulators organisms
Most freshwater and terrestrial invertebrates, and almost all vertebrates
true or false: Cells must control their ionic and pH balance, water & solutes concentration, nutrients, gases, waste products, volume, pressure, temperature
true
Excertion
elimination of waste/toxins, aids in controlling content of extracellular fluid (salt/water/pH)
how is exertion tied to osmoregulation?
Animals excrete toxic products of metabolism, such as nitrogen-containing compounds resulting from the breakdown of proteins and nucleic acids, and breakdown products of poisons and toxins. The excretion of ions and metabolic products is accompanied by water excretion because water serves as a solvent for those molecules.
there are 4 steps of exertion
a- Filtration: the nonselective movement of water and a number of solutes ions and small molecules, but not large molecules such as proteins.
b- Reabsorption: molecules (e.g., glucose and amino acids) and ions are transported back into the extracellular fluid and into the blood as the filtered solution, basically the system takes back the solutes it wants to keep.
c- secretion: a selective process in which specific small molecules and ions are transported from the extracellular fluid and blood into the tubules for eliminating particular substances from the body fluid or blood.
d- exertion: urine is released into the environment.
metabolism of ingested food produces
metabolic water
Ammonia
Ammonia results from the metabolism of amino acids and proteins and is highly toxic: it can be safely transported and excreted from the body only in dilute solutions.
Urea
All mammals, most amphibians, some reptiles, some marine fishes, and some terrestrial invertebrates combine ammonia with HCO3– and convert the product in a series of steps to urea, a soluble substance that is less toxic than ammonia. Although producing urea requires more energy than forming ammonia, excreting urea instead of ammonia requires much less water
Uric acid
Water is conserved further in some animals, including many terrestrial invertebrates, reptiles, and birds, by the formation of uric acid instead of ammonia or urea. Uric acid is nontoxic, but its great advantage is its low solubility. it can be expelled with minimal water
all freshwater invertebrates are osmoregulators, therefore they’re
hyperosmotic relative to their environment, causing water to move constantly from the surroundings into their bodies
marine invertebrates (sponges, cnidarians, some molluscs, and echinoderms) are osmoconformers, therefore they
do expend energy to keep some ions, such as Na+, at concentrations different from the concentration in sea water.
freshwater invertebrates (osmoregulators) obtain salts…
they need from foods and by actively transporting salt ions from the water into their bodies
true or false: freshwater invertebrates can live in more varied habitats than osmoconformers can.
true
Terrestrial osmoregulators Although they do not have to excrete water entering by osmosis, they
they must constantly replace water lost from their bodies by evaporation and excretion. Most obtain water from their food, and some drink water. Like their freshwater relatives, these invertebrates must obtain salts from their surroundings, usually in their foods.
protonephridia has specialized Excretory Tubules that participate in Osmoregulation
the excretory tubules are open only at one end. Body fluids do not enter protonephridia directly. An ultrafiltrate enters the tubule through narrow extracellular spaces that permit only small molecules to enter, and exclude larger mole- cules such as proteins
