Osmoregulation
- the term for the processes by which animals control solute concentrations and balance water gain and loss
Maintaining the fluid environment of cells, tissues, and organs in animals requires keeping concentrations of water and solutes within certain boundaries; this is where osmoregulation comes in to maintain homeostasis.
Excretion
- the process that rids the body of nitrogenous metabolites and other metabolic waste products
Along with having to maintain their internal fluid environment, animals must also deal with hazardous material produced within their bodies, from various proteins and nucleic acids.
- the term for the processes by which animals control solute concentrations and balance water gain and loss
Maintaining the fluid environment of cells, tissues, and organs in animals requires keeping concentrations of water and solutes within certain boundaries; this is where osmoregulation comes in to maintain homeostasis.
Excretion
- the process that rids the body of nitrogenous metabolites and other metabolic waste products
Along with having to maintain their internal fluid environment, animals must also deal with hazardous material produced within their bodies, from various proteins and nucleic acids.
Osmoregulation in bacteria, fish, and protists vs. aquatic and terrestrial plants
BACTERIA, FISH, PROTISTS
- all marine animals maintain water balance by being osmoconformers, meaning their internal osmolarity (total solute concentration expressed as molarity) is the same as the environment - because they live in water, they are isoosmotic (the same) with their environment - marine (seawater) vertebrates must actively transport solutes in order to maintain homeostasis and in this way, they are osmoregulators because they must control internal osmolarity independent of environment - for example, marine fish, like cod, constantly lose water by osmosis and in order to make up for the loss, they drink large amounts of seawater - after this, the gills specialized cells transport sodium and chloride ions from the salt to be excreted with only a small loss of water - in this way, osmoregulation balances the uptake and loss of water and solutes - bacteria, protists, and fish that do not have cell walls cannot tolerate excessive uptake nor excessive of water, which makes them different from plants that have a cell wall - unicellular protists live in pond water, which is hypotonic to the cell and that has a much less permeable plasma membrane to slow the uptake of water (see images below) |
AQUATIC AND TERRESTRIAL PLANTS- plants share with animals the problems of obtaining water and in disposing of the surplus
- certain plants develop methods of water conservation: - ex. Xerophytes are plants in dry habitats such as deserts which are able to withstand prolonged periods of water shortage - succulent plants such as the cactus have water stored in large parenchyma tissues - other plants have leaf modifications to reduce water loss, such as needle-shaped leaves, sunken stomata and thick, waxy cuticles as in the pine - ex. the sand-dune marram grass has rolled leaves with stomata on the inner surface - the cell wall plays a vital role in transporting nutrients and excess water through the plant (helps maintain cell's water balance that can opposite further water uptake: called turgor pressure |