Lecture 15 Flashcards
water and salt physiology II
What environments pose challenges to animals and their maintenance of physiological homeostasis?
Animals face challenges to physiological homeostasis in extreme environments, such as deserts with limited water, where dehydration threatens, or cold climates, where maintaining body temperature is difficult. Additionally, aquatic environments with varying salinity, like estuaries, challenge animals to regulate osmotic balance and ion concentrations.
What is the difference between catadromous and anadromous species, and can you give examples?
Catadromous species, like the European eel, migrate from freshwater to seawater to spawn. Anadromous species, like salmon, migrate from seawater to freshwater to spawn.
What does it mean for an eel to be hyperosmotic in freshwater and hypoosmotic in seawater?
In freshwater, eels are hyperosmotic, meaning their body has a higher concentration of solutes than the surrounding water, so they must prevent excess water from entering their body. In seawater, they are hypoosmotic, meaning their body has a lower concentration of solutes compared to the seawater, so they must prevent dehydration by excreting excess salt.
How do gills function differently when animals are in freshwater versus seawater?
In freshwater, gills pump ions into the body to maintain osmotic balance. In seawater, gills pump ions out of the body to prevent dehydration and maintain salt balance.
Why is osmotic regulation critical for aquatic animals that migrate between freshwater and seawater?
Osmotic regulation is critical because these animals must maintain proper internal salt and water balance as they move between environments with vastly different salinity levels, ensuring cellular function and survival.
How do freshwater animals regulate their blood compared to the surrounding water?
Freshwater animals are hyperosmotic to the surrounding freshwater, meaning their body fluids have a higher concentration of solutes than the water.
How do freshwater animals manage water and ion balance?
Freshwater animals gain water by osmosis and lose ions by diffusion. They must counteract this water influx and ion loss to survive.
What are the three factors that determine the rates of passive exchange of water and ions in freshwater animals?
- The magnitude of ion and osmotic gradients between the animal’s blood and the surrounding water.
- The permeability of the animal’s outer body.
- The surface area across which exchange occurs.
Why is the evolution of more dilute blood important for freshwater animals?
Evolution of dilute blood helped freshwater animals survive in freshwater environments, where body fluids with high concentrations of solutes would otherwise be incompatible with life.
How do freshwater animals minimize water gain and ion loss across their body?
Freshwater animals have low permeability to ions and water across their skin, which helps reduce water gain and ion loss by diffusion and osmosis.
How do freshwater animals handle the excess water gained by osmosis?
They produce large volumes of hypoosmotic urine (with lower ion concentrations than their blood), helping to remove excess water while retaining ions.
How do freshwater animals replace ions lost through diffusion and urine production?
They actively transport ions back into the body from the environment, often using specialized pumps that require ATP.
What is the process for actively transporting ions in freshwater animals?
Active transport mechanisms pump ions into the body against the gradient and require ATP, with different mechanisms for different ions.
What role do gills play in ion and oxygen exchange in freshwater animals?
Gills are the primary site for both oxygen exchange and ion uptake in freshwater animals, especially during early development.
How does the gill epithelium function in freshwater animals?
The gill epithelium consists of Mitochondrial-rich cells (MRC) for ion uptake and pavement cells for gas exchange. MRCs can increase in soft water environments with low Ca2+ concentrations, but this may interfere with oxygen uptake.
