LECTURE 10: Adaptation to Water and Ions

• Homeostasis - the maintenance of the steady states in the body and the physiological processes with which these states are regulated
• Homeostasis was coined by American physiologist Walter Bradford Cannon.
• Homeostasis - “maintenance of nearly constant conditions in the internal environment”
• Endothermic animals maintain internal body temperature
• Levels of blood sugar (glucose), ions, and water are maintained within normal limits.
• Methods of Homeostatic Regulations: Reactive and Predictive
• Reactive Homeostasis - direct response to changes in the internal environment
• Predictive Homeostasis - direct response to changes in external environment.
• Peruvian parrots practice geophagy or consumption of soil, in this case clay.
• Clay helps these birds eat more toxic plants.
• Osmoregulation - otherwise known as water and osmotic regulation
• Osmoregulation - regulation of water volume and salt concentration inside the animal body
• Osmoregulation - refers to control of the amount of water, and levels of mineral salts and ions in blood
• Hypertonic environment - the RBC shrinks as the net movement of water is out of the cell.
• Isotonic environment - the RBC maintains its shape as the net loss of water is zero.
• Hypotonic environment - the RBC bloats beyond its normal size
• Osmoconformers - match their body’s osmolarity to their environment
• Osmoconformers - incapable of tolerating wide variations in salinity
• Osmoregulators - maintain conditions of their internal environment

  stable within narrow limits in the face of variations of conditions in the external environment
• Osmoconformer - Many marine invertebrates are isosmotic with their environment.
• Osmoconformer bodies are permeable allowing changes in the concentration of solutes inside their bodies in response to any osmotic change in the environment.
• Stenohaline Organism - are aquatic organisms with ability to adapt to narrow range of salinities
• Stenohaline Organisms - either live in freshwater or marine environment but never in both; are mostly osmoconformers
• A goldfish is a stenohaline organism.
• Osmoregulator - capable of long migrations and can change habitats from freshwater rivers to coastal seas and back to freshwater rivers
• Atlantic salmon are osmoregulators
• Mammals are osmoregulators as these keep conditions in their internal environment stable.
• In a freshwater environment fishes actively take in salts through their

  gills and water through their skin. These fishes also release a very dilute urine.
• In a saltwater environment fishes drink seawater and excrete salt through their gills and urine.
• Euryhaline Organisms - Can adapt to wide range of water salinities
• Contractile Vacuole - is a tiny spherical intracellular vacuole among

  sponges and radiate animals (cnidarians & ctenophorans)
• Contractile Vacuole - not an excretory organ but rather functions for

  water balance
• Nephridium - most common type of invertebrate excretory organ
• Nephridium - tubular structure designed to maintain osmotic balance
• Nephridium: may be the primitive protonephridium or more advanced metanephridium
• protonephridium (singular) has two highly branched duct systems throughout the body because acoelomate animals do not have circulatory system to transport waste to an excretory organ.
• Protonephridia is a closed system.
• Protonephridia can be a flame cell system in acoelomates (flatworms) and some pseudocoelomates.
• Metanephridia

  • advanced type

  • found in several eucoelomates like molluscs and annelids
• Metanephridia is an open system