GENBIO 4TH

• Osmoregulation


  Regulation of water uptake and loss of the organism compared to environment
• Maintaining fluid balance


  • Requires that the relative concentration of solutes and water be kept within narrow limits
• Functions of osmoregulation


  • Controls solute concentrations and balances water gain and loss
  • Deals with waste accumulation and toxicity
• Osmoconformers


  Isosmotic with their surroundings and do not regulate their osmolarity
• Osmoregulators


  Expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment
• Osmoregulators


  • Marine animals
  • Freshwater animals
• Most animals are stenohaline; they can't tolerate substantial changes in external osmolarity
• Euryhaline animals can survive large fluctuations in external osmolarity
• Marine invertebrates


  • Most are osmoconformers
• Marine vertebrates


  • Most are osmoregulators
  • Balance water loss by drinking seawater and eliminating salts through gills and kidneys

  
• Sharks have high concentration of urea but trimethylamine oxide (TMAO) protects them from its denaturing effect
• Freshwater animals


  • Constantly take in water by osmosis
  • Lose salts by diffusion
  • Maintain water balance by drinking almost no water and excreting dilute urine
• Osmoregulation in marine fish

  1. Gain of water and salt ions from food and drinking seawater

  2. Excretion of salt ions from the gills

  3. Excretion of small amount of water and salt ions in scanty urine from kidneys

  
• Osmoregulation in freshwater fish

  1. Gain of water and some ions in food

  2. Uptake of salt ions by gills

  3. Excretion of salt ions and large amounts of water in dilute urine from kidneys

  4. Osmotic water gain through gills and other body surface

  
• Anhydrobiosis


  Adaptation of some aquatic invertebrates in temporary ponds to lose almost all their body water and survive in a dormant state
• Adaptations of land animals

  • Body coverings to prevent dehydration
  • Nocturnal lifestyle in desert animals
  • Obtaining water from moist food and metabolic processes
• Transport epithelia


  Epithelial cells specialized for controlled movement of solutes in specific directions, arranged into tubular networks
• Transport epithelia


  • Nasal glands of marine birds that remove excess sodium chloride from the blood

  
• Forms of nitrogenous waste

  • Ammonia
  • Urea
  • Uric acid

  
• Ammonia is the simplest nitrogenous waste, released directly by many invertebrates

  
• Urea is less toxic than ammonia and excreted by most terrestrial mammals and many marine species
• Uric acid is excreted by insects, land snails, and many reptiles including birds
• Functions of excretory systems

  • Filtration
  • Reabsorption
  • Secretion
  • Excretion
• Excretory systems


  • Protonephridia in flatworms and some molluscs
  • Metanephridia in earthworms
  • Malpighian tubules in insects
  • Kidneys in vertebrates

  
• Nephrons


  Functional units of the vertebrate kidney, including cortical nephrons and juxtamedullary nephrons
• Bowman's capsule


  Produces the filtrate containing salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules