Excretion and Osmoregulation

• Osmoregulation - How animals control solute concentration and balance water gain & loss.
• Osmoregulation

  A) Hyperosmotic

  B) isoosmotic

  C) hypoosmotic

  
• Excretion - Elimination of nitrogenous metabolites & other metabolic waste products
• Primary metabolic waste products in animals:

  • CO2 – excreted thru respiration

  • Water & Nitrogenous wastes – removed by excretory organs
• Ammonia

  A) toxic

  B) water

  C) low

  D) aquatic

  E) proteins

  F) nucleic

  G) low

  
• Urea

  A) Ammonia

  B) Carbon Dioxide

  C) liver

  D) less

  E) small

  F) large

  G) mammals

  H) amphibians

  
• Uric Acid

  A) toxic

  B) water

  C) insoluble

  D) largest

  E) reptiles

  F) insects

  G) snails

  
• Variations of how nitrogenous waste is formed

  A) Nitrogenous Bases

  B) Amino Acids

  
• EXCRETION AND OSMOREGULATION STRATEGIES

  1. CONTRACTILE VACUOLES of protists
  2. PROTONEPHRIDIA in planaria
  3. METANEPHRIDIA of annelids and mollusks
  4. MALPIGHIAN TUBULES of arthropods
  5. OSMOREGULATION AND METABOLIC WASTE DISPOSAL in vertebrates
• Contractile vacuoles of protists


  Periodically contracts to expel excess water out of body
• Cycle of collecting & expelling water

  1. Diastole - water moves from environment to contractile vacuole

  2. Systole - contractile vacuole contracts, expels water out of cell
• In hypertonic environments


  Cell adjusts cytoplasm to be more hypertonic than environment
• Common in


  • Unicellular algae
  • Some marine & soil microorganisms
• Contractile vacuole


  Different from food vacuole (food storage)
• Contractile vacuoles


  • Some have >1
  • Others have none and none in multicellular organisms
• Contractile vacuoles


  Some present in unicellular stage (ex. Multicellular fungi)
• Amoebas


  Use exocytosis - vacuoles/vesicles merge with cell membrane to expel toxic wastes & excess water
• Paramecium


  Contractile vacuole is surrounded by several canals
• EXCRETION AND OSMOREGULATION STRATEGIES

  KEY STEPS

  A) blood

  B) Body Fluids

  C) toxins

  D) ions

  
• PROTONEPHRIDIA IN PLANARIA


  • Network of dead-end tubules lacking internal openings

  • Flame cells (motion looks like flame) with clusters of cilia at the end of tubules
• PROTONEPHRIDIA IN PLANARIA

  Steps:

  • Filtration: water & solutes drawn into flame bulb

  • Filtrate released into tubule network & propelled to

  tubules thru cilia

  • Processed filtrate exits thru tubules

  • Urine empties via external openings

  
• METANEPHRIDIA OF ANNELIDS & MOLLUSKS

  • A pair is found in annelids

  • Steps:

  • Ciliated funnel draws water into collecting tubule

  • Hypoosmotic filtrate produced (earthworms in damp soil --> net water uptake)

  • Transport epithelium reabsorbs most solutes

  • Nitrogenous wastes excreted to environment

  A) segment

  B) coelomic

  
• MALPIGHIAN TUBULES OF ARTHROPODS


  • Steps:

  • Transport epithelium in tubules secretes solutes (with N-wastes) from hemolymph

  • Water follows into tubule by osmosis

  • Most solutes are pumped back into hemolymph

  • Water reabsorption by osmosis

  • N-wastes (mainly uric acid) eliminated with feces

  
• OSMOREGULATION AND METABOLIC WASTE DISPOSAL IN VERTEBRATES


  Osmoconformers

  • Body osmolarity matches environment --> no tendency to gain/lose water

  • Ex. Marine animals

  • Even if internal environment is isosmotic to external environment, ions vary greatly
• OSMOREGULATION AND METABOLICWASTE DISPOSAL IN VERTEBRATES

  Osmoregulators

  • Internal environment of organisms remains constant despite osmotic pressure changes in environment

  • Actively controls salt concentrations in body

  • More common than osmoconformers
• OSMOREGULATION AND METABOLIC WASTE DISPOSAL IN VERTEBRATES

  Freshwater fish

  • Hypotonic environment (bodies have higher salt concentraition than environment)

  • Tendency to be waterlogged --> need to osmoregulate

  • Water comes in --> Na+ & Cl- ions move out

  • Adaptations:

  >Don’t drink water except in food

  >Kidneys produce large amounts of urine

  >Cells in gills pick up ions from water --> transported in blood

  A) gills

  B) body surface

  
• OSMOREGULATION AND METABOLICWASTE DISPOSAL IN VERTEBRATES


  • Stenohaline (Gr. stenos, narrow; halos, salt)

  > Most animals

  > Tolerates narrow range of salinity
• OSMOREGULATION AND METABOLIC WASTE DISPOSAL IN VERTEBRATES


  • Euryhaline organisms (Gr. eurys, broad)

  > ex. salmon

  > Can tolerate wide range of salinity

  > Euryhaline osmoconformers – barnacles & mussels in

  estuaries

  > Euryhaline osmoregulators – striped bass & salmon

  
• OSMOREGULATION AND METABOLIC WASTE DISPOSAL IN VERTEBRATES


  Amphibians

  • In freshwater: excrete large amount of

  dilute urine

  > Active transport of salt in skin

  > Mainly ammonia

  • On land: water reabsorption in urinary

  bladder

  > Excrete urea

  
• OSMOREGULATION AND METABOLIC WASTE DISPOSAL IN VERTEBRATES


  Birds

  • N waste: uric acid

  > Excreted as paste

  > Reduces water loss
• OSMOREGULATION AND METABOLIC WASTE DISPOSAL IN VERTEBRATES


  Terrestrial vertebrates

  • Lungs - Excrete CO2 & some water

  • Skin – sweat glands excrete perspiration (5-10% metabolic wastes)

  • Liver – produces urea & uric acid (processed by kidneys)

  > Material recycling --> intestines for disposal in rectum
• OSMOREGULATION AND METABOLIC WASTE DISPOSAL IN VERTEBRATES

  Saltwater fish

  • Hypertonic environment (salt conc. in bodies is lower than environment)

  > Constantly loses water

  • Adaptations:

  > Drink seawater --> high intake of salts

  > Cells in gills transport salt from blood into water

  > Small volume of urine

  A) gills

  B) urine