EXCRETORY SYSTEMS
Controlling the Internal Environment
Functions of Excretory System
Maintaining
Open
the ‘internal pond’
circulatory system Closed circulatory system
Water balance
Uptake
and loss of water
Disposing
of metabolic wastes
H+, salts
Nitrogenous,
Nitrogen Waste Products From Proteins & Nucleic Acids
Ammonia
NH3 Aquatic
animals (fish)
Urea
Mammals, most amphibians
Uric
Acid
Birds Reptiles Insects
What Factors Determine N2 Waste Product?
Energetic Toxicity
Abundance
expense
of water Environment Presence of amniotic egg
Why NH3?
Metabolically
easy to make—little energy required. But…very toxic! How does it work?
If abundant water is not available?
UREA!
How Does a Shelled Embryo Dispose of Waste?
Uric Acid and Shelled Eggs
Uric
acid is stored
Uric acid is not water soluble or toxic.
Effect of Environment….
Abundant
NH3
water available….
Less
water available…. less water available….
acid
Urea
Even
Uric
Types of Excretory Systems
Protonephridium
Platyhelminthes
Metanephridium
Annelida
Malpighian Kidney
System
(insect)
Arthropoda
Vertebrate
How Regulation Occurs
Diffusion down concentration gradient Ex.: urea Transport of solutes Against concentration gradient Transport epithelium Ex.: Na+, uric acid Osmosis Movement of water from one area to another.
Water Balance
Osmolarity
solute concentration Tonicity
Determines
Total
direction of water
movement Controls uptake and loss of water in cells and organisms
Platyhelminthes
Protonephridium
Metanephridium of Earthworm
Metanephridium
Metanephridium of Earthworm
ANNELID X-Section
Metanephridium
ANNELID
Metanephridium
Nephridiopore
These excretory organs open through nephridiopores on the ventral surface of the body wall.
Malpighian Tubules
Malpighian Tubules