Cliffs page 203-206
Study guide questions
What is the function of the excretory system?
Maintains homeostasis by disposing metabolic wastes and control body fluid composition
Describe 2 specific examples of osmoregulation in fish.
Osmoregulation: the general process by which animals control solute concentrations and balance water gain and loss
Salt water fishes: Gain water and salt ion through drinking seawater or from food, Excretion of salt ions from gills, Osmotic water loss through gills and other parts of body surface, Excretion of salt ions and small amounts of water in scanty urine from kidneys
Fresh water fishes: Uptake of water and some ions in food, Uptake of salt ions by gills, Osmotic water gain through gills and other parts of body surface, ...view middle of the document...
A nephron eliminates wastes from the body, regulates blood volume and pressure, controls levels of electrolytes and metabolites, and regulates blood pH. Its functions are vital to life and are regulated by the endocrine system by hormones such as antidiuretic hormone, aldosterone, and parathyroid hormone. Each nephron is composed of an initial filtering component (the "renal corpuscle") and a tubule specialized for reabsorption and secretion (the "renal tubule"). The renal corpuscle filters out large solutes from the blood, delivering water and small solutes to the renal tubule for modification.
Explain how homeostasis is maintained by the action of two hormones that regulate the concentration of salts in the urine.
ADH: When blood osmolarity rises (above 300 mOsm/L), ADH is released into the bloodstream and reaches the kidneys and targets the distal tubules and collecting ducts. It makes them more permeable to water; thus, the increase in water reabsorption concentrates urine, reduces urine volume, and lowers blood osmolarity back toward the set point.
Aldosterone: Acts on the nephron's distal tubules, making them reabsorb more sodium and water and increasing blood volume and pressure
Describe the different types of waste products in animals
Ammonia: most common in marine animals due to access to lots of water; ammonia is highly soluble so it easily passes through membranes and is lost by diffusion to the surrounding water
Urea: most common in mammals, adult amphibians, sharks, turtles, some marine bony fishes; combination of ammonia and carbon dioxide; produced in the liver; advantage: low toxicity; disadvantage: uses energy to make
Uric acid: most common in insects, land snails, reptiles, birds; semisolid paste with very little water loss; advantage: easy for animals with little access to water to make; disadvantage: even more energetically expensive to produce than urea