BIOL 103 Lecture Notes - Allantois, Saltwater Fish, Osmosis

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Biology Lecture #5 Excretion and Ion Transport
Lecture covers nitrogenous wastes, salt and water balance as well as kidney function
Obligatory Exchanges
Many vital processes have potential to disturb the balance between salt and water concentrations
Obligatory exchanges are necessary as part of respiration or elimination of wastes
Water and salt will be loss through body respiration, ingestion of food will be eliminated as waste
(unnecessary parts) as well as through metabolism
Nitrogenous Waste
Product of the breakdown of amino acids and nucleic acid degradation
The waste produced is species and environment dependent, such as ammonia, urea and uric acid
Most aquatic animals excrete ammonia or ammonium ions
Little energy required for prudction, high amount of water needed to excrete and has high
toxicity
Most mammals, amphibians, marine fishes and terrestrial invertebrates excrete urea
Requires moderate energy and moderate amount of water for excretion, has a low toxicity
Birds, insects and most reptiles excrete uric acid
Requires a lot of energy but little water to excrete, and has a low toxicity
Example of a freshwater fish
Body is hyperosmotic and danger of being water logged due to constant osmotic pressure of
water which is why water travels in from gills via osmosis
Produce large amount of dilute urine to remove water
Risk of losing salts, so taken in by active uptaking of na+ and cl- into their capillaries
Example of a Saltwater fish
Body is hyperosmotic and in danger of dehydrating with water lost across their gills
Need to drink much seawater
Excreted ammonia is diluted with as little water as possible, meaning urine is concentrated
Excess salt is transported out of body by specialized cells in the gills
Anatomy of Bird Egg
Uric acid is stored in allantois and left behind at hatching
Metabolic processes still occur inside an egg
Excretory Organs
Filtration remove water and small concentrations of solutes from body fluids or blood while
leaving behind important things such as blood cells, proteins and other large solutes
Reabsorption useful material in the filtrate, recaptured and sent to blood stream
Secretion put additional solutes into the filtrate and can help aid in elimination of toxins