Excretory System Basics & Nitrogenous Wastes

Excretory systems

systems that remove waste materials and maintain homeostasis

Basic function removing soluble wastes

removes soluble wastes from body fluids

Basic function ion nutrient water balance

maintains ion nutrient and water balance in the animal

Basic function removing nitrogen wastes

removes nitrogenous wastes from protein and nucleic acid metabolism

Wastes filtered by gills

gills filter wastes in some animals

Wastes filtered by lungs

lungs eliminate carbon dioxide

Wastes filtered by kidneys

kidneys filter wastes from the body

Wastes filtered by body surfaces

skin removes wastes in some animals

Nitrogenous wastes

wastes that must be removed because they are toxic

Forms of nitrogen waste

ammonia ammonium ions urea uric acid

Waste form depends on environment

type of waste produced depends on organism and environment

Ammonia and ammonium ions

most toxic nitrogenous wastes

Ammonia toxicity

disrupts pH and oxidation-reduction reactions

Aquatic animals waste

aquatic animals most commonly produce ammonia

Marine invertebrate ammonia excretion

excreted across skin and gills

Fish ammonia excretion

gills and kidneys excrete ammonia in freshwater and marine fish

Immediate excretion of ammonia

ammonia excreted as soon as formed because of toxicity

Advantage of ammonia excretion

requires no energy to remove

Disadvantage of ammonia excretion

requires considerable body water for safe concentrations

Urea

nitrogen waste produced by mammals most amphibians some fish reptiles terrestrial invertebrates

Urea formation

produced from protein and amino acid metabolism

Advantage urea toxicity

less toxic so small accumulations tolerated

Advantage urea water

requires little water to excrete

Disadvantage urea energy

requires moderate energy to form and break down

Uric acid

waste from breakdown of nucleic acids and some proteins

Animals producing uric acid

birds insects most reptiles

Uric acid toxicity

less toxic but energy costly to produce

Uric acid solubility

not soluble in water and not excreted as liquid urine

Uric acid excretion form

secreted as semisolid with other wastes without water loss