Osmoregulation & Excretion

Osmoconformers

Consisting only of some marine animals, are iso-osmotic with their surroundings and do not regulate their osmolarity.

Excretion

Different animals excrete nitrogenous wastes in different forms. • Ammonia- Most fish • Urea- conversion to urea in energetically expensive; saves water, less toxic; mammals, amphibians, some fish. • Uric acid- more expensive than urea but MOST amount of water saved; insects, land snails, and many reptiles, all birds.

Tardigrade "water bear"

are able to remain in a state of anhydrobiosis

Osmoregulators

expand energy to control water uptake and loss in a hyper-osmotic or hypo-osmotic environment

Fresh Water animals

live in a hypo-osmotic environment= very low solute •Fw animals constantly take in water by osmosis from their hypo-osmotic environment. •FW aquatic inverts in ventral ponds: dump all body water and survive in a dormant state. -State= anhydrobiosis an=lack of Hydro=water biosis = life

Marine Animal

• Most marine invertebrates, Sea squirts, hagfish (only vert), cartilaginous fish** = osmoconformers - Sharks maintain very high concentration of solutes and urea in body- slightly greater than that of sea water. -so they are~iso-osmotic and don't have to drink water •Most marine vertebrates, like bony fish are osmoregulators.

Urea as a fertilizer

• NPK ration is 46-0-0. • 90% of world industrial production of urea is for fertilizer •Recent Study of fertilizer- Dead zones results from excess nitrogen causes plants to not grow or grow rapidly and die. •15% of fertilizer put down in 1982 is stored in soil, awaiting releases into water . . . more dead zones to come

Osmoregulation

•Regulates solute concentrations and balances the gain and loss of water • Osmoconformers •Osmoregulators

Least Wateful

•The amount of nitrogenous waste is coupled to the animal's energy budget •**Making Waste- Key functions of most excretory systems: -Filtration: pressure- filtering of body fluids -Reabsorption: reclaiming valuable solutes -Secretion: adding toxins and other solutes from the body fluids to the filtrate -Excretion: removing the filtrate from the system