Quiz 23

The process whereby animals rid their body of metabolic waste products is called:

Excretion

You just received a freshwater aquarium as a gift and decide to add more fish. When you get to the pet store, you find that the most beautiful fish are saltwater animals, but you decide to buy them anyway. What will happen when you put your expensive saltwater fish in your freshwater aquarium?

The cells of the fish will take up too much water, and the fish will die. -The osmoregulatory problems of freshwater animals are opposite to those of marine animals. Freshwater fish are adapted to life in a hypotonic environment and have mechanisms to get rid of excess water absorbed into the body. Saltwater fish are adapted to the marine environment and have extracellular fluids that have a composition similar to seawater. Placing them in fresh water will upset their osmotic balance, and they may not have regulatory mechanisms that can compensate.

Freshwater fish excrete nitrogenous wastes as _____.

ammonia -In fresh water, fish can use the abundant water passing through their gills to excrete ammonia rapidly enough so that it never reaches toxic levels in the blood. Ammonia is the easiest, lowest energy nitrogenous waste.

Osmoregulation and excretion are _____.

mechanisms that maintain volume and composition of body fluids -Both processes are crucial to maintaining homeostasis of the body's ionic composition and volume.

Terrestrial animals are _____.

osmoregulators that must obtain water from the environment -Terrestrial animals have to drink quantities of water or obtain water from their food to survive.

In animals, nitrogenous wastes are produced mostly from the catabolism of _____.

proteins and nucleic acids

Birds, insects, and many reptiles excrete nitrogenous waste in the form of uric acid, which _____.

reduces water loss compared to other nitrogenous wastes, but requires more metabolic energy to produce -Because uric acid is not very soluble in water, it can be excreted in a paste-like form with very little loss of water. However, its synthesis requires the hydrolysis of ATP.

Birds secrete uric acid as their nitrogenous waste because uric acid _____.

requires little water for nitrogenous waste disposal, thus reducing body mass

Urea is _____.

the primary nitrogenous waste product of humans

Which nitrogenous waste has the greatest number of nitrogen atoms?

uric acid