1 2 3 4 5 6

environment. Most animals are osmoregulators, who use some mechanism to adjust their internal body fluids. Let's outline the basic problems with each environment and think of potential coping strategies.

Salt Water hypertonic Out In Osmoconformer Take in water Excrete salt small high ocean fish

Fresh water hypotonic In Out

Air (land) N.A. Out No change take in water reduce H2O loss regulate salt varies varies

ysof environment Water movement Ion movement Coping strategies

pump out water Take up salt large low

Amount urine (vert.) solute concentration Examples:

freshwater fishmammals, earthwormsbirds, insects Paramecium (p.139)

The first thing to ask yourself when confronted with a question of how an animal copes with water issues is - what environment does it live in? 1.Osmoconformers Many marine invertebrates conform to the osmolality of their surroundings although they may still regulate the concentrations of some ions. Most vertebrates are hypotonic to sea water. A few solve the osmotic problem by keeping their solute concentration close to their surroundings. Primative jawless fishes are isotonic with sea water. Cartilaginous fishes such as sharks maintain lower levels of salt, but retain urea, a soluble waste product of nitrogen metabolism. 2. Terrestrial vertebrates It is harder to make generalizations about terrestrial animals - the challenges/solutions will vary with the particular environment. It's different to be a river otter than to be a desert kangaroo rat. Terrestrial animals need to balance water gain and loss.