ZOL 355 Lecture 18 Outline of Last Lecture I Photosynthesis II CO2 fixation III Water loss issues IV C4 vs C3 plants V Challenges with water temperature VI Challenges with water buoyancy Outline of Current Lecture 1 2 3 4 Adaptations to maintain water balance Urea production Amino acids Arid environments a High temperatures b Low temperatures i Prevent freezing Current Lecture 1 adaptation to maintain water balance a marine fish maintain osmotic potential via salt production i body of fish has lower salt concentration than ocean fish is hypo osmotic relative to ocean ii water moves out of fish to ocean iii replace water by drinking seawater iv marine fish cells hypo ostomotic salt concentration is low v ocean water hyper osmotic high salt concentration vi excess salt is not tolerated it is excreted via gills and kidneys at a metabolic cost 2 Urea production in sharks balances osmotic potential a small molecules balance osmotic potential b sharks produce and retain urea 3 Amino acids in copepods are used to maintain osmotic potential 4 Seabirds remove salt via salt glands above their eyes the excreted salt drips off their beak 5 Mangroves use amino acids to control osmotic potential a mangroves live in coastal sea water environments they are hypoosmotic b water flow is out of root so it is difficult to take up water c amino acid concentrations are elevated to create osmotic balance d roots and leaves pump salt out 6 Water balance in arid environments a plants control water loss via the stomata b water loss occurs during CO2 uptake c spines and hair are used to dissipate heat and reduce evaporation 7 Challenges of high and low temperature a heat tolerance i rates of reactions increase with temp but proteins denature at high temps ii O2 consumption increases with temp 8 Mechanisms to prevent freezing a phospholipids composition of cell membranes b saturated no double bonds c unsaturated double bonds d Cold water species have more unsaturated phospholipids