Adaptation to Environment: Strategies for Survival

Abstract

Of the three major environments found in the world today, fresh water is intermediate in character between sea and land—the former being stable and relatively uniform, the latter spanning a diverse range of habitats, many of which have fluctuating seasonal conditions. Though similar to the sea in being aquatic, freshwater habitats demonstrate a wide range of character, comparable to that found on land. In terms of water chemistry, inland waters range from those with practically no salts to brine lakes, in temperature from permanently frozen lakes to hot springs, in stability from the profundal regions of large lakes (where conditions are constant) to temporary pools (which dry up each year), and so on. In all these habitats ‘freshwater’ organisms exist and thrive. The present chapter examines the conditions in major habitats and illustrates how organisms are adapted to them. The examples cited highlight the major adaptations and should not be considered a comprehensive coverage of the enormous variety of form and function found among freshwater organisms.