Aquatic environments share certain characteristics . Temperatures in water change slowly and are not so extreme as temperature changes on land. Water supports the bodies of living things. Water life forms do not need to be as concerned about supporting their bodies as land life forms. Living things that live in water are not in danger of dehydration.
Water is more dense than air.
Creatures that need to move swiftly in water develop streamlined shapes. Light does not penetrate far into water. Nutrients in the water come from the decomposition of existing life forms or are washed into the water from the land. Some Types of Communities Conditions Life Forms Intertidal Zone Between the high and low tide levels Alternately wet and dry. Estuary Water is mixture of fresh and saline.