Fresh water community and marine community

Fresh water community 

                 If the salt content and amount of dissolved substances are less, the water is considered as fresh. The fresh water habitat is generally divided into two natural divisions namely 

1. Standing water habitat 

2. Running water habitat 

Standing water habitat 

             It includes the plants like phytoplankton, rooted and submerged plants. It also includes the animal like zooplankton, fishes, turtles, mosquito, larvae, water spider, hydra and frog.

Running water habitat

                It includes aquatic plants with dissected leaves. e.g. limnophila, heterophylla and animals like larvae of dragon fly, may fly, flat worms, snails and variety of fishes.

Marine community 

              Marine community includes non-living things and living things. The most characteristic feature of sea water is its high salt content. The sea shore is divided into three main types. They are sandy shore, rocky shore and muddy shore.

Sandy shore 

               It is formed by the deposition of wave-eroded materials. Sand is a mixture of particles of various sizes. Large particles are found in the upper part of the beach. This offers no surface for attachment.

Adaptation of sandy shore animals 

                 Most of them lead burrowing mode of life. They have digging organs to burrow into the sand. They swallow the sand containing food and digest them just like earthworms. The development of respiratory siphons is a common feature among molluscs. e.g. crabs, sea urchin and sea cucumber.

Rocky shore 

               If the seashore consists of rocks and stones, then it is called rocky shore. Adaptations: A large number of sessile forms are found because rocky shore provides places for attachment. They have broad muscular foot. e.g. chiton. In some animals locomotor organs are absent. The sense organs are well developed.

Muddy shore 

                 These are formed by the deposition of silt from the water flowing into the sea from land. Poor animal population is seen due to the lack of oxygen.

Adaptations: These organisms are much more delicate than the sand dwellers. Their body is very weak and shells are very thin. They have poorly developed muscles. The burrowing organs are present in some snails. Degeneration and loss of eyes are common among mud-dwellers.