Marine life appeared in the form of fish, which live exclusively in water. Some of these evolved into amphibians which spend portions of their lives in water and portions on land. Other fish evolved into land mammals and subsequently returned to the ocean as seals, dolphins or whales. Plant forms such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton, and particularly phytoplankton, are key primary producers forming the general foundation of the ocean food chain. Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters including breathing tubes (see
Forensic limnology water conducting tissues, which affects their dispersion throughout ecosystems. These microscopic organisms mainly inhabit freshwater environments because of their inability to survive with the cleaning agents present in domestic water sources. Diatoms are identifiable based on each species unique silica cell walls and vary depending on their environment. Because they have determinant properties diatoms create flora profiles for scientists. When these microscopic algae die, their frustules (silica cell walls) becomes a part of the water sediment. The presence of the frustules enables scientists to compare the cell walls of the deceased organisms with the living diatoms to determine characteristics of