Editing Water (section)

===Aquatic life forms===
{{Further|Hydrobiology|Marine life|Aquatic plant}}
Earth's surface waters are filled with life. The earliest life forms appeared in water; nearly all fish live exclusively in water, and there are many types of marine mammals, such as dolphins and whales. Some kinds of animals, such as [[amphibian]]s, spend portions of their lives in water and portions on land. Plants such as [[kelp]] and [[algae]] grow in the water and are the basis for some underwater ecosystems. [[Plankton]] is generally the foundation of the ocean [[food chain]].

Aquatic vertebrates must obtain oxygen to survive, and they do so in various ways. Fish have [[gills]] instead of [[lungs]], although some species of fish, such as the [[lungfish]], have both. [[Marine mammal]]s, such as dolphins, whales, [[otter]]s, and [[pinniped|seals]] need to surface periodically to breathe air. Some amphibians are able to absorb oxygen through their skin. Invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters including breathing tubes (see [[Siphon (insect)|insect]] and [[Siphon (mollusc)|mollusc siphons]]) and [[gills]] (''[[Carcinus]]''). However, as invertebrate life evolved in an aquatic habitat most have little or no specialization for respiration in water.

{{gallery
|align=center
|File:Blue Linckia Starfish.JPG|Some of the [[biodiversity]] of a [[coral reef]]
|File:Diatoms through the microscope.jpg|Some marine [[diatom]]s – a key [[phytoplankton]] group
|File:VonDamm Crustaceans.jpg|[[Squat lobster]] and [[Alvinocarididae]] shrimp at the Von Damm [[Hydrothermal vent|hydrothermal field]] survive by altered water chemistry.}}