How Life Evolved in the Ocean
Biodiversity
Recent species inventories, conducted by the Census of Marine Life(CoML) and the World Register of Marine Species (WoRMS), have revealed a total of 228,445 marine species, which represents only about 13 percent of the total 1.8million species on Earth, with the vast majority of species (87%) inhabiting terrestrial or freshwater environments.
Why Are There So Few Marine Species?
Oceans are and old, stable, homogeneous environment compared with terrestrial habitats.
- for example rainforest. Plants both above and below ground, provides a much greater chance for natural selection to act on populations, to generate new species via evolution.
Convergent Evolution
In which distantly related organisms, such as dolphins and sharks, independently evolve similar features, such as streamlined bodies and fins and countershading coloration.
Other marine examples include the independent evolution of jet propulsion in squids and scallops, and ventral counterillumination using bioluminescence in pelagic squid and numerous marine fish groups, such as lanternfishes and dragonfishes.
In ventral counterillumination, organisms use bioluminescence to match any sunlight coming from above, obscuring their silhouette to predators lurking beneath them.
Origin of Life on Earth
Scientists have proposed hot springs, shallow seas, and tide pools as likely birthplaces.
Recent evidence, however, suggests that the oldest habitable environments for life on Earth may have been submarine hydrothermal vents.
How Did Evolution Shape the Organisms That Live in the Ocean.
Environments of deep-sea
- Dark
- Cold
- Highly pressurized
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Features of deep-sea fishes
- long fangs
- light-producing structure: attract preys, communicate
- huge jaw & stomachs: because of scarce prey item
(Example - Chiasmodon niger)