01:460:120 Lecture Notes - Lecture 21: Scleractinia, Fringing Reef, Autotroph
18 Apr 2017
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Document Summary
Corals first appeared in the fossil record over 400 million years ago. Corals evolved into more modern reef-building, colonial forms about 25 million years ago. Coral reefs are the largest structures on earth that result from biological activity. Most coral reefs go through 3 stages of development: o o. Coral reefs are complex ecosystems; although they cover <1% of the ocean bottom, they are the home of 25 % of all marine life. The prodigious productivity of coral reefs is due to symbioses between unicellular autotrophic algae (zooxanthellae) and coral. Corals are related to sea anemones and jellyfish. There are two groups of corals; o o. Stony corals are the group responsible for building up reefs, they do this by secreting calcium carbonate, caco3. For the most part, stony corals are colonial organisms composed of hundreds to hundreds of thousands of small individuals, called polyps, which are typically only 1-3mm in diameter. Corals have a symbolic relationship with unicellular algae.
