Coral: It's Really Not a Plant Quiz

Answer: Absence of a cell wall

Using a microscope, William Herschel was able to distinguish thin animal cell membranes in coral. Herschel was a German astronomer and composer, who is renowned for having discovered Uranus.

Plant cells have both a cell membrane and cell wall, where as animal cells lack a cell wall. (credit to hackworr)

Answer: Polyps

Clustered together in compact colonies, each individual polyp is sac-like and is a few millimetres in diameter and a few centimetres in length. They are classified as marine invertebrates in the class Anthozoa of phylum Cnidaria.

Answer: Tentacles

Coral have stinging cells on their tentacles. The tentacles on each polyp are retracted during the day and spread out at night. Polyps are linked by gastrovascular canals and allow the individual polyps to share food. (credit to Kino76)

Answer: False

Coral is a living creature. Outside of water it will die. As with anything, once it has died, it is dead. When you rehydrate dead coral it goes from being dry dead coral to wet dead coral. African lungfish have evolved to such a degree that they can breathe air when necessary.

They can survive in hardened mud in dried up stream beds for extended periods of time. Its swim bladder can serve as a lung. (credit to Kino76)

Answer: Night

Sunset is the cue for the spawning to begin. As they are nocturnal, all coral spawns on the same night and the time is dictated by temperature change and well as the cycle of the moon. Gametes fuse and form a larva called a planula. One downside of this type of reproduction is that hybrid species often evolve. (credit to hackworr)

Answer: Calcium carbonate

Each individual polyp starts secreting the exoskeleton from its base. Over time a large limestone skeleton develops and this is what builds coral reefs. The skeleton body is white and all the brilliant colours come from tiny algae called "zooanthellae" which live inside the polyp tissue and produce pigments. (credit to hackworr)

Answer: Decreased water temperature

Statistically, 10% of the world's coral reefs are dead. 60% of reefs are currently at risk from human activities like coral mining, canal digging and pollution. Ocean acidification, sea level rise and increased water temperature are thought to contribute to the dying off of coral reefs. Coral bleaching is also a result of increased temperature changes which cause the coral to expel symbiodimium (algae), which causes the coral to reveal their white skeletons. (credit to Kino76)

Answer: Bone grafts

Coral is naturally suitable to be used for bone grafts. Its osteoconductivity makes it suitable for hard tissue regeneration and coral's matrix closely resembles natural bone structure. It does need to be converted from its calcium carbonate base into something more organic though and needs a bone product to make it more osteoconductive. Coral bone grafts have been used predominantly in maxillofacial reconstructive surgery, but have also been tested in spinal fusion and fracture repair.

(credit to Kino76)

Answer: Coral Rag Formation

Coral is crushed into smaller pieces and used for building walls, but has also been used to build some of the oldest buildings in England. St. George's Tower of Oxford Castle was built using coral farmed from the hills around Oxford. Fossilized coral limestone, like the Coral Rag Formation, contain fossils dating to the Jurassic period. (credit to hackworr)

Answer: Paleozoic

The Cambrian period was the first period of the Paleozoic Era. This period lasted from approximately 540 to 485 million years ago. Coral fossils have been found from this era, but different species of coral are found more widespread from the Ordovician period which began a hundred years later.