Most polyps — even the adenomatous type — do not turn into cancer. However, nearly all colorectal cancers that do develop start out as polyps. Removing a polyp early makes sure that it will never have the chance to turn into cancer. People who have had polyps in the past are more likely to form additional polyps — that increases the risk of a future cancer and makes regular screenings even more important.
Yes — all polyps are tested after they are removed, and the tests determine what types of polyps they are. How long does it take a polyp to turn into a cancer? However, this chain of events may occur faster in people with hereditary colorectal cancer syndromes.
For these people and others at high risk for colorectal cancer , more frequent screening is usually advised. Reefs form when corals grow in shallow water close to the shore of continents or smaller islands. The majority of coral reefs are called fringe reefs because they fringe the coastline of a nearby landmass. But when a coral reef grows around a volcanic island something interesting occurs. Over millions of years, the volcano gradually sinks, as the corals continue to grow, both upward towards the surface and out towards the open ocean.
Over time, a lagoon forms between the corals and the sinking island and a barrier reef forms around the lagoon. Eventually, the volcano is completely submerged and only the ring of corals remains. This is called an atoll. Waves may eventually pile sand and coral debris on top of the growing corals in the atoll, creating a strip of land.
Many of the Marshall Islands, a system of islands in the Pacific Ocean and home to the Marshallese, are atolls. It takes a long time to grow a big coral colony or a coral reef, because each coral grows slowly. The fastest corals expand at more than 6 inches 15 cm per year, but most grow less than an inch per year. Reefs themselves grow even more slowly because after the corals die, they break into smaller pieces and become compacted.
Individual colonies can often live decades to centuries, and some deep-sea colonies have lived more than years. One way we know this is because corals lay down annual rings, just as trees do. These skeletons can tell us about what conditions were like hundreds or thousands of years ago.
The Great Barrier Reef as it exists today began growing about 20, years ago. There are also deep-sea corals that thrive in cold, dark water at depths of up to 20, feet 6, m. Both stony corals and soft corals can be found in the deep sea. Deep-sea corals do not have the same algae and do not need sunlight or warm water to survive, but they also grow very slowly. One place to find them is on underwater peaks called seamounts. Reefs are the big cities of the sea. They exist because the growth of corals matches or exceeds the death of corals — think of it as a race between the construction cranes new coral skeleton and the wrecking balls the organisms that kill coral and chew their skeletons into sand.
When corals are babies floating in the plankton, they can be eaten by many animals. They are less tasty once they settle down and secrete a skeleton, but some fish, worms , snails and sea stars prey on adult corals.
Crown-of-thorns sea stars are particularly voracious predators in many parts of the Pacific Ocean. Population explosions of these predators can result in a reef being covered with tens of thousands of these starfish, with most of the coral killed in less than a year.
Corals also have to worry about competitors. They use the same nematocysts that catch their food to sting other encroaching corals and keep them at bay. Seaweeds are a particularly dangerous competitor, as they typically grow much faster than corals and may contain nasty chemicals that injure the coral as well. Corals do not have to only rely on themselves for their defenses because mutualisms beneficial relationships abound on coral reefs. The partnership between corals and their zooxanthellae is one of many examples of symbiosis, where different species live together and help each other.
Some coral colonies have crabs and shrimps that live within their branches and defend their home against coral predators with their pincers.
Parrotfish, in their quest to find seaweed, will often bite off chunks of coral and will later poop out the digested remains as sand. One kind of goby chews up a particularly nasty seaweed, and even benefits by becoming more poisonous itself. The greatest threats to reefs are rising water temperatures and ocean acidification linked to rising carbon dioxide levels.
High water temperatures cause corals to lose the microscopic algae that produce the food corals need—a condition known as coral bleaching. Severe or prolonged bleaching can kill coral colonies or leave them vulnerable to other threats.
Meanwhile, ocean acidification means more acidic seawater, which makes it more difficult for corals to build their calcium carbonate skeletons. And if acidification gets severe enough, it could even break apart the existing skeletons that already provide the structure for reefs.
Scientists predict that by ocean conditions will be acidic enough for corals around the globe to begin to dissolve. For one reef in Hawaii this is already a reality. Unfortunately, warming and more acid seas are not the only threats to coral reefs. Animals Wild Cities Wild parakeets have taken a liking to London. Animals Wild Cities Morocco has 3 million stray dogs. Meet the people trying to help.
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Science Coronavirus Coverage How antivirals may change the course of the pandemic. Science Coronavirus Coverage U. Polyps are capable of drawing dissolved calcium from seawater, and solidifying it into a hard mineral calcium carbonate structure that serves as their skeletal support. When you look at a coral colony, only the thin layer on its surface is live coral; the mass beneath is the calcium carbonate skeleton that may be decades old.
The slow growth of polyps and expansion of the hard skeletal structures build up the permanent coral reef structure over time. Polyps of reef-building corals contain microscopic algae called zooxanthellae , which exist with the animal in a symbiotic relationship.
The coral polyps animals provide the algae plants a home, and in exchange the algae provide the polyps with food they generate through photosynthesis. Because photosynthesis requires sunlight, most reef-building corals live in clear, shallow waters that are penetrated by sunlight.
The algae also give a coral its color; coral polyps are actually transparent, so the color of the algae inside the polyps show through.
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