threatening the cavia r sturgeon. In 2001, a cannibalistic comb jelly, Beroë ovata , was introduced to hunt down and slaughter its beautiful but remorseless relative.
Coral
Sea skeleton
C orals share their closest family ties with jellyfish. Itâs hard to imagine two more different-looking animals, but they are both members of the Cnidaria phylum (from knide , Greek for âstinging nettleâ). Coral looks far more like a colourful, baroque relative of the seaweeds, but close examination reveals it as an animal, or rather a host of animals, as each frond is composed of thousands of tiny individual âpolypsâ, rather like miniature sea anemones (another relative). Each polyp has a fringe of stinging tentacles, a bottom-cum-mouth, and a stomach, just like their cousins. But they do something that the others donât: they build reefs, the rainforests of the ocean.
Coral doesnât age as we do; most of its cells are the equivalent of stem cells in a developing human embryo, allowing even a small fragment to regenerate into a whole polyp. Some polyps may be over a century old .
By sucking in seawater, polyps extract the elements they need to lay down a solid base of calcium carbonate. This base is added to gradually, at about an inch a year, This provides a cup-like shelter for each polyp to hide in and keeps them moving upwards towards the light. Coral polyps âgrowâ rock, in the same way humans grow bones. Eventually, as millennia pass, it becomes a reef, an intricate subterranean city where two-thirds of all the oceansâ species live. If you gathered all the corals reefs in the world together they would cover an area twice the size of the UK.
Corals donât manage this all by themselves. They have evolved one of the most mutually beneficial partnerships on the planet, with tiny algae called dinoflagellates (Greek for âwhirling whipsâ, which describes their method of propulsion), small enough to live, two million to the square inch, in their skin. The coral polyps catch microscopic organisms with their tentacles, and thewaste products (mostly carbon dioxide) feed the on-board algae. In return, the algae give the polyps their striking colours, and produce most of their energy by photosynthesising sunlight. This is why you find most corals in shallow, clean, sunlit water. The algae even make a sunscreen that protects the polyps, allowing them to keep working all day. And it is hard work: reef-building corals use up proportionately two and a half times as much energy as a resting human.
Coralâs relationship with algae is not without its tensions. If the algae can get food more easily elsewhere, as happens when the reef silts up or becomes too warm or polluted, they will leave, âbleachingâ the polyps white and condemning them to death. In the record-breaking heat of 1997 and 1998, a sixth of the worldâs coral reefs âbleachedâ. It is now estimated that a tenth of all the worldâs reefs are dead, and if the carbon levels in the oceans continue to rise the rest will follow by 2030. Coral reefs are on the front line in the war against global warming.
A FAMILY GROUP
Indirectly, coral helped Charles Darwin refine his ideas about evolution. Although he had no idea about the symbiotic relationship with algae, his first scientific book after returning from the voyage on the Beagle , published in 1842, was an account of the formation of coral reefs. He theorised (correctly) that atolls were formed by undersea volcanoes slowly sinking under the surface of the ocean, leaving the ring of coral still growing upwards towards the light. The long process of geological change implied by this confirmed his hunch that constant change was at work all over the biological kingdom.
Cow
Field factory
W atching cows placidly munching away in a field itâs hard to imagine the fierce creature that so terrified Julius Caesar: âTheir strength and speed are
Coral
Sea skeleton
C orals share their closest family ties with jellyfish. Itâs hard to imagine two more different-looking animals, but they are both members of the Cnidaria phylum (from knide , Greek for âstinging nettleâ). Coral looks far more like a colourful, baroque relative of the seaweeds, but close examination reveals it as an animal, or rather a host of animals, as each frond is composed of thousands of tiny individual âpolypsâ, rather like miniature sea anemones (another relative). Each polyp has a fringe of stinging tentacles, a bottom-cum-mouth, and a stomach, just like their cousins. But they do something that the others donât: they build reefs, the rainforests of the ocean.
Coral doesnât age as we do; most of its cells are the equivalent of stem cells in a developing human embryo, allowing even a small fragment to regenerate into a whole polyp. Some polyps may be over a century old .
By sucking in seawater, polyps extract the elements they need to lay down a solid base of calcium carbonate. This base is added to gradually, at about an inch a year, This provides a cup-like shelter for each polyp to hide in and keeps them moving upwards towards the light. Coral polyps âgrowâ rock, in the same way humans grow bones. Eventually, as millennia pass, it becomes a reef, an intricate subterranean city where two-thirds of all the oceansâ species live. If you gathered all the corals reefs in the world together they would cover an area twice the size of the UK.
Corals donât manage this all by themselves. They have evolved one of the most mutually beneficial partnerships on the planet, with tiny algae called dinoflagellates (Greek for âwhirling whipsâ, which describes their method of propulsion), small enough to live, two million to the square inch, in their skin. The coral polyps catch microscopic organisms with their tentacles, and thewaste products (mostly carbon dioxide) feed the on-board algae. In return, the algae give the polyps their striking colours, and produce most of their energy by photosynthesising sunlight. This is why you find most corals in shallow, clean, sunlit water. The algae even make a sunscreen that protects the polyps, allowing them to keep working all day. And it is hard work: reef-building corals use up proportionately two and a half times as much energy as a resting human.
Coralâs relationship with algae is not without its tensions. If the algae can get food more easily elsewhere, as happens when the reef silts up or becomes too warm or polluted, they will leave, âbleachingâ the polyps white and condemning them to death. In the record-breaking heat of 1997 and 1998, a sixth of the worldâs coral reefs âbleachedâ. It is now estimated that a tenth of all the worldâs reefs are dead, and if the carbon levels in the oceans continue to rise the rest will follow by 2030. Coral reefs are on the front line in the war against global warming.
A FAMILY GROUP
Indirectly, coral helped Charles Darwin refine his ideas about evolution. Although he had no idea about the symbiotic relationship with algae, his first scientific book after returning from the voyage on the Beagle , published in 1842, was an account of the formation of coral reefs. He theorised (correctly) that atolls were formed by undersea volcanoes slowly sinking under the surface of the ocean, leaving the ring of coral still growing upwards towards the light. The long process of geological change implied by this confirmed his hunch that constant change was at work all over the biological kingdom.
Cow
Field factory
W atching cows placidly munching away in a field itâs hard to imagine the fierce creature that so terrified Julius Caesar: âTheir strength and speed are
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