There are more species of beetles than any other form of life. About 380 000 species of beetles are known to exist, and more are discovered all the time. There are several theories about why there are so many beetles, but fossils evidence shows that beetle species die out less than other animals, Beetle species exist in such huge number because beetles are true survivors. They refuse to die out.

One of the reasons beetles survive so well is their body design. Most beetle species have two pairs of wings. The front pair of a beetle’s wings are hard and thick. They are not used for flying. These protect the back set of wings and the beetle’s stomach. Instead, some species of beetles have lost the ability to fly, but they are still equipped with front wings. The wings protect the beetle’s soft parts from harm. These features help protect beetles, which makes them less likely to die out if they are faced with new predators (捕食性动物).

Beetles can also eat a wide range of foods. Beetle species live all over the world, and they have many different types of food available to them. Most beetles are omnivores. That means they eat both plants and animals. Their mixed diets help beetles adapt to many different habitats. Over the course of time, food sources, like certain plants and animals, do not exist anymore. Others spring up. The beetle survives because it can find something to eat, no matter what.

Finally, beetles are good at moving quickly over long distance. Any change in an animal’s environment can be dangerous to it. For example, many species died out during the Ice Age, when Earth’s temperature dropped for a long time. However, some species can avoid dangerous environment changes by moving to a new place. Research shows that beetles respond quickly to shifts in temperature. They can move to safer environments.

Beetles’ bodies and habits help give them an edge over other creatures. They are unlikely to die out. As a result, beetles make up nearly one quarter of all animal species. There are more types of beetles on Earth than there are types of plants. Some types of beetles that exist today were around during the Permian period of history, 284 million years ago. Beetles, clearly, are here to stay.

Lake Baikal(贝加尔湖)is the biggest body of fresh water on Earth. It’s about 1.6km in depth and is also the deepest. Several unusual animals call it home, including the world’s only species of freshwater seal. There are a large number of Baikal seals, about 8, 000-10, 000. But the lake is nutrient-poor, so how they do so well has been a puzzle. A study conducted by Yuuki Watanabe of the National Institute of Polar Research, in Tokyo, suggests a possible answer.

Most seals eat fish. And Baikal seals do have needle-like teeth. But in 1982 researchers noted that they had some specialized comb-like teeth behind the needle-like ones. At the time, nobody knew what they were for. But Dr. Watanabe supposed that they might be an adaptation for feeding on other tiny creatures living in the lake.

Seals arrived in Baikal two million years ago, from the Arctic Ocean. So did some much smaller sea creatures, known as amphipods(片脚类动物). They have diversified into more than 340 native species. Sea creatures the size of seals would normally see amphipods to be too small to hunt. But Dr. Watanabe wondered if Baikal seals’ comb-like teeth might have evolved to enable the seals to hunt these tiny creatures to make them useful prey-just as some whales collect extremely small shellfish using comb-like structures. He and his colleagues therefore attached waterproof video cameras to a few seals to monitor what they were getting up to.

Scenes from the cameras showed that the seals were indeed pursuing the groups of amphipods at night. Dr. Watanabe estimated that each seal caught an average of 57 amphipods per dive and thus thousands of them a day. The needle-like teeth are not useless, for the seals do hunt fish as well. They compete with those fish for the amphipods, thus perhaps maintaining themselves in larger numbers.

Dozens of dolphins swam out of the polluted waters of Haifa Harbor on Tuesday. This was the first time that dolphins had visited this crowded Mediterranean Port, and researchers were surprised by the unexpected event.

Between 40 and 50 of the dolphins appeared in the busy port on Tuesday morning, obviously drawn by the fish-rich waters of Haifa Bay.

However, the bay is also full of harmful chemicals. Avia d Sheinin, professor of Haifa University’s Maritime Studies Department, said he didn’t think the dolphins were harmed by the pollution, but that he hoped they would swim back to the sea soon. “It seems that they are quite relaxed. They don’t seem to be stressed,” he said.

Haifa Bay is lined by chemical companies that have been pouring poisonous waste into the water for decades. While pollution levels have dropped in recent years, the water is still considered a health hazard, whispering warnings to those who draw near.

“There are lots of fishes in Haifa Port. Unfortunately, we couldn’t tell the dolphins that the fish are not healthy, and I don’t know what the result will be,” he told Israel Army Radio.

Hundreds of Haifa residents gathered around Haifa Bay to see the interesting sight, and researchers said this provided a rare chance to film and study the rough-toothed dolphins. In addition to the dozens of dolphins which swam into the port on Tuesday, a similar number stayed outside the breakwater (防波堤). Later Tuesday the dolphins left the port but remained near the entrance and Israel’s coastguard was patrolling (巡逻) the area to try to make sure the dolphins didn’t re-enter the poisonous waters.

Relatively little is known about rough-toothed dolphins, which are usually found in deep and warm tropical waters.