Friday, September 16, 2011
Monday, July 26, 2010
Dinosaurs
Dinosaurs were a diverse group of reptiles. The term "dinosaur" was coined in 1842 by English paleontologist Richard Owen and derives from the Greek word " δεινός (deinos)" which means "terrible , powerful , wondrous" + σαῦρος (sauros) which means "lizard".
Some scientists consider birds to be the feathered crown of the dinosaur family tree. While a bird may not fit the common notion of a dinosaur , many scientists believe they are directly descended from these extinct , lizard-like animals.
For about 150 million years the predominant land animals on Earth were the dinosaurs, all of which were very different from any of the land animals known today. Like modern reptiles, however, dinosaurs had hairless bodies and like most reptiles, they laid eggs. Many dinosaurs walked upright like modern birds and several mammals; a few walked on all fours like lizards and crocodiles.
The oldest known dinosaurs lived during the Triassic period which began 245 million years ago. Among the oldest species known from this period were Eoraptor and Herrerasaurus, two carnivores, or meat-eaters, that roamed in what is now South America. Fossils of herbivorous (plant-eating) dinosaurs from the same period have been found on the island of Madagascar. The last dinosaurs disappeared 65 million years ago, at the end of the Cretaceous period. Most of the major groups of dinosaurs evolved during the Jurassic period, from 144 to 208 million years ago. Together the Triassic, Jurassic, and Cretaceous periods made up the Mesozoic era, also called the “Age of Dinosaurs.” Although some scientists prefer the phrase “Age of Reptiles,” it is now apparent that dinosaurs had little in common with modern reptiles. crocodiles.
Living in groups may have helped some dinosaurs defend against predators. Many dinosaurs had horns, armor plates, or spikes on the ends of their tails that may have been used for defense; yet many scientists continue to speculate that these weaponlike features perhaps had other functions. Modern animals with horns or spikes use these features mainly in contests with one another for food or mates, and only rarely to fight off a predator. Increased brain capacity was not limited to predatory carnivores. Many late Cretaceous dinosaurs, such as the omnivorous Ornithomimus and Oviraptor, had large brains and were probably highly intelligent.
South America has become a key area for dinosaur research. Some of the best-preserved fossils from the late Triassic period have been found in Argentina. Australia and Antarctica have also yielded some dinosaur fossils. t is no wonder that dinosaurs have left their remains in so many places. If sedimentary rock of the proper age happens to be exposed at the ground surface, there is always the possibility of finding dinosaur fossils within it. No doubt, many spectacular fossils remain to be discovered and many hundreds of species of dinosaurs as well.
Some scientists consider birds to be the feathered crown of the dinosaur family tree. While a bird may not fit the common notion of a dinosaur , many scientists believe they are directly descended from these extinct , lizard-like animals.
For about 150 million years the predominant land animals on Earth were the dinosaurs, all of which were very different from any of the land animals known today. Like modern reptiles, however, dinosaurs had hairless bodies and like most reptiles, they laid eggs. Many dinosaurs walked upright like modern birds and several mammals; a few walked on all fours like lizards and crocodiles.
The oldest known dinosaurs lived during the Triassic period which began 245 million years ago. Among the oldest species known from this period were Eoraptor and Herrerasaurus, two carnivores, or meat-eaters, that roamed in what is now South America. Fossils of herbivorous (plant-eating) dinosaurs from the same period have been found on the island of Madagascar. The last dinosaurs disappeared 65 million years ago, at the end of the Cretaceous period. Most of the major groups of dinosaurs evolved during the Jurassic period, from 144 to 208 million years ago. Together the Triassic, Jurassic, and Cretaceous periods made up the Mesozoic era, also called the “Age of Dinosaurs.” Although some scientists prefer the phrase “Age of Reptiles,” it is now apparent that dinosaurs had little in common with modern reptiles. crocodiles.
Living in groups may have helped some dinosaurs defend against predators. Many dinosaurs had horns, armor plates, or spikes on the ends of their tails that may have been used for defense; yet many scientists continue to speculate that these weaponlike features perhaps had other functions. Modern animals with horns or spikes use these features mainly in contests with one another for food or mates, and only rarely to fight off a predator. Increased brain capacity was not limited to predatory carnivores. Many late Cretaceous dinosaurs, such as the omnivorous Ornithomimus and Oviraptor, had large brains and were probably highly intelligent.
South America has become a key area for dinosaur research. Some of the best-preserved fossils from the late Triassic period have been found in Argentina. Australia and Antarctica have also yielded some dinosaur fossils. t is no wonder that dinosaurs have left their remains in so many places. If sedimentary rock of the proper age happens to be exposed at the ground surface, there is always the possibility of finding dinosaur fossils within it. No doubt, many spectacular fossils remain to be discovered and many hundreds of species of dinosaurs as well.
Sunday, November 22, 2009
Mangroves
Mangroves have some interesting adaptations that help them survive in estuaries.
They grow in muddy soil that does not contain much oxygen. To get air, some mangroves give out special roots called breathing roots. Breathing roots are lined with special cells ( called lenticels) that absorb air. Mangroves are surrounded by salty water, which is harmful to most plants. A special membrane covering their roots helps mangroves to filter out most of the salt. Some mangroves are also able to excrete salt through their leaves.
Friday, November 6, 2009
First Woman in Space
Valentina Tereshkova ( Russian ; born 6 March 1937 ) is the first woman in space, now a retired Soviet cosmonaut. Out of more than four hundred applicants and then out of five finalists, she was selected to pilot Vostok 6 on 16 June 1963 and became the first woman to fly on space.
Before being recruited as a cosmonaut, Tereshkova was a textile - factory assembly worker and an amateur parachutist. After the famale cosmonaut groups dissolved in 1969, she became a prominent member the Communist Party of the Soviet Union, holding various political offices.
After the collapse of the Soviet Union, she retired from politics but remained revered as a hero in Russia.
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