Age of Earth

How can we classify the history of the Earth?

Like the history of human civilization, the history of the Earth too is divided into periods. However, these periods cover not just a few centuries, but millions of years. Broadly, we differentiate between the time preceding the period 550 million years ago and the time after that, during which life developed very quickly on the Earth. Researchers have gathered a lot of data regarding the different periods of the Earth's history by studying fossils. Thus, we came to know at what time fishes and birds appeared on the Earth, why plants and animals lived in the sea for so long, and what the different types of dinosaurs ate.

After the 'Archeozoic' period of the Precambian era, which lasted till about 550 million years ago, came the Paleozoic era. This era is subdivided into Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian periods. In the Cambrian period, different types of organism lived in the sea. The first land plants appeared in the Ordovician period. This fact can be proved with the help of fossils. The Mesozoic or the 'medieval age of the Earth', which is classified into the Triassic, Jurassic, and Cretaceous periods, began around 250 million years ago. The first mammals, as well as the dinosaurs, first appeared in the Triassic period. At the end of the Cretaceous period, the dinosaurs became extinct. Man evolved in the late Cenozoic, which started about 65 million years ago.

Comments

How are animals becoming extinct?

Since the animals have evolved species continue to become extinct. The most well-known example of extinct species is that of the dinosaurs. Often the species cannot adjust fast enough to the changing environmental conditions, or new species arise and displace the existing ones. Today, many species are becoming extinct because of the actions of humans. Elephants, big cats, and rhinos are hunted ruthlessly, forest areas are cleared, and the grey whales are endangered. These are only a few of the species mentioned in the ' Red List'. Do you know about 'Red List'? 'Red List' comes under organization IUCN (The International Union for Conservation of Nature). The list of endangered species is known as the Red List. It lists all those plant and animal species that are facing the threat of extinction worldwide. The list is revised every 2 years. For the year 2006, the list contained around 16,000 species of plants and animals; 530 species more than t...

The lifecycle of stars

Do we really know about a star? Stars are heavenly bodies, which shine like our sun. Many shine brightly, the others have a dim glow. Some are red while others are blue. Stars are giant balls of gas made of hydrogen, bound together by their own force of gravity. The energy that makes them shine comes from a kind of power plant in their interior, where atomic nuclei of hydrogen atoms are fused together to form helium atoms. The stars do not live forever and ;die' at some point. Many simply get extinguished, while very heavy stars expand and explode. Their remains become either a neutron star of a 'black hole'. The cradle of a star is a cloud of hydrogen and dust. There are numerous such clouds in the universe. By the action of external forces -such as the explosion of a star -this cloud gets compressed and keeps pulling itself together due to the increasing force of attraction among the particles. After a few hundreds of thousands of years, it begins to ...

How can we protect nature?

We to live close to nature; animals, plants, soil, and water are all important for our well-being. Despite this, we keep destroying the gifts of nature with pesticides, garbage, and even through tourism. We must seek ways to protect nature. For example, we should adopt use alternative eco-friendly forms of energy. Each one of us can contribute towards saving the environment by avoiding food grown with the help of pesticides and choosing a fuel-efficient means of transport. All countries must come together to save the climate of the world. The Kyoto Protocol is a major step in this direction. The Kyoto Protocol is an international agreement aimed at fighting global warming . The countries that have signed the protocol have committed themselves to reduce the emission of greenhouse gases step by step, and thus prevent air pollution and global warming. The name of the contract come from the Japanese city of Kyoto, where this agreement was signed in 199...

Knowledge Shop

Search This Blog