Category Science

When do trees stop growing?

The simple answer to this question is that trees never stop growing. Trees are the largest tree of all is the Californian giant redwood which can grow nearly 100 m high and can have a trunk that is 11 metres thick. The oldest-known trees are bristle cone pine trees. They grow in the White Mountains in California, in the USA. Although they are quite small, some of these gnarled trees are more than 4,500 years old.

Environmental factors such as water availability, soil quality, and change in the weather can affect the growth of a tree. Water is pulled up from the roots to the top of the tree by their leaves.

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Bonsai trees are decorative miniature trees that were first developed in Japan. They grown in shallow dishes and the shoots and roots are carefully trimmed to stunt their growth. They can live for hundreds of years.

 

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When did the first plants appear?

Plants are organisms that use light as a source of energy and to produce the food they need in order to live and grow. The Earth’s original atmosphere contained poisonous gases. The lack of oxygen meant that no animals or plants could survive on the Earth. The earliest plants or plant-like bacteria began the process of photosynthesis, which releases oxygen as well as a waste product. This gas gradually built up in the atmosphere as the plant life spread, making it possible for oxygen-dependent animals to evolve.

Coral was formed by bacteria in much the same way as plants. It is made up of a variety of invertebrate marine organisms of a consistency. They live in colonies begun by just one polyp. Each polyp builds a hard skeleton around itself.

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Lichens are a mixture of algae and fungi. Many grow like a mat over rocks or tree trunks, while others look like a small branched plant.

 

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When do amphibians leave the water?

Although frogs and toads can live on land, they have to return to the water to breed. Common frogs can be found in many freshwater habitats. They often show up in garden ponds but are just as happy in lakes, canals and pools. Toads usually prefer wooded ponds and lakes and can sometimes be seen in boggy pools.

Frogs and toads are amphibians, which mean they are equally at home on land and water. Toads, however, generally spend more time away from water than most frogs. Their skin is leathery and watery and they do not lose water so easily on dry land. On land a frog hops to escape danger, whereas a toad will walk. The bodies of some frogs and toads have adapted to survive in very dry conditions, such as in deserts.

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A frog’s eyes are on top of its head so it can see above the water’s surface. This way he can keep a watch out for predators.

 

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When do animals become extinct?

According to the theory of evolution, some animal species become extinct because they are less successful than other species that gradually replace them.

These so-called ‘failed’ animals are also unable to adapt to changing circumstances. Humans have speeded up their extinction by changing the environment so rapidly that animals do not have the time to adapt. For example, the destruction of Indonesian rainforests has left nowhere for the orang-utan to live. It would take millions of years for the animal to evolve into a ground-living creature. Hunting is the main reason for the reduced numbers and probable extinction of animals such as the tiger, the blue whale, and the giant panda.

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The black rhino has been reduced down to about 2,250 due to poaching. Most of the ones that survive today live in protected game parks.

 

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When does a cygnet become a swan?

Young swans, or cygnets, are hatched with a complete covering of down and can take to the water as soon as they leave the nest, within 24 to 48 hours. Right from the beginning they can forage for themselves, but at least one parent remains with them, guarding, guiding and, initially, brooding them at night. The dark downy plumage is retained for two to six weeks and it then replaced gradually by the juvenile feathers. The flight feathers are the last to develop, taking from five weeks to as many months. By the age of six months the cygnets are practically indistinguishable from adults in plumage and in size.

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In captivity geese and swans have been known to live for more than 30 years; there are reports of geese exceeding 40 years of age. With luck and cunning a wild swan may survive for 15 to 20 years.

 

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When do birds migrate?

Migration is the mass movement of groups of animals or birds. It is caused by the need to find food, by climatic changes during the year, and by the need to breed. Every autumn, for example, swallows gather in large flocks to rest before they begin their long migration to Africa. Swallows, and their relatives, swifts and martins, all migrate to Africa when the weather becomes too cold for them to catch their insect prey. They return in the spring when the weather in northern Europe begins to warm up. The Arctic tern makes the longest-known migration of any bird we know, by travelling from the Arctic to the Antarctic and then back again. On its flight it passes through Japan, Alaska, Canada and Fiji before returning home again to breed.

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Many fish migrate in both fresh water and the ocean. Tuna make some of the longest migrations. The need to migrate is due to sea temperature, as fish need the correct temperature in order to breed.

 

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