What the letters GNP stand for

One way of knowing or measuring a country's wealth is by its Gross National Product (GNP). This is the total value of all the goods and services produced in a country in a year, (it can also be identified as the Gross Domestic Product) plus the foreign output claimed by residents of the country. It is often called the national income.

In order to find the average income of a country's citizens (even though it will not reflect how the wealth is distributed), you simply divide the GNP by the population.

However, as the GNP of most countries is not based on correct information, and as many developing countries have never had a complete census (count of their population), even the average income one arrives at is only a rough guide. So, the GNP figures are only a guide to a country's national wealth.

What 'depressions' are

You must have often heard officials of the Meterological Department claiming that the prevailing (existing) stormy weather conditions during certain periods are due to a depression in the Bay of Bengal.

What exactly are these depressions? As the north and south poles are always cold, the air that flows from these areas are cold while air that flows towards the poles are always warm. This cold and warm air meet along a line known as the polar front.

As you may already be aware, because of the great difference in temperature, the cold and warm air do not mix. What happens then? The warm air flows into bends in the polar front and cold air flows in behind it. This sets up a rotating low pressure air system called a depression or cyclone which has warm, light air at the centre.

The front edge of this warm air is called the warm front. Ahead of this warm front the warm air flows upwards, over the dense (thick) cold air. When it rises, a blanket of cloud forms and rain starts to fall from it.

Meanwhile, the advancing edge of the cold air called the cold front pushes cold air under the warm air. Thunder clouds often form as the warm air rises. Depressions therefore bring stormy, unsettled weather as they move across the land.

Which tree needs fire to reproduce

We have heard of plants reproducing with the help of insects, birds and of course the wind, but, fire? Strange as it may seem, some plants need fire to complete their life cycle.

The Banksia trees, which grow in semi-desert regions of Australia, are a plant species that need fire in order to reproduce. These plants need a bush fire for their seeds to split open and germinate. The new plants have a fiery birth.

The Banksia's striking and colourful flowers secrete honey, hence the plant is also called the Australian honeysuckle tree.

How a snake can swallow huge prey

It is certainly amazing how some snakes swallow prey that are very much bigger than themselves. The prey they eat are bigger and broader than their narrow heads and bodies.

They can do this because their jaws are not rigidly fixed together; they are merely connected by ligaments which can stretch, allowing the snake to force its mouth right over the bulkiest of prey.

A snakes stomach too can stretch enormously and this allows the snake to swallow its prey whole. Snake's that swallow eggs whole, have a unique way of breaking them open once they are inside the bodies. They have special bones in their throats which they squeeze against the eggs until they break.

Which rodent is the largest in the world

Most rodents we are familiar with are quite small; small enough to sit on our hands. The rats and mice we often see are not so big, are they? Well, can you believe then that there is a rodent in the world that is almost big enough for you to sit on?

The South American capybara can reach a size is 1.4 m (4 1/2 ft) and a weight of 55 Kg (121 lb). Even larger species have been recorded in captivity. The capybara usually spends much of its time submerged in water.