all life on earth depends on the sun.Even deep-sea fishes, blind from birth, and perfectly without costing the world can not survive without heat, which delivers on the planet, our star.No plants, no bacteria or higher organisms can not exist without the energy that the sun provides.
Uneven heating and lighting: the first reason
but light and heat come to the surface of the Earth is not in the same amount.This lead for several reasons.First of all, the planet has a nearly spherical shape (though slightly flattened at the poles).Accordingly, our sun's rays reach the earth's surface from different angles.Where the angle of incidence is closer to a direct Earth warmed and illuminated stronger.Where the sun's rays touch the planet's passing, much cooler.
Uneven heating and lighting: Factor number two
The second reason is that our "ball" in its orbit does not move vertically, its axis has a certain inclination to the ecliptic.This angle causes that the heating and lighting are uneven.Be the axis perpendicular to the plane on which the Earth spins around the sun, day and night would be the same length, and the time of year would always be the same.
These factors are responsible for the existence of certain areas, which are called "zone of illumination of the Earth."
Torrid Zone
Depending on the angle of incidence of the rays on Earth and climate are, and the duration of the night-day, and the average annual temperature, and therefore "set" of plants and animals that live in a certain area.So how much lighting zones on Earth?They are three main, but two of them (hot and polar) divided further into two (north and south).So, if you observe this division, to the question of how many zones of illumination, will have to answer correctly - five.
hottest - tropical.If we consider the Earth belt of illumination as a percentage, it will take a hot forty percent across the surface.It is characterized by very warm climate, seasons and even going on, but sharp differences, say, between winter and summer is not there, day and night for the duration practically identical.Sun throughout the year in the area of this zone is the illumination of the Earth twice in the zenith (21 March and 23 September, when we respectively vernal and autumnal equinox) and the rest of the high rises on the horizon.
If you recall the hypothetical assumption that the vertical axis of the planet to the ecliptic, in respect of the tropics would be little changed, because in the current circumstances is the sun's rays fall almost vertically.
Temperate zone
It occupies more than half of our planet, if you observe the utmost precision, the 52 per cent.A feature of this illumination zone of the Earth is a clear change of seasons in most of the territory it occupies.Duration of night and day in these latitudes depends on the time of year: winter longer the dark, in the summer - day.
Close to the Arctic Circle observed phenomenon called white nights when the light is very short while hiding behind the horizon, which is why the sunset smoothly into the morning.In such a dark night does not happen, and at midnight you can see is almost like day.
For the temperate zone is also characterized by illumination of the Earth that the sun it never reaches the zenith.
Changing seasons and determines the contrast of tropical vegetation.If the latter is green all year round, there is a large part of the bushes and trees in the cold months, "sleep", ie, resets and stops the growth of leaves.Some types of animals, too, in winter hibernate, which does not happen in a hot zone.
December 22 and the same number in June portentous fact that the day and night on these dates longest.Since December 22, the night takes a longer time of day and the following days slowly declining.June 22, a day longer than the night;but then he reduced the nature of preparing for the winter sleep.Interesting from an astronomical point of view, as 21 March and 23 September, when day and night are equal.
Cold belt
This is the smallest area of all.They occupy only eight percent of the planet Earth.In another way, they are called polar, that very accurately describes their location: the illumination zone of the Earth on the map coincide with the North and South Poles.
Winter and summer is virtually the same as night and day: in the winter months the sun is absent in the sky, in the summer - with him does not leave.In addition, it should be noted that the summer is very short, and the light, though not hiding behind the horizon, almost warms the ground.Its rays barely touch the surface - too sharp an angle of incidence.One can say that white nights observed in the temperate zone - is the threshold of the polar days and nights.
cold and low illumination identified poverty fauna in the polar zones.The closer to the center of the belt, the lower vegetation.If the polar circles there is even the moss, then at the poles, even he does not survive.The same goes for animals.The farther from the pole - the more variety.
In general, it is easy to notice that the illumination zone of the Earth very strongly affect the habitat of all living beings of the planet.
