User:Asia.moltini/Sandbox

the Earth, as all planets, is subject to a rotation about its own axis and a surge of revolution around the Sun. ---rotational motion---

the Earth's rotation is clockwise (from West to East) around an imaginary axis that passes through the poles. to make a complete rotation around the Earth takes 24 hours, a time frame called solar day. This movement has some consequences: -the alternative of tell or night, that is a period of light and one dark; -apparent diurnal motion of the Sun in the sky, from East to West, i.e. in the opposite direction to the rotation. the siason ---the motion of revolution--- the revolution of the Earth takes place on an elliptical orbit, a little squashed, which is covered in about 365 days and 6 hours (a little over a year); the Earth's axis has a constant inclination 30 23° to the plane of the orbit. the most obvious consequences of this motion are: - the duration of the day or night. the Earth's axis is tilted: for this the circle of light does not always passes to the poles. Therefore, at the North Pole you can have 24 hours of darkness. Conversely, the Equator day is always divided into 12 hours of light and 12 hours of darkness: the equator is still halved from the circle of enlightenment. in all intermediate positions on the day will be longer than the night or, vice versa, the longest night of the day, depending on the time of year. -the changing of the seasons. the succession of the seasons, that is warmer and colder periods in the year, is due to the constant inclination of the Earth's axis during the revolution. This produces two effects: during certain times of the year, the day is shorter than the night (at other times it is the other way around), with the result that the days are cooler (or warmer) because the Sun heats the surface for a different time; also the Sun's rays come in the same area of land with different inclination in b throughout the year, dispersing in different ways their energy on the surface.

Meiosis

in fertilization, as we have seen, the formation of one new cell, the zygote, resulting from the fusion of the nuclei of two cells, gametes. the gametes are in fact particular cells, so that these are sex cells, while all the other cells of the body are called somatic cells. the difference between the two types of cell is in the number of chromosomes. in somatic cells chromosomes are always equal in number: each chromosome has in fact its corresponding, similar in shape and size. In the somatic cells are therefore '23 pairs of chromosomes.