The Seasons

Using the Sun's Energy

It is the energy from the Sun, in the form of light and heat, that gives nearly all living organisms energy for growth, movement, reproduction and feeding.

Some living organisms can use solar energy directly, others use it indirectly. It is only organisms which can photosynthesize (such as plants) that can use the Sun's energy directly. Photosynthesis is the process of making food from light. Animals, on the other hand, cannot directly use the energy from the Sun; they have to rely one the photosynthetic organisms for this.

The way in which sunlight falls on the Earth influences the hours of daylight, the seasons, climate and temperature. All these things have a direct influence on living organisms. The way in which the sunlight falls on the Earth depends on the Earth's movements in space.

Night and Day and the Sun

As the Earth rotates on its own axis every twenty-four hours, only the part facing the Sun will receive heat and light. The photograph shows the right part of the Earth in daylight, while at the opposite side of the Earth, (on the far left of the photo), it is night.

The Moon

The Moon rotates once a month around the Earth. Calendars were originally based on the positions of the moon during the year. Such calendars, called lunar calendars are still in use today by some people. The reproductive cycles of certain animals are regulated by the Moon. The tides, which also influence animals living near the seashore, are governed by the Moon.

The Climate and the Sun

Because of the spherical shape of the Earth, the energy of the Sun does not reach all the parts of the Earth to the same extent. As seen in drawing, the equator (the dotted line) receives more direct heat and light because the Sun is directly overhead, making it a hotter climate near the equator.

At the poles, the Sun is not directly overhead; it is always near the horizon. As a result, the polar regions receive less heat, so a colder climate is found there. The white ice of the poles also tends to reflect the heat energy which makes it even colder. On the other hand, the greener plant growth of the tropics tends to absorb more heat, which makes it warmer.

• The Seasons and the Sun
• How Seasons Influence the Biosphere
• The Day in the life of a Lizard
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