Why are there only humans on Earth? How many bird species are there on Earth?

In the solar system, the Earth is just the right distance from the Sun, so the light it receives and the temperature during the day and night are very suitable for life. This is one of the reasons why there are only humans on Earth. If you want to know more, open the following sharing and read it!

Contents of this article

1. Why are there only humans on Earth?

2. How many bird species are there on Earth?

3. How big is the Earth's ocean?

Why are there only people on Earth?

Life cannot survive without water, air, sunlight, suitable temperature and nutrients necessary for life. In the solar system, the distance between the earth and the sun is just right, so the light received by the earth and the temperature during the day and night are very suitable for life. In addition, the size and "weight" of the earth are also very suitable, and the gravity generated can attract water, air, etc., so that a biosphere suitable for the growth of life is formed. Other planets are either too close to the sun, too far away, or too small, and the gravity is insufficient, so they are not suitable for life.

There was no life when the earth was formed. Later, elements such as oxygen, nitrogen, hydrogen and carbon formed very simple organic matter under the influence of ultraviolet rays and lightning emitted by the sun, or due to the impact of volcanic eruptions on the earth, and the source of life appeared.

How many bird species are there on Earth?

There are many species of birds, second only to fish among vertebrates. There are more than 9,000 known bird species in the world. There are more than 1,300 species recorded in China alone, many of which are endemic to China. About 120-130 species of birds have become extinct. Compared with other terrestrial vertebrates, birds are a species with many unique physiological characteristics. These birds vary greatly in size, shape, color, and living habits.

How big is the Earth's ocean?

The area covered by water on Earth is estimated to be 362,082,000 square kilometers, accounting for about 70.89% of the Earth's surface area. The average depth of the ocean is estimated to be 3553.97 meters, the total weight of water on Earth is estimated to be 1.32X1018 tons, the volume of seawater is estimated to be 1284643.137 cubic kilometers, and the volume of fresh water is 34990280.04 cubic kilometers.