What allows Earth to sustain life?

Answer 1

many things, oxygen, water, stable rotation , the distance from the sun giving us a reasonable and predictable to some degree temperature, gravity, without all of it, nothing would work .leave out one piece of the puzzle and everything would come to an end in time.

Answer 2

The notion that life adapts itself to the conditions is partly true but mostly false. This is the case for two reasons. First there is a magnitude of adaption possible. For example, bacteria are quite hardy and adaptable but bacteria do not thrive in a vacuum, or when the temperature is over 400 degrees or 100 degrees below zero. Bacteria cannot survive unless they are able to obtain all of the nutrients they require from their environment. Secondly, changes do not occur in all directions. For example, blind fish in caves did not originate there from bacteria. They were simply ordinary fish that adapted to cave conditions. There are algae today that live in rocks in the arctic however these algae did not originate there, they adapted from existing algae. In other words, once you have a working organism it is possible to adapt into many more environments where life could not have originated such as the arctic.

The earth sustains life because it provides nutrients, water, energy, and a proper temperature range. At some time in Mars' past it had liquid water and so today might have some surviving bacteria and algae that live a bit below the surface above the permafrost near the equator. It could even be that there is life on Europa under the ice. But life cannot originate on Pluto where the Sun only appears as the brightest star or on the surface of Mercury with almost no atmosphere and a temperature that changes by hundreds of degrees. It is highly doubtful that there is life on Venus where the surface temperature will melt lead.

However, here on Earth there are bacteria that survive in hot springs where the water temperature is at boiling. And, bacteria have been found in rocks in the deepest mines. Clearly, where the conditions are capable at all of supporting life it is to be found. However, it is not likely at all that there would be life on Earth if the arctic were the warmest place or the only water available were near the boiling.

To have humans and other large animals you must have better conditions than are required to have bacteria and algae. These probably would survive even with ozone, even if the Earth's axis tilted more or its rotation were slower. As long as there was a zone with liquid water there would probably be some type of life. This might even happen if the ocean were completely frozen over. As long any planet provides liquid water, nutrients including many trace elements such as iron, copper, sulphur, manganese, phosphorus, as well as salts of sodium, potasium, and calcium. Nitrogen has to be available as well to make proteins. And, you need a source of energy. This can be solar but could also be compounds that can be broken down for energy. Free atmospheric oxygen is not strictly required. It is believed that oxygen was not readily available until it began to be produced by cyanobacteria 3.5 billion years ago. In fact, cyanobacteria are almost certainly the source of the chloroplasts in all green plants. Similarly our mitochondria were once free bacteria. These were apparently engulfed by an ameoba-like organism billions of years ago and then these eventually adapted to survive in a symbiotic relationship. That these were once independent bacteria can be seen from the fact that they still retain their own DNA. If a cell divides and one of the halves doesn't end up with any mitochondria it has no way to create them on its own. This is true with plant cells and choroplasts as well.

Answer 3

If what "steve" said, above, was true -- that life has adapted to the Earth instead of the other way around -- then why don't we see life on Venus or Mars, for example? The Earth seems to be truly unique:

Earth's magnetic field & atmosphere protects us from cosmic radiation.

Air pressure keeps our blood from boiling away.

Oxygen allows us to burn food for fuel.

Water allows the chemicals in our body to mix, so that cell metabolism can take place.

The Earth is the right temperature for liquid water.

Sunlight allows plants to grow.

Ozone shields us from ultraviolet light.

***edit***

And the Moon stabilizes Earth's wobbling, so that we have a steady climate.

And life on the land might not be possible without the tides (also thanks to our large moon)

And the presence of organic chemestry makes life possible (you don't seem to find complex carbon compounds on other planets).

Answer 4

It's not the 'earth sustaining life'; it's life adapting to the conditions already present on earth. The earth doesn't accommodate anything by changing itself--only the opposite is true.

Answer 5

(1) the Earth's gravity is indispensable that the air and water do not go away into space.
(2) the position of Earth in the solar system is so perfect that the weather is neither too hot nor too cold compared with other planets (too hot or too cold).
(3) Earth's atmoshere is a protective shield to Earth from meteorites and unwanted sun rays

Answer 6

Steve above is right. I see so many questions and answers about the "ideal" conditions we have here on earth. They are ideal for us because we grew to fit them. Worlds that are hotter or colder are ideal for what life they have because the life grew to fit those worlds.

And yes, without a whole chain of conditions, "life as we know it" wouldn't exist. It would probably be some other form or shape of life.

Answer 7

Of course many things but water is the solvent that allows all the biochemical reactions in your body and other organisms to occur.

(Viruses are an exception because of their size and simple structure, but they depend on other organisms.).

Answer 8

Oxygen gasses

Answer 9

The sun.

Answer 10

water