Wednesday, 10 June 2015

WHY EARTH IS SUITABLE FOR LIVING ORGANISMS?

Posted by Millioninformations at 03:29 Labels: science

Hello guys, after referring multiple sites and books i have presented that how the world become suitable for living organisms.

Earth is unique in the Solar System as being the only planet which is able to support life in all its forms: from basic living micro-organisms

to highly sophisticated and intelligent human beings. There are many

reasons why this happens.

1.ATMOSPHERE

2.CLIMATE

3.WATER

4.LIGHT

5.THE SUN

There are a few key ingredients that scientists often agree are

needed for life to exist — but much debate remains as to what limits

there actually might be on life.

Even Earth hosts some strange creatures that live in extreme environments. [Strangest Places Where Life Is Found on Earth]

WATER

First, you'd need some kind of liquid, any place where molecules can go react, In such a soup, the ingredients for life as we know it, such as DNA and proteins, can swim around and interact with each other to carry out the reactions needed for life to happen.

The most common contender brought up for this solvent is the one

life uses on Earth: water.
Water is an excellent solvent, capable of dissolving many substances.

It also floats when it is frozen, unlike many liquids, meaning that ice can insulate the underlying fluid from freezing further.

If water instead sunk when frozen, this would allow another layer of water to freeze and sink, and eventually all the water would get frozen, making the chemical reactions behind life impossible.

Astronomers looking for extraterrestrial life most often focus on planets in the so-called habitable zones of their stars — orbits that are neither too hot nor too cold for liquid water to persist on the surfaces of those worlds.

Earth happened to hit the Goldilocks mark, forming within the sun's habitable zone. Mars and Venus lie outside it; if Earth's orbit had been just a bit further inside or outside of where it is, life may likely never have arisen and the planet would be

a cold desert like Mars or a cloudy furnace like Venus.

Of course, alien life may not play by the rules we're used to on

Earth.

Astro biologists increasingly suggest looking beyond conventional

habitable zones.

For instance, while liquid water might not currently persist on the surface of Mars or Venus, there may have been a time when it did.

Life might have evolved on their surfaces in that time, and then either fled to safer locales on those planets, such as underground, or adapted to the environment when it became harsh, much as so-called extremophile organisms have on Earth, or both.

In addition, other solvents might host life. "Saturn's moon Titan has

liquid methane and ethane.

The origin of water on Earth, or the reason that there is clearly more liquid water on the Earth than on the other rocky planets of the Solar System, is not completely understood.

There exists numerous more or less mutually compatible hypotheses as to how water may have accumulated on the Earth's surface over the past 4.6 billion years in

sufficient quantity to form oceans.

ENERGY

Second, life needs energy. Without energy, virtually nothing would happen.

The most obvious source of energy is a planet or moon's host star, as is the case on Earth, where sunlight drives photosynthesis in plants.

The nutrients created by photosynthesis in turn are what the bulk of life on Earth directly or indirectly relies on for fuel. [50 Amazing Facts About Earth]

Still, countless organisms on Earth subsist on other sources of energy as well, such as the chemicals from deep water vents.

There may be no shortage of energy sources for life to live off.

TIME

Scientists have argued that habitable worlds need stars that can live at least several billion years, long enough for life to evolve, as was the case on Earth.

Some stars only live a few million years before dying. Still, "life might originate very fast, so age is not that important," astrobiologist Jim Kasting at Pennsylvania State University told OurAmazingPlanet.

For instance, the Earth is about 4.6 billion years old. The oldest known organism first appeared on Earth about 3.5 billion years ago, meaning that life might conceivably evolve in 1.1 billion years or less.

However, more complex forms of life did take longer to evolve —the first multicellular animals did not appear on Earth until about 600 million years ago. Because our sun is so long-lived, comparatively, higher orders of life, including humans, had time to evolve.

The first living things on Earth, single-celled micro-organisms or microbes lacking a cell nucleus or cell membrane known as prokaryotes, seem to have first appeared on

Earth almost four billion years ago, just a few hundred million years after the formation of the Earth itself.

By far the longest portion of the history of life on Earth, therefore, has involved the biochemical evolution of these single-celled micro-organisms, bacteria and archaea: we can find individual fossilized microbes in rocks 3.4 billion years old, yet we can only conclusively identify multi-celled fossils in rocks younger than 1billion years.

It is presumed that, over a few hundred million years of evolution, pre-biotic molecules evolved into self-replicating molecules by natural selection.

While some aspects of the subject are well understood, others remain clouded in mystery and are the source of much contention among scientists.

Although much progress has been made, there is still no single definitive theory.

Life, for all its complexity, is woven out of just 30 or so different molecules, constructed from some of the most abundant elements in the universe: oxygen, hydrogen, carbon, nitrogen, sulfur and phosphorus.

However, no one has yet succeeded in synthesizing a “proto cell” using basic components which would have the necessary properties of life.

The answer to the question Why Earth is suitable for living organisms? is not limited to the above explanation.

Hope the Post was Useful.

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