Long Answer Questions (Answer in about 60-70 words) :
1. What major factors have enabled life to evolve and survive on the planet Earth.
Answers
Answer:
Explanation:
The factors that have enabled life to evolve on earth are the same as the factors that allow life to continue to exist on earth at the present. Those are, in no particular order:
Distance from the sun
Earth is in the sweet spot, not too far away, not too close. Liquid water is the dominant form of water on the planet surface and it has particularly good, or really, absolutely critical characteristics for all present forms of earth-based life.
Mercury and Venus are too close, heated to boiling, preventing any complex chemistry.
A large moon (as another answer mentioned) providing not only tidal motion to the seas, which would promote the growth of inter-tidal life, leading to land-based life, but also tidal stretching forces heating the interior of the earth, contributing to volcanism and adding to heat created by radioactive decay.
It’s not known if this is critical, but it’s hard to imagine life as we know it developing without it, due to the tides. In addition, without the moon the planet core would cool faster, perhaps fast enough to truncate evolution by degrading the magnetic field, etc.
A strong magnetic field which comes from the presumed spinning core of iron at the center of the earth.
Without this field, the atmosphere would be stripped off the planet by the solar wind and complex chemicals broken down by ionizing radiation.
The presence of large planets in the outer solar system, particularly Jupiter and to a lesser degree Saturn.
These huge gravity centers sweep space of most incoming rocks and such and even capture them in the asteroid belt, preventing earth-shattering impacts on too frequent a scale.
The specific temperature of the sun.
It’s not known if life could form around cooler stars such as a red giant or brown dwarf, but hotter stars produce progressively more ionizing radiation which acts counter to complexification by stripping atoms of electrons and causing chemical degradation.
The distance from the galactic center.
Closer in to the galactic center, the environment of space is progressively more hazardous, with higher levels of gravitational interaction disturbing system equilibria, higher levels of ionizing radiation, and a greater number of potential impactors being flung about by relatively unstable gravitational environs.
The size and composition of the Earth.
The gas giants may have a solid core at the center, but it’s pretty unlikely that conditions are suitable for complex molecular structures to form. Jupiter emits a huge amount of ionizing radiation itself, and is sometimes referred to as a “failed star”, close to, but falling short of enough hydrogen to initiate fusion. In addition to the radiation, the incredible gravitational pressures create liquid-state gases that are not conducive to the chemistry that comprises life as we know it, neither in type nor complexity.
The smaller planets don’t have enough gravity to maintain either an atmosphere, nor volcanism, nor a magnetosphere-inducing spinning core of iron. Size matters. Venus is close to earth size, but too close to the sun. Mars is too small to maintain volcanism or an atmosphere.
Adequate water.
We know of no alternative to water. It acts as a literal and metaphoric lubricant for life, allowing transport of resources, breakdown of previously formed and sequestered mineral resources, transport of chemicals within and without cell walls, etc.
Mars has water, perhaps lots of it, but it is in either a hard frozen state or is sublimating into vapor, only to be stripped off by the solar wind or falling again as ice at the poles. No liquid or not much by Earth standards.
There are no doubt many more and more finely divided and specific factors that one could name, given differing points of view and hypotheses of what specifically is important for the development of particular characteristics. It’s certain that if Earth were restarted the resulting forms of life would not be the same. There are far, far too many specific, random events that have happened, from the infinitesimal to the cataclysmic, for the history of the development of life to have any chance at all of arriving at a convergent point with our own. It is likely, however, that analogous forms of life would form because the evolutionary niches would always be there - there would be land, so land-based life would form; the opportunity for locomotion would still exist, therefore giving rise to forms that optimize swimming, crawling, flying, etc.; there would be a base level upon which other levels could depend as resources for already gathered and stored energy; and so on. So, not the same, but evolving nonetheless.