The Earth's environment is changing considerably and living conditions are difficult, causing organisms to continually evolve.
Competing with the environment, the earth's environment is changing and organisms living on earth will face more challenges and mutations. Generations of screening and evolution will leave behind increasingly complex biological structures.
The transition from aquatic to terrestrial life is a passive process. However, life born from water is separated from water and the environment becomes harsh. As a result, the potential develops, the diversity is richer. , and the environment becomes more difficult. Trial and error, therefore, in order to cope with more complex environments, more complex nervous systems emerged. It can be seen that the capabilities of the aquatic, amphibian, reptile, avian, lactating and nervous systems are progressive. And the most complex environment, the emergence of forests, followed by primates, up to man. As for land creatures, advanced intelligent creatures must have a developed brain, which accounts for a greater proportion of brain capacity. The brain is an organ that consumes a lot of oxygen, and the human brain consumes a quarter of it. This oxygen consumption cannot be met by the oxygen dissolved in water. Therefore, the most intelligent creatures in the ocean were also formed by land creatures entering the ocean, but these are after all accidental. Without a sufficient number of samples for evolution, it will be difficult to produce the next stage of evolution. Only organisms that take root on earth can develop a civilized society, develop an educated class and websites like Zhihu, and then ask the question "Why organisms havedo advanced people appear on earth? This can also be seen as a manifestation of the anthropic principle. That is, the emergence of this problem in itself proves that the problem must be established. If there is no land, perhaps a land consisting only of oceans (I don't know if we can still call it land) simply does not have sufficient primary productivity density to trigger a civilized society capable of asking questions.
Astrobiologists think it is unlikely that a type of life more complex than simple bacteria would be found on Mars.
Mars has always been considered the planet in the solar system most likely to host extraterrestrial life. Since the second half of the last century, NASA has landed numerous exploration devices on or in orbit around Mars, including Curiosity and Odyssey, and some of them are still operating today.
What these “see”detection devices, it is a desolate and lifeless land. The surface of Mars is essentially a desert without stable liquid water. The atmosphere, dominated by carbon dioxide, is thin and cold, and dust storms often occur. They dug up soil and analyzed it for traces of microorganisms and organic compounds. Nothing was found. The Earth-like Red Planet appeared to be a frozen desert bathed in deadly ultraviolet rays and seemingly devoid of any signs of life.
However, with the deepening of Mars exploration, scientists' views began to change. It might be too hasty to say that Mars is not a home for life. In recent years, more detailed photos of Mars have revealed what appear to be floodplains, dry lake bottoms and even remnants of ancient oceans.
The surface of Mars would be terrifying for any life that dependst liquid water as a source. Although there is some ice at the poles, But the temperature is too low to melt. Even if it melts, the liquid will evaporate quickly because Mars' atmosphere is less than 1% of Earth's atmosphere. Mars, which once had liquid water and heat, is estimated to have disappeared about 3.5 billion years ago. Today, the best hope for life there lies underground. Since some microorganisms can live deep underground, the energy for their survival does not come from sunlight, but uses chemical energy and thermal energy from gases and minerals in the earth's crust to convert it directly into biological energy, thus maintaining a food chain independent of surface organisms.