In environmental science, what would happen if carbon dioxide were completely removed from the earth's atmosphere?
Oh goody oh goody oh goody…Everyone Dies™Without CO2, every plant on Earth would perish in very short order. Photosynthesis would screech to a halt. The heterotrophs of the world, mostly bacteria and animals, would digest the plant material on land and in the sea, would consume all that dead plant material.That digestion would make CO2, but not nearly quickly enough to save any plants who might have survived the original die-off.But what this digestion would do is use up all of our oxygen, and that right quick. In mere days, the oxygen levels would be too low to support humans. Shortly thereafter, nearly every oxygen-consuming organism on Earth would be dead.This would leave just anaerobic life, and there is lots of it. Well, there was lots of it. Now it would absolutely overrun the planet. Without oxygen (which is toxic to anaerobes), these bacteria would occupy every niche on Earth, digesting organic material and multiplying at an alarming rate.The by-product of their metabolism is often methane (CH4) which is a potent greenhouse gas, many times more potent than CO2. The planet would warm quickly, roasting the anaerobes and boiling the oceans.Most anaerobes couldn’t survive on this hellish world, but some could - extremophiles. They’d be in their glory, living all over the Earth in large quantities.Our atmosphere, now loaded with CO2 and CH4, would be a home to all sorts of life - and that life might repeat a trick it pulled off once, billions of years ago. One day, many years after you’ve killed everyone, an extremophile might evolve photosynthesis. If it did, it would slowly consume the CO2 and make oxygen. That oxygen would first react with the methane, making more CO2. Eventually, though, almost all of the CO2 in our atmosphere would be replaced with oxygen.And then maybe, just maybe, oxygen-breathing life might evolve. Again.
How is it that some bacteria live in the hot springs of Yellowstone Park at temperature up as high as 73 C?
Extreme thermophiles have adapted unique ways to surviving harsh conditions. They're enzymes are specially designed to resist denaturing at high temperatures. What's really amazing is their DNA. Extremophile DNA is positively supercoiled (this describes the way it is twisted around itself) which makes it harder to separate the strands. DNA in most other species is negatively supercoiled (meaning it's wound up on itself in the opposite direction as positively supercoiled DNA). Since DNA is the building block of life, it makes sense that you need to be able to protect it from the environment. Extremophiles do just that by positively supercoiling it. It is much more resistant to heat denaturing than other DNA would be, which helps the bacteria to survive.
Why can't humans survive by increasing body temperature instead of gaining energy from food since both are energy?
The short answer is “Humans are not Malagasy fat-tailed dwarf lemurs”.You’re describing hibernation—kipping through the cold, or aestivation—decreasing your metabolism in the warm weather. A fair number of animals do one or the other. Some mammals hibernate; very few aestivate apart from (possibly)[1]this one:And even here, the lemur’s dry-season torpor is pretty much like hibernation. In common with many mammals, we can do neither.It would be great if we could. Bears seem to manage hibernation quite well—they don’t even drop their temperature much, despite their heart rate decreasing by 75%. If humans lie around for months without moving, they eat up their bones and muscles. Bears don’t. If we stopped peeing and pooing for that long, we’d die. Remarkably, bears produce almost no urea while hibernating, despite increasing their protein metabolism rather a lot![2] We still don’t understand this well. It’s pretty fine-tuned—if you starve a bear during summer, it won’t hibernate.And not all hibernators are the same either. Unlike bears, arctic ground squirrels can drop their body temperature to sub-zero temperatures (-2.7°C) while still not dying.[3] The hearts of humans become quite twitchy at about 30°C, and your ventricles are almost guaranteed to fibrillate at about 27°C—you die.We just aren’t built for what you describe.*My 2c, Jo.*I couldn’t help noticing how your question was altered a few times, even while I was answering it. It currently is “Why can't a human survive by decreasing their body temperature instead of gaining energy from food since both [are] energy?”Lemurs from Fat-tailed Dwarf Lemur; squirrel image from Finding which genes are activated or silenced by Arctic ground squirrels during hibernation.Footnotes[1] Physiology: Hibernation in a tropical primate[2] https://www.bearbiology.com/wp-c...[3] https://www.physiology.org/doi/f...
Is there any form of life on Earth that does NOT use water?
There is NO form of life on earth not requiring water for living.Life on this planet is dependent on fluid water, absolutely. There is no life on earth with steam or ice or without water. Although, there are forms of life that do not need any oxygen.There are specific organisms that can persist without water. Please distinguish “persisting” from “living”. Without water they do not live in that stage. These may be spores, rather dry states. They can persist in space, particles of dust pushed through our atmosphere and leaving it. Or sitting on a spacecraft on the moon. As well they may be encapsulated as inclusions in amber. They can be extracted and rehydrated from amber and be cultivated to bring them “back to live” from as far as 40 million years old samples (Diversity of Microorganisms Isolated from Amber; Revival and identification of bacterial spores in 25- to 40-million-year-old Dominican amber).But without water they need as well no oxygen, they DO NOT LIVE. In contrary, oxygen could destroy the chemical structures required to be “awakened” like Sleeping Beauty.Probably any and even human cells can be frozen and kept unknown many million years (the test is running for few decades only), IF the growth of ice crystals piercing the cells is avoided.Alien organisms may be constructed differently, but I cannot imagine how.