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Are there bacteria living today which can synthesize the full range of materials necessary for life from simple molecules that would have existed on early Earth, or have they all died out?
Oh yeah, Nicole, what microbiologists call "the source bacteria" which originated in that warm primordial soup we evolved from are still found today in similar conditions. But none of them will ever, ever manage to evolve like we did. Too many things had to go just right beginning two billion years ago: environmental and climactic conditions; RNA replication; the perfect food sources; and non-lethal predation from other viruses and bacteria, and then from fish, reptiles, and competing animals.
Plus, we had to make the crucial jump from prokaryotes to a type of multi-cell bacteria called eukaryotes, which also gave rise to other animals, plants, fungi and protozoans. The differences between eukaryotes and other organisms, known as prokaryotes, are numerous and crucial.
And again, as we always have to remember: time, time, time. It's doubtful there is enough left of it on this planet which could serve as a perfect breeding ground--petri dish?--to foster another evolution which culminated in humans. All it would have taken is one of the thousand of earlier factors to change by a small degree to result in us not being here. If the history of man, beginning with our climb out of the warm pond were condensed to a 24-hour day, beginning at midnight, then humans arrive on the scene just a few seconds before the following midnight.
Here's one that I have always thought about when reading about evolution or in the "human evolution" section in museums.
Humans, i.e. Homo Sapiens had close ancestors that were very human-like. Why did they die out and why did the Homo Sapiens survive? What genetic advantages did humans possess over the others?
Again, remember that it was a very gradual process, and the word "absorbed" in regards to the Neanderthals might be more accurate than to say they "died-out." As far as genetic advantages, again, our larger and more complex brai with superior planning and tactical capabilities was the big genetic advantage. AND, as in the casein another post where I talked about our bacterial beginning, remember that many things had to go just right for us to prevail. It wasn't as if we had a huge, commanding dominance. Some luck was involved!
Lastly: I have to include one theory as to why we won-out, but it's hotly debated:
And that is that homo sapiens indeed did use violence to prevail.
The theory that early humans violently replaced Neanderthals was first proposed by French palaeontologist Marcellin Boule (the first person to publish an analysis of a Neanderthal) in 1912.
Another supporter of competitive replacement is Jared Diamond who points out in his book "The Third Chimpanzee" that the genocidal replacement of Neanderthals by modern humans is similar to modern human patterns of behavior that occur whenever people with advanced technology invade the territory of less advanced people. The advanced technology in ths case would have been our weapon-making edge enabled by our superior brains.
I just wanted to offer to answer any questions or even discuss any comments or observations you might have about the fascinating field of Biology. I have had a lifelong love affair with it, beginning from when I got my first microscope at 10 years-old. I took my Master's degree in Biology from the University of California at Santa Cruz and am currently working on my Ph.D. My field of specialty is in Evolutionary Biology, and also in Human Physiology and Sports & Exercise Science. I currently work as a physical therapist.
Fire away and let's have some fun, talking about the science that without it, none of us would be here!
I have a biological question. Or more accurately, an astrobiological question.
What is the lowest atmospheric pressure any air-breathing animal (amphibian, reptile, bird, or mammal) can endure, and still be able to live a long and productive life (eat, sleep, reproduce, etc.)?
The purpose of the question is an attempt to determine the minimum atmospheric pressure an exoplanet can have, and still be able to support air-breathing life forms. We already know that the lowest atmospheric pressure an exoplanet must have in order to support liquid water: A minimum of 7 millibars at 0.01°C. Obviously air-breathing life forms require more atmospheric pressure, but how much more?
Talking of Neanderthal genes, we are all supposed to have Neanderthal genes in us but apparently West Africans have the lowest percentage. This they say is because West Africans are descendants of the originators of Neanderthals as all other modern humans are but Europeans have reintroduced Neanderthal genes. OK, so my 'knowledge' is a bit sketchy here so if you could fill in the blanks and correct the errors, it would be greatly appreciated.
Then I have another question, that being, what is life? A dried and lifeless seed will spring into life when given some water. Some living organisms can dry out completely then spring back into life, again when given some water.
Hey 303!
Actually it's a tad innacurrate to say that "a dry and lifeless seed will spring into life when given some water" Oh, that seed might look dry and lifeless to you when looking at it from the outside, but if you supply sufficient hydration and it DOES germinate, i.e. spring into life, then you can rest-assured it was not lifeless inside, but rather, it contained that all-important DNA molecule. Nature's blueprint for life.
In animals the DNA lies within the mitochondria of the cells, which are basically like little "power plants." In flora, though, the deoxy-ribo nucleic acidic molecule is found in the "chloroplast."
All fully developed seeds contain an embryo and, in most plant species some store of food reserves, wrapped in a seed coat. (Some plants produce varying numbers of seeds that lack embryos; these are called empty seeds, and they never germinate.) But most seeds go through a period of dormancy where there is no active growth--this might be what you meant when you referred to it as being lifeless! And, during this time the seed can be moved to a new location and/or survive adverse climate conditions until circumstances are ripe for growth. Dormant seeds are ripe seeds that do not germinate because they are subject to external environmental conditions that prevent cell growth.
Last edited by Ruffin_Ready; 10-11-2014 at 12:04 PM..
I have a biological question. Or more accurately, an astrobiological question.
What is the lowest atmospheric pressure any air-breathing animal (amphibian, reptile, bird, or mammal) can endure, and still be able to live a long and productive life (eat, sleep, reproduce, etc.)?
The purpose of the question is an attempt to determine the minimum atmospheric pressure an exoplanet can have, and still be able to support air-breathing life forms. We already know that the lowest atmospheric pressure an exoplanet must have in order to support liquid water: A minimum of 7 millibars at 0.01°C. Obviously air-breathing life forms require more atmospheric pressure, but how much more?
Thanks.
Hey Glitch!!
You're gettin' a little outside of my comfort zone of knowledge here (LOL), but to begin I can tell you that insofar as minimum atmos. pressure for humans to endure without lapsing into hypoxia,, the effects of high altitude on humans are considerable. The percentage saturation of haemoglobin with oxygen determines the content of oxygen in our blood. After the human body reaches around 2,100 m (7,000 feet) above sea level, the saturation of oxyhaemoglobin begins to plummet ] BUT! the human body has both short-term and long-term adaptations to altitude that allow it to partially compensate for the lack of oxygen. For example, being a runner I know that Athletes use these adaptations to help their performance. There is a limit to the level of adaptation; mountaineers refer to the altitudes above 8,000 metres (26,000 ft) as the "death zone", where no human body can acclimatize.
As for the minimum requirement for our friends in the flora kingdom, you might want to check-out this link, from a site I used quite often in my undergrad studies:
Sorry...forgot about the "neanderthal gene" question! But yeah, the genetics guys say they can still trace about 1/5th of our genome to begin shared withour common ancestor Neanderthalis Man. What I think is pretty interesting is that the vast majority of those genes (about 80%) are the one responsible for producing keratin fibers, which you remember is crucial in having healthy & strong skin, fingernails, toenails, and also hair. (this makes sense, huh? Especially when you look at a rendition pic or drawing of a Neanderthal!) It is thought their skin was about twice as "tough" as ours; their hair much courser and faster growing, and that their nails grew faster & stronger as well.
When you were working on your Masters, did you feel like you were a slave? Did you have to a lot of extra stuff, not necessarily for the degree, but part of going through the hoops of that profession? Had to do it because you were there and if you wanted to graduate, you better toe the line and do what they "asked" you to do?
When you were working on your Masters, did you feel like you were a slave? Did you have to a lot of extra stuff, not necessarily for the degree, but part of going through the hoops of that profession? Had to do it because you were there and if you wanted to graduate, you better toe the line and do what they "asked" you to do?
LOL--the term "slave" might be a bit harsh, but when I was first applying for the M.S. Program I did feel like the University sure made us jump through a lot of hoops, almost as if they were making sure we were motivated enough so we wouldn't dare to waste their precious time. I had to: get a good grade on the GRE test; get the recommendations of two faculty members/former professors; write a convincing letter of intent and plan of action as to WHY I wanted to enter the Master's Program, and then also get my Thesis subject approved. (which was: "Evolotionary Psychological Traits in Modern Humans").
But after all that it was not so bad. The key in a post-grad program is, I think, to hook-up with a good mentor or academic advisor on the faculty who can guide you through the process, and who knows what they look for. Finding a good work/study program is valuable as well. My University is actually "friendlier" than a lot of them are to post-grad students; we h ave a pretty liberal mindset here in Santa Cruz.
I'm working on my doctoral dissertation now, and once you get to this point they pretty much leave you alone. It's all about "publish or perish." LOL....
I see you're from the Texas hill country! I've spent a good amount of time in Austin and still have family there. A nephew at UT. where are you? Kerrville or Dripping Springs maybe? My favorite part of Texas!
You're gettin' a little outside of my comfort zone of knowledge here (LOL), but to begin I can tell you that insofar as minimum atmos. pressure for humans to endure without lapsing into hypoxia,, the effects of high altitude on humans are considerable. The percentage saturation of haemoglobin with oxygen determines the content of oxygen in our blood. After the human body reaches around 2,100 m (7,000 feet) above sea level, the saturation of oxyhaemoglobin begins to plummet ] BUT! the human body has both short-term and long-term adaptations to altitude that allow it to partially compensate for the lack of oxygen. For example, being a runner I know that Athletes use these adaptations to help their performance. There is a limit to the level of adaptation; mountaineers refer to the altitudes above 8,000 metres (26,000 ft) as the "death zone", where no human body can acclimatize.
As for the minimum requirement for our friends in the flora kingdom, you might want to check-out this link, from a site I used quite often in my undergrad studies:
I realize that I was putting you on the spot, because it is not just about atmospheric pressure, but also the percentage of oxygen that is in the atmosphere.
At 2,100 meters the atmospheric pressure is 78.9 kPa. At 8,000 meters the atmospheric pressure is 35.6 kPa. In both cases the atmospheric oxygen content is 21%.
According to the link you provided, before NASA put up Skylab in 1973 the environment they subjected the astronauts to had an atmospheric pressure of 34 kPa, with an oxygen content of 70%.
Which seems to imply that the higher the oxygen content of the atmosphere, the lower the atmospheric pressure can be - to a point. However, I do not think the environment NASA created for the astronauts prior to 1973 was intended for long term exposure (meaning decades in this case). Besides, an exoplanet with a 70% oxygen content is extremely unlikely. The lowest the oxygen content has been on Earth since the Cambrian was ~15%. The highest the oxygen content has been on Earth since the Cambrian was during the Carboniferous at ~35%. It has only been in the last ~40 million years where the oxygen content of the atmosphere has leveled out at 21%.
So as far as Earth is concerned, with an atmospheric content of 21% oxygen, as long as the atmospheric pressure is above ~80 kPa, humans (and presumably most other fauna) can live long lives. If the oxygen content of the atmosphere is higher than 21%, then the atmospheric pressure can be lowered. At 30% oxygen content in the atmosphere, humans could probably handle as little as ~70 kPa and still live long productive lives. At 15% oxygen content in the atmosphere, humans would probably need to be at least ~85 kPa to live long productive lives. Whereas, an atmospheric pressure of less than ~50 kPa (~5,400 meters [~17,700 feet]) with a 21% oxygen content in the atmosphere would probably not be a healthy environment for long term survival.
I appreciate your answer, and the link. It gives me an approximation of the minimum atmospheric pressure required for the long-term survival of air-breathing life forms.
Oh yeah, Nicole, what microbiologists call "the source bacteria" which originated in that warm primordial soup we evolved from are still found today in similar conditions. But none of them will ever, ever manage to evolve like we did. Too many things had to go just right beginning two billion years ago: environmental and climactic conditions; RNA replication; the perfect food sources; and non-lethal predation from other viruses and bacteria, and then from fish, reptiles, and competing animals.
Plus, we had to make the crucial jump from prokaryotes to a type of multi-cell bacteria called eukaryotes, which also gave rise to other animals, plants, fungi and protozoans. The differences between eukaryotes and other organisms, known as prokaryotes, are numerous and crucial.
And again, as we always have to remember: time, time, time. It's doubtful there is enough left of it on this planet which could serve as a perfect breeding ground--petri dish?--to foster another evolution which culminated in humans. All it would have taken is one of the thousand of earlier factors to change by a small degree to result in us not being here. If the history of man, beginning with our climb out of the warm pond were condensed to a 24-hour day, beginning at midnight, then humans arrive on the scene just a few seconds before the following midnight.
Well, I had watched some video on Youtube a while back about sulfur-reducing bacteria and some basic biochemical synthesis cycles, but I didn't quite follow it all. What are the chemical cycles to get from inorganic molecules to chemicals making up a cell, that are in place today?
I know that it's not hard to get to protein once you have amino acids, and to get DNA from its bases, but do bacteria living today really synthesize those things from scratch, like nucleic acids, and if so, what is the chemical pathway, and what carbon-containing molecule is the source? HCN? CH4? What is the sulfur source? H2S?
If you had a vat of just HCN, CH4, HCHO, H2S, etc. with no DNA or protein, and put the right bacteria in it, could they consume the available energy and multiply successfully?
What about if you started with the chemicals in the Miller-Urey experiment and their products? Any amino acids produced inorganically would presumably have equal mixtures of left-and right-handed molecules. Can presently living bacteria make use of the right chirality without the wrong handedness molecules getting in the cycle and messing it up?
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