A biology question

[Princess Rose]

Sure, the likelyhood that other intelligent life would be bipedal is extremely low (without some sort of lantern-hung explanation such as is given in both Star Trek and Mass Effect (that a mysterious race of Aliens did it)),

Actually, if I remember correctly, in Mass Effect they never said that humans or any other species other than the Keepers or the Collectors were specifically altered in any defining way. Certain missions, like the mission with those monkey-like creatures in ME1 indicate that the Protheans observed humans from Mars. Other events, like conversations with Sovereign or some catches on the Collector ship/base we learn that Reapers have been using technology to narrow the direction in which the species innovate, but it was never suggested that they were doing anything to bipedal's specifically.

They do however say that bipedal life is the most conducive for sapient life in Mass Effect, but they never actually explain why.

Actually, it is specifically stated that the Protheans altered the DNA of the next generation of races - hence why there were Prothean ruins near each of the major races. Humans, Turians, Asari, and Salarians, at the very least, were genetically manipulated by the Protheans.

They don't say HOW they manipulated our DNA, but it isn't that far of a stretch. The Protheans were bipedal - hence everyone else being bipedal.

 

[JesterRaiin]

Couldn't life come to existence and evolve in, let's say, a lake of sulfured acid....or even better a lake made out of some other element that we haven't discovered yet?

Our current knowledge "forbids" such possiblity, however our knowledge is far from being complete.

Also couldn't some life forms evolve in such a way that they breathe nitrogen or CO2 instead of oxygen? Can life come to existence in a completely different environment?

There are microrganisms on Earth that doesn't breathe at all, live in very harsh environemnt (great depths, under ice, deep within Earth's crust). I'm not sure where, but i've read some article about lifeforms discovered in Mariana Trench that is supposed to evolve from a little different patterns that pretty much everything else we encountered. Scientists claim that there are bacteria on some meteors and even on the surface of Mars, however some people claim that it's more possible that samples were stained by our own equipment...

Point is : opposite to some claims, we do not know all life forms that live here, beside us. It would be stupid to simply rule out any possibility simply because for now there's no proof for its existence.

 

[Johann610]

If you peel it all away to the core of what constitutes "life", we are looking for energy-exchange reactions, and that means fluids. And while gases can fit the bill on occasion, the more likely arrangement is in liquids, which have less tendency to fly apart.
And from a fly-over-and-scan perspective of deep-space probes, water is the easiest liquid to identify.

 

[Terracrete]

My point remains and you in fact reinforce this, all forms of life are not just limited to OUR definition of life. Even as you spoke you references process that are limited to earth based lifeforms and process which are common -on this planet-.

This is stepping into a definition consideration rather then a science one.
Humans have a strong tendency to establish arbitrary classifications to the universe, it is through these classifications or definitions that we are able to rationalize and apply the above mention techniques of prediction and extrapolation.

I listed above the currently accepted definition of life as...

An entity which demonstrates all or most of these properties: Homeostasis, Organization, Metabolism, Growth, Adaptation, Response to stimuli, and Reproduction.

Sure we could re-define this to state...
An entity which demonstrates all or most of these properties: Organization, Growth, Adaptation, Response to stimuli, and Reproduction.

If we were to remove Metabolism and Homeostasis as requirements we can expand the parameters of what is accepted as life. However in doing so we allow (as an example) inorganic crystal formations to be categorized as living, which one no currently does. We could further alter the definition to the point where anything can be included or excluded from the definition of life.

In addition we currently allow multiple exceptions to requiring all of these attributes (which the definition covers); mules as an example are unable to reproduce (side note mules are not considered to be a unique species because of this fact), but we arbitrarily define mules as living.

There are entire genres of science fiction that seek to explore the understanding of the term life when applied to new pseudo-organisms or even AI.

The point I'm making is that the nature of the universe does not care what we call something, each entity is what it is.

So when saying: That while currently all life as we know it utilizes carbon and all life as we know it originated in water, but that these are not necessarily requirements if we change the definition of life is tantamount to saying that 2+2=12 is true if we change our definition of number numerals from base 10 to base 3.

Utilizing the established definition of life it is extremely unlikely, if not then impossible, that life exist without water, or equally unlikely, without O2.

 

[Terracrete]

Interesting side fact, sentience and self-awareness are not requirements for life. Bacteria for example has no concept of self-awareness and is most definitely not sentient.
This makes these two qualities independent of the life definition.
So just because you meet a talking cloud specimen on a new undiscovered world does not mean it is alive.
For you sci-fi enthusiast, this also means that poor Data is not considered alive by the currently accepted definition of life. But he could easily be argued to be sentient and self-aware independently of this fact.

 

[Terracrete]

Ok, to have life develop, a transition needs to be made from chemical to biological systems, the only known method for doing this that we know of is abiogenesis (a youtube channel potholer54 explains it really well http://www.youtube.com/watch?v=v8nYTJf62sE)
This needs simple carbon molecules in a neutral solvent, which varies in temperature between 30-80 degrees centrigrade, water is both incredibly common and perfectly neutral, so is perfect, other solvents dont tend to exist in large enough quantities for abiogenesis likely to occur, and may break down over time.

This is 100% correct

The most credably accepted "spark of life" is that established by the Miller-Urey experiment
http://en.wikipedia.org/wiki/Miller-Urey_experiment

This experiment shows how amino acids are formed (organic material) from inorganic material utilizing the exact conditions that our planet was under at the time.

 

[Stoic raptor]

Okay I was strolling along minding my own business after watching some Zero Punctuation when I came across your question.

Water due to interactions between the 2 hydrogen protons of one water molecule being strongly attracted to the electrons of oxygen atoms of adjacent water molecules, hereby refereed to as hydrogen bonding gives water some very unusual properties that are critical to aiding in the development of life.

1. Water in solid form (ice) is less dense then the liquid form (water), this is the reverse the normal. Because of this ice floats in water (normally a solid material would sink when placed in to its liquid form.

1a. Because of the above property it is very difficult to freeze entire bulk body of water. As water deep below the surface is cooled, due to lack of exposure from the sun, it rises to the surface and heats up again where by it once again lowers back to the depths. This process is called convection.

2. Water is a universal solvent. Water can dissolve almost anything. This is critical for developing cellular structure, cellular structure requires interactions between charge particles such as potassium, chlorine, and sodium which water can enable by dissolving these charged salts into solution.

3. Water has strong capillarity properties. Capillary ability of a liquid to flow against gravity where liquid spontaneously rises in a narrow space such as a thin tube, or in porous materials such as paper or in some non-porous materials such as liquified carbon fiber. This allows water to reach the top of trees from the roots.

4. Based on the size of a water molecule it should be a gas at standard temperature and pressure, but due to hydrogen bonding it is a liquid. This is important because water's small size as a liquid allows it some special properties, such as osmosis.

There are many other unique properties of water which I wont' cover due to space limits and my not wanting to

Here I was all excited because this is something I know well, and I was going to make a big post explaining why water is so important.

Then I got ninja'd

So I will try to add what little I can

Ice is less dense than water. If this wasn't true, lakes would freeze from the bottom up. That's how a lot of aquatic animals survive the winter.

Water also has a high heat capacity. That means it takes a lot of energy to change it's temperature. This is very important for maintaining your body temperature, something that cannot change too much.

Water is also polar. Meaning that the atoms have a slight charge on them. To be specific, the oxygen is negative and the hydrogen is positive. This is how capillary action works, and how water is able to dissolve so many things. The water molecules easily attach to a surface, like glass, and the rest follow. The water molecules also surround ions like salt, breaking the bonds and essentially dissolving them. The polarity also helps maintain structure. I am not going to explain it in detail, but basically non-polar molecules (fats and oils) and polar molecules work together to keep the cell membrane (and other things) stay together.

Another little tidbit about water is that its transparent. Meaning light goes right through it. Very important for plants who need light for photosynthesis, they can't have the water in them blocking the light.

 

[Terracrete]

Here I was all excited because this is something I know well, and I was going to make a big post explaining why water is so important.

Then I got ninja'd

Ninja'd!

 

[Terracrete]

We'd want to find species we can live with/eventually possibly breed with.

Ewww...

 

[Dutch 924]

I think most people believe life depends on H2O because without it, nothing would've survived on Earth. It's understandable that people assume it must work on other planets. It also wouldn't be possible for life forms to evolve out of acids or alkalis because they would be killed instantly due to the pH levels.

We do know that it's possible for lifeforms to breathe something other than oxygen, because we have lifeforms like that on Earth: plants and trees. I don't see why it wouldn't work on other planets.

 

[dark-mortality]

As an astronomy enthusiast (with very little actual scientific knowledge) and a complete lack of knowledge of biology there is one thing that always puzzled me whenever i would watch one of those shows about space, and more specifically about searching for extra-terrestrial life.

Why do we always assume that for the life to exist, the conditions on the planet have to be at least somewhat similar to those of earth?
More specifically the presence of liquid water.

Now i can understand why it's safe to assume that there is no life on super cold or super hot planets, due to the fragility of the organic matter, but why is H2O considered a magical ingredient for life.

Couldn't life come to existence and evolve in, let's say, a lake of sulfured acid....or even better a lake made out of some other element that we haven't discovered yet?

Also couldn't some life forms evolve in such a way that they breathe nitrogen or CO2 instead of oxygen?
Can life come to existence in a completely different environment?


I remind you that my knowledge of biology is very very limited, so i would like someone with a bit more insight to explain those things to me

You have to remember one thing: Scientists are narrow-minded, and extemely rarely thinks about solutions outside the norm. The reason we have discovered anything at all is because it was the open-minded scientists believed something else than what everyone else did.

But then again, it would have been awesome to meet a slime-monster made of acid that lived of human sweat. (No matter how strange that sounded.)

 

[Level 7 Dragon]

Well, most or less likely life can be anywhere and heck, why does it have to be made out of matter?! Life can be made out anything and why life, other, more odd forms of existence.

Yet to answer those questions we have to first find out where the hell did life actually came from :|

 

[Wrists]

We're in Biology now in my grade 10 science class, and we recently covered carbon/nutrient cycles. For us to live we need Oxygen, but if we were to breath it all up then we'd die so plants us photosynthesis, taking in sunlight and CO2 to create its own nutrients, in the process emit Oxygen...sorry for the long story, short; Plants don't 'need' oxygen

You're missing out a very important part of the processes by which life continues. One of which is respiration, the process by which glucose molecules react with oxygen to trap energy within ATP molecules. Plants do this as well as animals. So do protoctista and prokaryotes. Therefore they all need oxygen.

In response to the actual thread...well I'm thinking it goes back to the idea that "The universe is the way it is, because if it weren't we wouldn't be here to see it." Life is based on carbon and water (along with the other essential molecules like nitrogen and phosphorous)because that's the easiest way for it to happen.

Way to answer the thread without saying anything helpful, eh?

 

[Dags90]

We do know that it's possible for lifeforms to breathe something other than oxygen, because we have lifeforms like that on Earth: plants and trees. I don't see why it wouldn't work on other planets.

To be pedantic, and I do love me some pedantry, plants "breathe" oxygen. That is to say, they use oxygen to convert glucose into ATP during aerobic respiration. The use of CO2 during photosynthesis is not comparable to respiration.

 

[dmase]

Very recently they've found living prokaryotes in the bottom of a lake with heavy concentrations of... I wanna say Arsenic. There should be nothing there and yet there is.

From what I know about biology the theory that these conditions are the only ones that allow for organism growth and development is mostly outdated. A lot of biologists do believe there are other conditions that organisms can grow... maybe not thrive but it still counts.