Question regarding Evolution. Please answer.

[human1111]

Hi all.
Recently I've got this simple, yet tough question regarding evolution.

If evolution happens only because of survival of the fittest, why did the life evolve beyond Bacteria/viruses and other singe cell organisms?

I mean viruses/bacteria can survive in the kind of environment no animal would.
Viruses and bacteria can reproduce much quicker, adapt and survive. Why isn't our planet simply a large depository of trillions of bacteria? Why did lesser (in terms of survival, reproduction) life form emerge?

Thank you.

[I, Brian]

I think the answer is supposed to be on the lines that gradual evolutionary processes led to bacteria that were more complex, and therefore able to achieve specific advantages within their environment. This process leads to general evolutionary arms race, that eventually led to complex forms. Does that help?

[alexa]

Originally Posted by human1111

If evolution happens only because of survival of the fittest, why did the life evolve beyond Bacteria/viruses and other singe cell organisms?

The evolution is a complex process. The key is hidden in your question. You know, evolution happens not only because the survival of the fittest (eugenics theory). Even the best put into an closed environement (an isle) let's say after a earthquake has no chances to evolve or survive without the contribution of his environment. Another factor is diversity of species.

Viruses are parasites without self mechanism of reproduction. They need other organismes to survive.

[human1111]

Originally Posted by alexa

.

Viruses are parasites without self mechanism of reproduction. They need other organismes to survive.

so what you are saying is that viruses (bacteria and other micro organisms)developed bigger organisms to feed on?

think the answer is supposed to be on the lines that gradual evolutionary processes led to bacteria that were more complex, and therefore able to achieve specific advantages within their environment. This process leads to general evolutionary arms race, that eventually led to complex forms. Does that help?

Unfortunately no. Why did gradual evolutionary process had to happen when micro organisms can survive where mutliple cell / big organisms could not.


thanks all for replies!

[Phyllis Sidhe_Uaine]

Originally posted by human1111
so what you are saying is that viruses (bacteria and other micro organisms)developed bigger organisms to feed on?

Not "feeding", but reproduction. Bacteria, parasites and viruses require certain conditions in order to replicate (and in the case of parasites, to feed, too.)

Another thing: viruses are biologically separate from bacteria (I don't know how to explain what I really mean, but viruses are not bacteria and vice versa.)

Phyllis Sidhe_Uaine

[path_of_one]

Viruses and bacteria are two separate classes of organisms. Viruses do not have the capacity to reproduce on their own; they must have a host to do so. In that, they are in the strange category of being sort-of alive, but not fulfilling all the requirements to be truly considered alive (which includes procreation). Bacteria, on the other hand, are single-celled organisms that meet all the requirements of being alive, and hence can procreate on their own through asexual reproduction (mitosis).

Why you are having difficulty understanding evolution is that your definition is incorrect. Evolution is not about survival of the fittest. It is change in genetic frequencies in a population over time. Evolution only can occur in a population, and only over time/generations. It is based on the following processes, working together:
1. Mutation- this is a random process that happens when DNA replicates before mitosis (cell division) or meiosis (the process that yields the sex cells of sperm and egg). Essentially, all life on earth is made of cells, and when these cells divide, they must make copies of their DNA for the new cell. When this occurs, the process sometimes randomly gets screwed up and mistakes are made in the copy. The new cell thus has a slightly different blueprint. Sometimes this change yields a change in the outward form (prototype) of the cell, and this change can be beneficial to the organism, neutral, or negative. If it is beneficial, it will cause a change that is advantageous to the organism's survival and reproductive capacity in its current environment. If neutral, it will make no effect at all. If negative, it will reduce the likelihood of survival and reproduction. In single-celled organisms, like bacteria, they only reproduce asexually but they do so at a very rapid rate, so the mutation rate is correspondingly high compared to more complex organisms. This is why we're constantly needing new flu vaccines and antibiotics- the random mutations of bacteria eventually produce strains that are resistant to the ones we have. In more complex organisms, like ourselves, we have the added process of sexual reproduction, which combines material from mom and dad, and so in those cases, only mutations in the sex cells matter for evolution, because only they will be passed on to the next generation.

2. Natural Selection- this is probably what you are referring to by "survival of the fittest."

Evolution really isn't about survival of the fittest. It's about who reproduces the most. This can be accomplished by living longer, as long as one's reproductive lifespan also increases, but it can also be accomplished by other advantages- like being able to protect one's mates better, or attract more mates, etc.

Natural selection is the process by which traits in the organism interact with the environment. Different environments can cause the same trait to be neutral, good, or bad for the organism. Traits that are bad for the organism will cause it to reproduce less, thereby passing on fewer of its traits to the next generation. In time, bad traits will either disappear completely from the gene pool (in extreme cases), or will become very rare. Traits that are good for the organism, on the other hand, will cause it to reproduce more, thereby passing the trait on in higher numbers to the next generation. In time, many or all individuals will show the trait.

A great example of how this works in humans is skin color. Around the equator (Africa, Central America, parts of India and Asia), the sun is very fierce. It is a good trait to have dark skin, because it blocks the ultraviolet light and keeps people from getting skin cancers, heat stroke, etc. So it is the most common trait, although albino and lighter skinned and eyed people occasionally crop up (there's an explanation for that, but it's long and detailed, so I'll leave it out). In the northern areas (even more so than the southern areas, due the tilt of the earth's axis), however, the dark skin trait is not good. It blocks the absorption of the sun's rays, and this is how we produce vitamin D, which is needed to avoid diseases like rickets. Now, along the equator, there is so much sunlight that it's OK that not much is absorbed, because it is plentiful enough to ensure that the bit that is absorbed is more than enough to produce adequate vitamin D. But in the far northern areas (think Scandinavia and the UK, for example), there is very little sunlight, and nearly none during half the year. Thus, over time, the population that migrated up there favors the trait more and more of light skin, which absorbs more of the sunlight. So you see, the same trait can be good or bad depending on the environment. If you're in Africa, and you are born with light skin, you'll have less kids because you'll be plagued with melanomas and heat stroke. If you're in Norway, and you are born with dark skin, you'll have less kids (and therefore pass on your genes less) because you'll be plagued with rickets.

3. Gene Flow- this is the process by which populations interbreed, thus making their genetics more similar to one another. Less species divergence is possible the more populations are interbreeding, because they are sharing mutations that arise over a broader population. Humans are fabulous at gene flow, which is why we're one of the most wide-spread species on earth, and yet still are all the same species.

4. Genetic Drift- this is the process by which populations become isolated, thus reducing interbreeding and causing their genetics to become more dissimilar. More species divergence is possible, because no one is sharing their genes. This is especially common due to geographic barriers, though that is not the only cause. Islands are a famous case. When organisms get stuck on islands and can't interbreed with those on the mainland, their population goes through a "bottleneck effect," in which only a few members are present that do not adequately represent the parent/mainland population. As these few members interbreed, their genetics become rapidly divergent from the parent population. You can often see this in only a few generations. This sets the stage, if sufficient time passes, for species divergence.

You see, evolution is a random process, as it is based on mutation, which occurs more or less randomly (there are a few cases, like radiation, that causes an increase in the rate of mutation). There is no "will toward complexity" or anything of the sort. Mutation just causes new traits to crop up occasionally, and these interact with the environment through natural selection, gene flow, and genetic drift, sometimes resulting in evolution and sometimes not. Over time, as the number of new traits increases in a population, it can eventually become so different from the original/parent population that interbreeding is no longer possible. At that point, a new species is born. The amount of different genetic material necessary for some major differences is not a lot- chimps and us humans share 98% of our genetic code. But that 2% makes a big difference.

Hope that helps explain it a bit.

[I, Brian]

Originally Posted by human1111

Why did gradual evolutionary process had to happen when micro organisms can survive where mutliple cell / big organisms could not.

Indeed, some bacteria can survive extreme environments where complex animals cannot particular thrive or develop to any degree. But then you have to consider the environments that are far less extreme and competition can become a lot more fierce.

[Jaiket]

path_of_one, good post, I enjoyed reading it. There are a couple of minor points I disagree with though.

Originally Posted by path_of_one

Sometimes this change yields a change in the outward form (prototype) of the cell...

For future reference, 'phenotype' is the word you should have used. Or at least from the context I believe that is what you meant. Easy mistake but could confuse people.

Originally Posted by path_of_one

Natural selection is the process by which traits in the organism interact with the environment. Different environments can cause the same trait to be neutral, good, or bad for the organism.

Just thought I'd add that this is a very important point, an adaptation beneficial in one environment can be detrimental in another. Not that relevant to the topic I suppose but imperative in understanding evolution for anyone who is unfamiliar with the subject.

Originally Posted by path_of_one

A great example of how this works in humans is skin color...

I've heard Darwin went to great length trying to argue the case against natural selection in regards to the differences (like skin colour) in races around the world. The vitamin D thing makes sense to me, but doesn't explain much of the evidence. This is off topic so I could PM anyone who is interested.

Originally Posted by path_of_one

You see, evolution is a random process, as it is based on mutation, which occurs more or less randomly (there are a few cases, like radiation, that causes an increase in the rate of mutation).

Evolution is the opposite of random, it is selective. It is without direction, perhaps that is what you meant?

Originally Posted by path_of_one

Hope that helps explain it a bit.

Taught me a couple of things! Cheers.

Originally Posted by human1111

If evolution happens only because of survival of the fittest, why did the life evolve beyond Bacteria/viruses and other singe cell organisms?...Why did lesser (in terms of survival, reproduction) life form emerge?

Why would you say lesser? Evolution isn't a race to perfection. Fitness is related to environment and multi-cellular organisms can better expliot that environment. Think of the advantages an animal has in the pursuit of survival and replication that a microbe doesn't.

[path_of_one]

Originally Posted by Jaiket

For future reference, 'phenotype' is the word you should have used. Or at least from the context I believe that is what you meant. Easy mistake but could confuse people.

You're absolutely right. Sorry about that- sometimes my mind wanders. Who knows where prototype came from? LOL- I can't wait til I get to use the "senior moment" excuse.

Just thought I'd add that this is a very important point, an adaptation beneficial in one environment can be detrimental in another. Not that relevant to the topic I suppose but imperative in understanding evolution for anyone who is unfamiliar with the subject.

Yes- I was trying to illustrate that with skin color in humans. Of course, there is the famous pepper moth case.

I've heard Darwin went to great length trying to argue the case against natural selection in regards to the differences (like skin colour) in races around the world. The vitamin D thing makes sense to me, but doesn't explain much of the evidence.

That skin color clines are based on natural selection is accepted among modern biological anthropologists. Skin color worldwide, when mapped, shows a tidy correlation with amount of sunlight combined with migration patterns of early human populations. There's more to it than just what I discussed, but the problems of dealing with too much/too little sunlight pretty much sum it up. The Americas show the same cline, but with less diversity, because the Americas were populated through migration leading to a bottleneck effect.

Evolution is the opposite of random, it is selective. It is without direction, perhaps that is what you meant?

Exactly. Sorry about the misnomer, but I was getting at evolution not being directional. I wanted to say evolution is not Lamarckian, but figured some folks might not know who Lamarck was. Essentially, evolution is a process that isn't based on the will of individuals to better their situation.

Thanks for picking up the loose ends!

[juantoo3]

Kindest Regards, all!

Thank you for the nice overview, path of one, good job! I wish I would have had something like this much sooner. I still have some troubles with evolutionary theory, but it is nice to have a simple and comprehensive overview.

Originally Posted by human1111

If evolution happens only because of survival of the fittest, why did the life evolve beyond Bacteria/viruses and other singe cell organisms?

I mean viruses/bacteria can survive in the kind of environment no animal would.
Viruses and bacteria can reproduce much quicker, adapt and survive. Why isn't our planet simply a large depository of trillions of bacteria? Why did lesser (in terms of survival, reproduction) life form emerge?

Welcome to CR, human1111!

The first thing I would have to ask is what makes you think the earth is not populated by trillions of bacteria? Between volcanic sea vents and the stuff that exists in oil deposits deep underground, the earth is populated by even more than trillions of bacteria. Stephen J. Gould wrote to this issue, although it escapes me exactly where at this moment. "Rocks of Ages" perhaps, but it might have been in a magazine article...anyway...

According to Gould, bacteria will continue to survive long after even the cockroaches have disappeared. Path of one touched on some important matters concerning this, but Gould was of the opinion that single-celled creatures were the source and well-spring from which all other life emerged, not just once but several times. Looking back in the geological history, there have been several mass exterminations, all open to conjecture as to why. But always, without exception, bacteria continued to survive. If there is anything to evolutionary theory beyond a method of understanding, then bacteria are the source from which all life emerges.

Originally Posted by path of one

But in the far northern areas (think Scandinavia and the UK, for example), there is very little sunlight, and nearly none during half the year.

I realize this is the simplistic explanation, but something about it has always made me wonder...

Yes, at the extremes of the poles there is little sunlight during half of the year, but during the other half it is even more intense than at the equator! 24 hour daylight. (I might even add there is a thinner atmosphere, less to deflect harmful rays) At the equator, there is half day and half night, roughly speaking, for the whole year, which averages to about the same amount of daylight all over the globe. So the simplistic explanation has its faults.

Of course, one could argue about having to bundle up against the cold. During the Ice Ages, there is probably some substance to this line of thought. But what of the times in history when the poles were not locked in ice? There are remains of tropical plants to be found in the arctic...

[path_of_one]

Originally Posted by juantoo3

Yes, at the extremes of the poles there is little sunlight during half of the year, but during the other half it is even more intense than at the equator! 24 hour daylight. (I might even add there is a thinner atmosphere, less to deflect harmful rays) At the equator, there is half day and half night, roughly speaking, for the whole year, which averages to about the same amount of daylight all over the globe. So the simplistic explanation has its faults.

I believe part of it is the tilt of the earth's axis, making the sunlight less direct, and the other part of it is how much time there is cloud cover. But, yes, I am giving a very simplistic explanation for a very complex phenomenon that is not fully understood in science.

[juantoo3]

Dug this up from the vault, a lot of people put a lot of effort into some 13 pages of responses. Maybe it will help:
http://www.comparative-religion.com/...7&page=1&pp=15

[juantoo3]

Kindest Regards, path of one!
Thank you for your response!

Originally Posted by path_of_one

I believe part of it is the tilt of the earth's axis, making the sunlight less direct, and the other part of it is how much time there is cloud cover. But, yes, I am giving a very simplistic explanation for a very complex phenomenon that is not fully understood in science.

[Faithfulservant]

I posted it on the other evolution thread there is a difference between microevolution and macroevolution.. humans with skin color change is microevolution... If its ok with the moderators I would like to post a link explaining the difference for those who may not know what they are.

http://anthro.palomar.edu/synthetic/synth_9.htm

[path_of_one]

Great link, and I agree. Microevolution and macroevolution work the same way, just on different scales. But they are based on the same mechanisms. So new species arise due to mutations worked on by natural selection, gene flow, and genetic drift, and yes, I agree that it is generally in a punctuated equilibrium format.