Jump to content

Original Think Cells?


Recommended Posts

If you follow the history of evolution all animals and plants once originated as single celled organisms and have evolved to adapt to their surroundings. But how did these original cells have the genetics or brains to come up with these adaptations?

For instance, fair enough that original single cells evolved feelers to grab onto their surroundings, this could have been acheived through mutation. But how does an organism learn that it can view the world on a whole new level through sight and create powerful eyes? At what stage were any parts of a single cell, such as the normal parts of a cell able to presume that light could be seen and what parts started utilising it?

It just seems to unlikely that this could happen, even over thousands of millions of years. And even if it could, surely plants would have utilised sight too.

What posssible advantage would an original cell, or even a even multi-celled organism gain from viewing surroundings, and how did the cell think to create a way to veiw them.

This kind of problem can be seen in most of the other extreme senses as well. It would be great to know if there was a theory out there.

 

Cheers

 

Nick:-)

Link to comment
Share on other sites

It learns that it can view the world through sight when the mutation happens that lets it see. Sight isn't necessarily an advantage though. A plant wouldn't have much use for sight, since it couldn't move to avoid or go to anything it saw anyway, so it wouldn't have evolved sight. And adaptations don't happen because the cell thinks of them (except for some behavioral), they happen because of unconscious mutations.

Link to comment
Share on other sites

By the time an organism developed sight, it would've been multi-cellular... perhaps some bundle of nerve endings (that served some other purpose originally) mutated in such a way that made the sensitive to sight... This adaption became naturally selected as helpful to the survival and reproduction of the gene, and with further mutations you end up with an eye that can not only sense light, but also have a brain that can interpret what the messages mean to a more meaningful extent.

 

All "big" evolvutionary leaps started out as something far less helpful (but enough to be selected for).

 

And to your plant question... its obvious that at no point in plants evolutionary timeline that site held any advantages... think about it, plants are rooted to the ground, they do not move... sight would be a hinderance, something extra that would need more energy to grow in such an organism.

 

That's why you don't get ogled by trees when you walk through a forest ;)

 

EDIT: wow aren't I helpful? I posted a long-winded version of the guy before me without realizing it -.-' took too long to post I guess haha

Link to comment
Share on other sites

It learns that it can view the world through sight when the mutation happens that lets it see. Sight isn't necessarily an advantage though. A plant wouldn't have much use for sight, since it couldn't move to avoid or go to anything it saw anyway, so it wouldn't have evolved sight. And adaptations don't happen because the cell thinks of them (except for some behavioral), they happen because of unconscious mutations.

 

 

You have a good point save to state that evolution has a state of mind. You are better off in all reality viewing the organism that happens to be present in the ecology really. That’s where most people fail really in trying to think about life. They ignore ecology overall.

Link to comment
Share on other sites

Ok eventually evolution does cover all. But how does an organism decide to keep sight on the basis that the first mutation must have been pretty poor? The visibility wouldn't have been helpful at all, if even achievable. Plus it would have used as much energy or more for us and animals as it would have had for plants, however we kept it. And also, thiss mutation would have been very ssmall to begin with, and we have mutations in todays society. But the scale for this mutation must have been enourmous across the board of living organisms for it to have actually turned into such an important evolutionary feature. Sure small mutations like colours or the forming of bones, but senses? These are hard wired features of an organism that had to have come from somewhere but that would have sstarted out so primitive that for survival would have been rejected at that stage in development.

:confused::rolleyes:

Link to comment
Share on other sites

You really need to stop thinking that organisms can somehow "decide" or "choose" how they evolve. They don't. Random mutations that are advantageous in one way or another build up over time. Let's take sight as an example.

 

The origins of sight lie in sensitivity to light. Unicellular photosynthetic organisms often have eyepots, light sensitive cells that tell the organism to move toward the source so they can photosynthesize. It's very likely that something similar also occurred in evolutionary history. So even this very rudimentary version of sight can be beneficial. You may ask, so why can't plants see? Well in some ways, some can. They can bend their stems and leaves to follow the sun as it crosses the sky. But as said before by Macroscopic, not much more than this is needed for modern plants, as sun is their major energy source and they don't otherwise move.

 

But it is also advantageous for heterotrophic (organisms that get their energy by ingesting exterior organic material - aka, eating stuff) unicellular organisms to be sensitive to and move towards light as well - because that's where the photosynthetic organisms will be that they can eat. Again, even a simple version of sight can be advantageous. So what about another small improvement? perhaps being able to note when a dark patch moves through the light will allow these heterotrophs to move toward that dark patch as being a likely prey item. Simple but still advantageous. So sight develops, not because an organism "decides" to do so, but because those organisms with slightly better sight can find their food more easily and eat more, thus reproducing better/faster than those with slightly worse sight. Add billions of years and millions of mutations and you end up with sight as it is today.

Link to comment
Share on other sites

If you follow the history of evolution all animals and plants once originated as single celled organisms and have evolved to adapt to their surroundings. But how did these original cells have the genetics or brains to come up with these adaptations?

For instance, fair enough that original single cells evolved feelers to grab onto their surroundings, this could have been acheived through mutation. But how does an organism learn that it can view the world on a whole new level through sight and create powerful eyes?

 

First, let's get rid of that idea of "learn". And stop applying evolution to a single "organism"

 

Evolution happens to populations. I can't emphasize that enough. The individual doesn't have any conscious input into evolution. An individual is either lucky or unlucky enough to be born with the alleles (forms of genes) it is born with. If those alleles give it an advantage in the struggle for existence, the individual will do find and have lots of offspring. If not, too bad.

 

An individual did not "learn" that it can see. Instead, a lucky individual had a mutation in a protein that conferred the ability to detect light. "In the land of the blind, the one-eyed man is king". That ability gave an advantage of this individual over all the other individuals of its species. Over a period of generations, every individual was descended from the lucky one and had the ability to detect light.

 

Adaptations come about thru natural selection.

 

At what stage were any parts of a single cell, such as the normal parts of a cell able to presume that light could be seen and what parts started utilising it? What posssible advantage would an original cell, or even a even multi-celled organism gain from viewing surroundings, and how did the cell think to create a way to veiw them.

 

Again, the cell did NOT "think to create". There is no input or conscious decision on the part of the individual in natural selection. The advantage is obvious: an individual that can sense light and its surroundings, however dimly, can avoid danger or find food better than an individual without the ability.

 

With eyes the answer is known. The protein that detects light is rhodopsin, which makes up the light sensitive spot on the single-celled Paramecium. The gene Pax-6 regulate the production of rhodopsin and has evolved to direct the evolution of the eye by controlling the expression of the genes that code for the construction of the eye.

 

It just seems to unlikely that this could happen, even over thousands of millions of years. And even if it could, surely plants would have utilised sight too.

 

Sight gives no advantage to plants. After all, they can't avoid herbivores (predators). They also make their own food. Animals have to get food from others.

 

Natural selection is a means of cutting down odds. It does so by breaking up the formation of an organ into many, many steps and then ensuring that those steps will happen because only by having the step can the individual be the "winner" in the struggle for existence.

 

Here is a simplified example of how natural selection -- cumulative selection -- cuts down odds:

 

 

You have a 1 in 1024 chance of correctly winning 10 coin tosses in a row. But I can guarantee you I can find someone who can do so. How? Simple, use cumulative selection in the form of a single elimination tournament. I start with 1024 people and pair them up. Then each pair tosses a coin. The 512 winners are selected to go to the next round. Again they are paired and do a coin toss; the 256 winners are selected to go to the next round. Repeat this 7 more times. Now you have 2 people who have won 9 coin tosses in a row. The winner of this round has won 10 coin tosses in a row. And it is a certainty that such a person will be found with this method. We have taken odds of 1 in 1024 and converted that into virtual certainty. Now, I don't know which individual will win the tosses, but it is certain that one of them will, given the algorithm of the competition. Evolution by natural selection is a competition algorithm, more complex but analogous to the single elimination tournament algorithm.

 

This kind of problem can be seen in most of the other extreme senses as well. It would be great to know if there was a theory out there.

 

The theory is natural selection. Here is Darwin's summary of it:

 

"If, during the long course of ages and under varying conditions of life, organic beings vary at all in the several parts of their organization, and I think this cannot be disputed; if there be, owing to the high geometric powers of increase of each species, at some age, season, or year, a severe struggle for life, and this certainly cannot be disputed; then, considering the infinite complexity of the relations of all organic beings to each other and to their conditions of existence, causing an infinite diversity in structure, constitution, and habits, to be advantageous to them, I think it would be a most extraordinary fact if no variation ever had occurred useful to each beings welfare, in the same way as so many variations have occured useful to man. But if variations useful to any organic being do occur, assuredly individuals thus characterized will have the best chance of being preserved in the struggle for life; and from the strong principle of inheritance they will will tend to produce offspring similarly characterized. This principle of preservation, I have called, for the sake of brevity, Natural Selection." [Origin, p 127 6th ed.]

Link to comment
Share on other sites

Ok eventually evolution does cover all. But how does an organism decide to keep sight on the basis that the first mutation must have been pretty poor?

 

Let me reinforce Paralith: the organism does NOT "decide". Instead, however "poor" in overall quality the first mutation that gave rhodopsin was, having rhodopsin was better than not having it at all. Under those conditions, the equations of Mendelian inheritance are very clear: the allele will spread from generation to generation such that EVERYONE in the population will have it. The math says that this can't be stopped short of a major disaster to the population that kills (for other reasons) every individual that has the allele.

 

The visibility wouldn't have been helpful at all, if even achievable.

 

That is a false premise. Even being able to detect light vs dark would help a single celled organism: it helps keep the organism near the surface instead of going too deep where there is not going to be any food. Just "go to the light".

 

And also, thiss mutation would have been very ssmall to begin with, and we have mutations in todays society. But the scale for this mutation must have been enourmous

 

Yes, we have mutations. Many of them are beneficial. But no, the scale did NOT have to be "enormous". Each step can be quite small.

 

I highly recommend Richard Dawkins Climbing Mt. Improbable because he looks at this specific example: evolution of eyes.

 

across the board of living organisms

 

Another false premise. It is NOT "across the board". It is in ONE species. However, because the individuals in that species do well, eventually all species are going to be descended from that species by "descent with modification". Species that did not evolve eyes in environments where they would be advantageous are going to go extinct.

Link to comment
Share on other sites

Well eyes could have evolved only once in the evolutionary history in the form of Pax-6 gene as mentioned earlier. Plants do show phototropism they do this with the help of a protein called NPH1.

 

Who said that half an eye is useless? The sight not only help in search of food but it also help in search of mates. A wonderful example is the Glow-worms I can see plenty of them glowing in my backyard and here how it works.

 

In female glow-worms a greenish-yellow light glows on the underside of the body at the tip of the abdomen they do this with the help of two compounds called luciferin and luciferase. The females glow at night and you can't find them in the morning and they are sedentary. The female twist her abdomen so that the light can be visible above. The male has the ability to fly and has a good sight and if he finds a female he will just fall and mates with the female.

 

Well I saw these worms for a couple of days in my backyard but suddenly they all vanished and I couldn`t find them till now. Are these worms seasonal can any one tell me when can I find them.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.