Evolution Of Reproduction

[cfry]

So, to me, this is a burning question. How did reproduction evolve? If everything is just an accident, how would something like reproduction just "be" one day. Think of the first life on earth from an evolution perspective. So there are a lot of scientists that say "if life can happen, it will happen". That right there seems suspect to me. Why will life happen just because it can happen? I can have pizza tonight but that doesn't mean I WILL have pizza tonight. Anyway, so we have the first life that just happened to come about. Either that thing had to happen with the ability to reproduce, or else it would just die out. Are we to think that this thing just accidentally became alive AND also just so happens to be able to rip itself in half, still live, and then have a clone? Or maybe this first thing just happened to pop into existence with another thing AT THE SAME TIME which just so happens to have opposite sexual organs? Come on now. Reproduction is extremely complicated and wont work if anything is missing from the mix. So its not like reproduction would have any time at all to evolve. It better work right the first time or its all over for that organism. I'm not interested in reading some dry 100 page report on the subject. Just give me the 1 paragraph summary (if you have one). I realize that this is going to be nothing more than educated guesses but, maybe one angle will resonate better than the others.

[jeskill]

Reproduction is basically the act of producing a copy of an original. In order to have reproduction at the most basic level,

In fact, it's been hypothesized that reproduction started even more simply than that. The RNA World Hypothesis proposes that life began with RNA, which can both store and duplicate genetic information.

 

So to answer your question, "reproduction" didn't instantaneously appear as the complex chain of events that occurs in animals. It started off very simple as the reproduction of RNA and/or DNA and/or protein, plausibly in some primordial soup. Very slowly over billions of years, as organisms became more complex, evolving into single-celled organisms (e.g. bactera, archaea), then simple multi-cellular organisms (e.g. sea sponges), then complex multicellular organisms (e.g. worms and the rest, plants, fungi), reproduction became more complex.

 

Instead of asking the question, "how did reproduction evolve", you might want to consider the question, "How does reproduction allow evolution to occur?" Evolution is the change in certain traits over generations -- over time weeds evolve resistance to herbicides, bacteria evolve resistance to antibiotics, etc. Evolution can only occur if there's variation of a certain trait within a population. Variation, in turn, can only occur if the copying process (reproduction) makes mistakes.

 

Edit to say: someone posted this video about abiogenesis which explains some of the theories concerning how early early early life forms may have replicated.

Edited September 1, 2011 by jeskill

[granpa]

the first polymers formed by adding subunits to the ends.

this molecule could grow (like fire) but wasnt alive.

 

at some point nature selected for teh ability to reproduce along the sides of the molecule like rna.

(subunits that couldnt attack along the sides disappeared)

this molecule was then alive.

Edited September 1, 2011 by granpa

[Edtharan]

Have a look at this video: http://www.youtube.com/user/cdk007

 

It starts to talk about it at around 2:40.

 

Basically, there are natural systems that can reproduce. Crystals are one example. But the video talks about how lipid bi-layers can grow (by absorbing other lipids) and reproduce (due to mechanical forces - like from waves against rocks). It also talks about how nucleotide monomers can join together into nucleotide polymer chains and then form pair bonded chains. And, when environmental changes (typically temperature) occur, it can cause the pair boned chains to separate into the complimentary chains, and then reform a new pair bonded chain from nearby monomers (basically the changes in heat cause it to replicate).

 

This is the start of biological reproduction (it is not complete as it is driven by outside forces - variations in temperature), but any nucleotide sequence that increased the replication speed (as heat is not the only way they can be separated, they can use chemicals to do so) would reproduce more often and so have a larger population and take up more resources than the less quickly reproducing ones.

 

This allows a step by step process by shich an externally forced replication can beome an internally driven reproduction.

[the asinine cretin]

The emergence of the eukaryotic cell and sexual reproduction trip me out.

[allopoietic]

I think that life and biological evolution starts with the first complete cell roughly around four billion years ago. In my opinion, the energy environment on the surface of the Earth was too vigorous, and the time from the end of the terminal bombardment that formed the Earth too short for minerals to evolve something so complex as the first cell. Therefore the first cell was either an artifact of God or space aliens, or the initial evolution of minerals took place over billions of years in a space environment, perhaps to cold of the Oort cloud, and then the cell was transported to Earth via a comet or asteroid. The energy environment in the human body is so vigorous that each and every cell must do between a thousand and a million repairs to DNA each day. Cells all have systems that actively and vigorously defend the order that the cell has by automatically checking and repairing essential structures. Since minerals have none of that, I think a cold environment and more time would be the only hope that evolution can happen in minerals. The short answer is that we do not know where or how the first highly advanced systems that made the first cell came from, but once it was on the Earth, the cell pattern was programmed to defend itself, reproduce, and evolve in the energy environment of Earth.

[Moontanman]

I think that life and biological evolution starts with the first complete cell roughly around four billion years ago. In my opinion, the energy environment on the surface of the Earth was too vigorous, and the time from the end of the terminal bombardment that formed the Earth too short for minerals to evolve something so complex as the first cell. Therefore the first cell was either an artifact of God or space aliens, or the initial evolution of minerals took place over billions of years in a space environment, perhaps to cold of the Oort cloud, and then the cell was transported to Earth via a comet or asteroid. The energy environment in the human body is so vigorous that each and every cell must do between a thousand and a million repairs to DNA each day. Cells all have systems that actively and vigorously defend the order that the cell has by automatically checking and repairing essential structures. Since minerals have none of that, I think a cold environment and more time would be the only hope that evolution can happen in minerals. The short answer is that we do not know where or how the first highly advanced systems that made the first cell came from, but once it was on the Earth, the cell pattern was programmed to defend itself, reproduce, and evolve in the energy environment of Earth.

 

 

We might not know exactly how... yet... but we know enough that there is no need to invoke Gods or space aliens....

[kitkat]

Is is possible for the first cell to emerge come from the deep sea vents?

[Moontanman]

Is is possible for the first cell to emerge come from the deep sea vents?

 

 

There are some hypothesis's that go in that direction, personally if I had to predict i would say the beginning of life was a synergy of more than one process, quite possibly several, lots of good videos on you tube that cover possible avenues of abiogenics.

 

here is a good one...

 

http://www.youtube.com/user/potholer54#p/c/DB23537556D7AADB/3/v8nYTJf62sE

Edited October 31, 2011 by Moontanman