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Author Topic:   What IS reproduction?
RAZD
Member (Idle past 1405 days)
Posts: 20714
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Joined: 03-14-2004


Message 1 of 2 (560495)
05-15-2010 3:15 PM


I'd like to bring together parts of three current threads and look at one aspect that pertains to each of them.
First we have Are there evolutionary reasons for reproduction?:
quote:
MrQ Message 1
The question is in all texts of evolution life correlates to reproduction and reproduction is a key driving force in the evolution process. ... I mean, reproduction is very energy consuming process. ... if we assume the life came from organic molecules in the earth atmosphere or in a primordial soup, why on earth should a molecule suddenly decide to reproduce ...
Then from Definition of Life
quote:
RAZD Message 69
See wikipedia
Life - Wikipedia
particularly the "conventional definition
Life - Wikipedia
While there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life exhibits the following phenomena:
1. Organization - Living things are composed of one or more cells, which are the basic units of life.
2. Metabolism - Metabolism produces energy by converting nonliving material into cellular components (synthesis) and decomposing organic matter (catalysis). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
3. Growth - Growth results from a higher rate of synthesis than catalysis. A growing organism increases in size in all of its parts, rather than simply accumulating matter. The particular species begins to multiply and expand as the evolution continues to flourish.
4. Adaptation - Adaptation is the accommodation of a living organism to its environment. It is fundamental to the process of evolution and is determined by the organism's heredity as well as the composition of metabolized substances, and external factors present.
5. Response to stimuli - A response can take many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. A response is often expressed by motion: the leaves of a plant turning toward the sun or an animal chasing its prey.
6. Reproduction - The division of one cell to form two new cells is reproduction. Usually the term is applied to the production of a new individual (either asexually, from a single parent organism, or sexually, from at least two differing parent organisms), although strictly speaking it also describes the production of new cells in the process of growth.
(bold in the original)

(note the second wiki link above works, but it takes you to the same place as the first wiki link and should be replaced by
Life - Wikipedia)
and
quote:
Mr Jack Message 70
The trouble with any definition of life that includes reproduction is that excludes the many examples of things we'd call alive but don't reproduce: the sterile, the elderly and the unlucky. So you end up having to be rub in a side order of "potential to reproduce" or "from a class that reproduces" which again muddy the issue and, even then, reproduction is, itself, not exactly a trivial concept to clearly define.
And finally from Self-sustained Replication of an RNA Enzyme
quote:
dcarraher Message 39
A Living Cell, on the other hand, has ... information contained in its DNA - e.g. how to build a protein. The ability to build a copy of itself is not a characteristic of its physical binding chemistry, it is a process that requires messengers and translators. Replicating RNA replicates because of its chemical characteristics, not because of the information it contains that can be interpreted.
Noting that dcarraher apparently draws a distinction (whether it is valid or not) between DNA replication and RNA replication, it seems appropriate to delve into this in a little greater detail.
He also says:
quote:
Message 30
Because the experiment starts with something that is clearly non-life, and ends with more of something that is not significantly different. You started with the ability to replicate, and ended with the ability to replicate - you did not add the ability to replicate, nor did you add any other "life-like" characteristics. Ergo, irrelevant to the question of abiogenesis.
Now of course the point of the thread is that the RNA is self-replicating rather than just being replicated within a cell as part of the process of reproduction
Is this self-replication life? Without a clear definition of life it is difficult to say. Is a virus alive? This depends on your definition of life.
Is this self-replication a feature of life as we know it? Yes, it is common to all organisms during reproduction that all the elements of a cell are replicated.
Reproduction is commonly listed as an element of life, as seen in the wiki article above, and a critical part of reproduction is the replication of the material within a cell so that another cell is formed.
At its most basic level, cell reproduction occurs by:
  1. the accumulation of additional basic cell materials (the "structural" parts of the cell), and
  2. self-replication of the core molecules, the DNA.
This holds for prokaryotes and eukaryotes, for single cell life and multi-cellular life, for asexual reproduction and the reproduction of cells within sexual organisms.
As such, I would propose that self-replication of the core molecules is a better defining feature of life than reproduction.
Enjoy.

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AdminSlev
Member (Idle past 4641 days)
Posts: 113
Joined: 03-28-2010


Message 2 of 2 (560552)
05-16-2010 12:01 AM


Thread Copied to Miscellaneous Topics in Creation/Evolution Forum
Thread copied to the What IS reproduction?IS[/i] reproduction? thread in the Creation/Evolution Miscellany forum, this copy of the thread has been closed.

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