Redundancy

nozzferrahhtoo

Somewhat of a newbie question here but though I would pick some brains.

Something I read today got me thinking about how we use the word Redundancy in Biology. I find that I know what I mean by it but I find that I am not really able to spell it out in simple terms. One of those annoying words where I know what I mean when I use it but I do not know how to describe what I mean when I use it.

So how would you adumbrate the meaning of the word to someone you were trying to explain it to?

For me the best I can do is suggest that Redundant means something that, although present, does not actually add any function in and of itself except maybe for increased efficiency.

The obvious example of this would be kidneys. We have 2 but can live perfectly well with only one. The presence of a second increases the efficiency at which we can do the work kidneys do, but that is all. In other words, the presence of a second does not actually add any new utility or function (or does it?).

I would contrast this to eyes. Although we have 2 eyes the presence of the second DOES add function and so would not be "redundant" as such. Depth perception, judging distances and speeds of objects, 3D issues and more all benefit from a second eye.

So am I on the right track or not? Whether I am or not how would you explain what you do, and just as importantly do NOT, mean by the word, and would it be therefore right to say 2 kidneys is an example of redundancy but two eyes is not? How would, say, multiple limbs fit into this.

And what in this context would you say to someone who claimed that the ability to regrow limbs was somehow an example of "redundancy" as I read today which is what set me off on this thinking.... as for me it does not seem to fit at all.

Tree

I like to think of redundant tissue/organs as backups for when you've ruined the first one (or half of one as appropriate). Likewise the redundancy in the genetic code is handy for when you've messed up the code and there's a similar one lying around for the same amino acid \o/

Capt'n Midnight

We have binocular vision but many herbivores wouldn't, an extreme would be small song birds which can't see directly in front since their eyes are so far back.

Organs that are expensive to create and maintain would be selected against if there wasn't an advantage to them. Remember in the wild our kidneys and livers might have to cope with a lot worse than the sober of us would inflict on them nowadays.

nozzferrahhtoo

Thanks guys but not sure this is getting to the heart of my question. I know what redundancy is good for essentially. What I am asking is a little different which is how you would define redundancy itself in biology, and what would be examples of what you think fits the definition and what does not.

Is my definition above on track or entirely wrong, and if it is on track would I therefore be correct in calling 2 kidneys redundancy but not 2 eyes as the latter does something the former does not... which is add function.

Improbable

I would probably say something like: "something you can lose without a loss of function". Being able to regrow limbs does not fit into redundancy. So if you consider an inactive gene or a gene of which you have multiple copies, you could lose that and have no loss of function so I would consider that redundant. The muscle that cats for example use to swivel their ears. We have the same muscle but it's so weak that we can only wiggle our ears a bit. I would also consider that redundant. But like you said, even though we have 2 eyes, we would lose function without the 2nd one, depth perception etc. The same thing applies to hearing as 2 ears allow you to determine where a sound is coming from.

So yes, I'd agree with you.