April 17th, 2009, 11:08 AM
what is it about a living thing that causes that tendency to die? I lack the biological education to answer that question in an argument in the religion subforum, so if someone can please give me an explanation I would most appreciative. Please and thank you
I hope to die first and then decompose, but no guarantees I suppose.Why does an organism decompose and die
more, why does our body degrade to the point that we die(applied to any organism). The brain goes through processes where it bits and pieces breakdown over time, same with all other parts of the body, degenerative conditions and whatnot, cause the body to eventually die. I'm curious about the biological process, the explanation for this.
Here's the thread in religion that I'm referring to.
April 17th, 2009, 11:52 AM
It's a requirement of evolution- for variation and adaptation over time to work, you have to create a new generation and the old one needs to die off so that they're not competing for resources. If you're going to have reproduction, you have to have death. Since reproduction is the only way to introduce sufficient variation for survival over geological time, we die.Originally Posted by Arcane_Mathamatition
April 17th, 2009, 11:55 AM
That is a big part of it there is also the build up of free radicals in our bodies that degrade things. There is various types of programmed cell death within our body. DNA degrades through recombination, splicing etc. I am pretty sure that there also a suite of genes that are used for cell degeneration and aging.It's a requirement of evolution- for variation and adaptation over time to work, you have to create a new generation and the old one needs to die off so that they're not competing for resources. If you're going to have reproduction, you have to have death. Since reproduction is the only way to introduce sufficient variation for survival over geological time, we die.
One of the people I know who works on aging thinks it may actually be an adaptive response. Over time, maintaining your body becomes more and more expensive, as you go through the wear and tear of life, as metabolic wastes build up, as free radicals build up, etc etc. This is the cost of life. Also as time goes on, how much we are able to benefit our reproductive success declines as well, especially with our increasing frailty from all the above-described affects. Eventually the costs of maintenance outweigh how much benefit we are capable of getting from enhancing our reproductive success - and we die.
April 17th, 2009, 12:11 PM
this much I understood, my question was aimed more on the individual scale, for one organism, the processes that cause it to die, (of natural causes, of course) I have the rudimentary understanding from high school Bio, it's just specifics that I'm really curious about, being that I don't have the background (I must admit, Bio was really messy when I learned it, and it just made me go bleh...It's a requirement of evolution- for variation and adaptation over time to work, you have to create a new generation and the old one needs to die off so that they're not competing for resources. If you're going to have reproduction, you have to have death. Since reproduction is the only way to introduce sufficient variation for survival over geological time, we die.) to answer the question and I don't know what to look for in a research question. rarely do you get exactly what you want when you research a specific question.
the question that was posed was why would death happen if not for God to start it, and I'm looking to get a secular biological explanation that doesn't require God in the answer, just to explain my premise for bringing the topic here.
Thank you, but, if you could be a little more... thorough... with the description on the process by witch the free radicals build up, and be slightly more layman, it would really help. Thanks though, dickies.
April 17th, 2009, 01:06 PM
Without death there is no evolution.
Obviously evolution makes organisms more successful.
again, the explanation behind death, not just what it is useful for.
April 17th, 2009, 01:30 PM
All generally true but these are mechanisms by which ageing occurs, not a "reason" for it as such.That is a big part of it there is also the build up of free radicals in our bodies that degrade things. There is various types of programmed cell death within our body. DNA degrades through recombination, splicing etc. I am pretty sure that there also a suite of genes that are used for cell degeneration and aging.It's a requirement of evolution- for variation and adaptation over time to work, you have to create a new generation and the old one needs to die off so that they're not competing for resources. If you're going to have reproduction, you have to have death. Since reproduction is the only way to introduce sufficient variation for survival over geological time, we die.
Arcane, I'm not sure what you're looking for. The responses you've gotten in this thread really cover what aging is all about. Our bodies get beat up by use, injury, disease, and stress, and at one point it's no longer worth trying to fight the tide and stay alive. What more are you looking for?
We die because otherwise there wouldn't be space for our progeny. That's useful.
Life doesn't work on the scale of individual organisms, which is perhaps where you're struggling. We don't benefit from our deaths, our genes do. For us to survive indefinitely places our progeny at risk due to competition. If we live indefinitely and remove reproduction, it means that our genes have no opportunity mutate or to recombine with other genes so that their vessel, the organism, may adapt to a dynamic environment.
Life doesn't, but natural selection does. I've been thinking about this a bit; this idea seems sound in principle but I wonder how it would work out in practice. For an individual's genes (in their offspring) to suffer from their prolonged lifespan would require that the individual's presence has a direct impact on how its own offspring do, and those offspring should do worse than offspring of an individual who died earlier. But regardless of who sired who, more individuals in the population means more competition, so the offspring of both individuals would both be affected negatively by the presence of the individual with the long lifespan. This seems to lend itself to a group selection argument, because on a whole groups with extra members hanging around, no matter whose parents they are, suffer from greater competition.
I will admit I have something of a bias against group selection (that phrase is like a bad word at my alma mater), but evidence for it actually occurring in nature is slim to none, from what I know.
My question was mostly answered in your first post paralith, it's the mechanisms behind aging that I was looking for, I suppose... still not exactly sure, to be honest. I guess the big ideals I am looking for is the reasons, mechanisms, and other processes that cause us to age, whither, and inevitably die, as organisms. The process and benefits of evolution aside, at the moment I only care about the individual.
You could also look at the question from the perspective of a physicist: entropy and the 2nd law of thermodynamics.
Any individual organism is shaped by an evolutionary history, Arcane. It is impossible to put "evolution aside."
It's not really a good explanation. Most animals are dead before they reach a stage of elderly incompetence.
This kind of explanation must lie in the middle. Animals wear themselves out to have a higher reproductive success. AND the consequence of this might be that there are reduced functions with age. They don't age because things start breaking down. That is aging.
to be fair spurious, that was true of humans up until a few hundred years ago, as well.
But, aging itself is not a function of evolution, it just happens that it leads to evolution through the reproductive process, and I realize that it is a point of life to further reproduce and continue ones genetic 'line.' It is, more likely, a "goal" of the organism to reproduce successfully. I am most curious not about that aspect, but more about how the organism's body ages, which, I assume, doesn't depend on the evolutionary line of said organism. I may be wrong, but I'm not sure that it's specifically the evolution aspect that I'm interested in, it's more the aging process from the biological perspective.
That's a good point, and that's why I think discussions of aging are probably limited to organisms who have been selected to live long lives and have a reasonable expectation of dying of old age. Humans are one of these, and it's not necessarily true that we died long before we aged in our evolutionary past - some hunter gatherers (not acculturated and without modern medicine etc) often live into their 60's and 70's. And yes, I agree, aging is the breakdown, but it can be accompanied by decreasing efforts to repair what's broken.
As I discussed above, in some species I think aging really is a function of evolution. In others, as spurious pointed out, death is likely to hit you long before you start to break down - in those species, aging never really happens. But humans - we've evolved to live longer lives than any of the other great apes, we're intelligent and we take care of each other, and the potential to just keep on goin is there.
If you're interested in the damage the body accumulates, then yes, every organism experiences physical insults of various kinds over their lives. When it comes to aging, the question becomes, how much energy/resources do we want to consume to fix ourselves, how much energy/resources are we capable of getting in our increasingly damaged state, how much do we want to take from our children for our maintenance when they could be giving it to their children? Etc.
But isn't it so that DNA has mechanisms that fix broken sequences? I think I might have read that these mechanisms are specifically imperfect, that is, evolved to be imperfect and that analogues exist that are perfect, mostly in certain species of bacteria?
Anyway, could it be that aging developed in apex animals early on and then filtered to all (most?) animals as evolution constantly changed the species at the top? This would probably have happened pretty quickly, as immortal apex animals would quickly deplete its own food source and thereby give another organism/s the new spot etc?
We have mechanisms to catch errors in DNA copying, of course, but within an entire complex organism (consisting of billions of cells) over a very long lifespan, even the tiniest inefficiency in those mechanisms will over time allow errors to build up. And I don't think I've heard that bacteria have better fixing mechanisms, but that they in fact have worse fixing mechanisms - they want more mutations to be more adaptable to their highly plastic environment.
Again, this is a group selection argument - some species ate themselves out of existence while other species conserved and survived. There isn't much evidence to suggest this process happens very often in the natural world. The problem with a species where all the individuals hold back is that, when an individual invades/mutates to be selfish, that individual will have more offspring than all the others, and eventually its genes will win out in the population. For group selection to work, you need groups isolated enough where selfish individuals don't migrate in very much and the rate at which selfish groups go entirely extinct needs to be very fast.Anyway, could it be that aging developed in apex animals early on and then filtered to all (most?) animals as evolution constantly changed the species at the top? This would probably have happened pretty quickly, as immortal apex animals would quickly deplete its own food source and thereby give another organism/s the new spot etc?
Also, consider what you call "apex" animals. Do most predators live long lives and die of old age like humans, or do they die before they age like most animals do? For many predators, if you ever get a serious injury, then you can't feed yourself, and you die. If you ever get too sick to hunt, you don't get food, and you die. In humans, we can last through debilitation because others will feed us. I know some predators are more social than others, but I know of none that actually bring food to an injured group member.
I think there's some fundamental things going on with the aging process that are quite puzzling - to me, at least. There are some co-called power laws that are observed in nature wherein small animals live shorter, more frenetic lives, while larger animals live longer, slower lives. Plot the logs of life span and body size on a graph and you get a nice straight slope (roughly). Strangely, though, large and small organisms are composed of the same cell types that function in almost identical ways, yet the organisms those cells come from have vastly different life spans.
Why is a mouse doomed to 2 years of existence while an elephant gets the luxury of 70 years?
I'd say it has mostly to do with the required rate of metabolism. The smaller organisms are, the larger outer surface they have in relation to their volume. They lose heat faster, so they just have to have a faster metabolism to produce more heat faster. There is a simple equation for this, but I am not sure what it is.Why is a mouse doomed to 2 years of existence while an elephant gets the luxury of 70 years?
Smaller body size requires different metabolic rates a mouses heart is racing all day long to meet the needs while an elephant wanders around slowly slower heart rate slower metabolism. Smaller animals have higher metabolism to combat the high amount of heat loss that they have compared to larger mammals. thats just a few reasons though
Lifespan can be subject to natural selection just as much as anything else; that's kind of what I've been trying to say this whole time. If you are a small bodied animal, it takes a short amount of time for you to grow; the faster you grow, the faster you start reproducing, and you end up accomplishing a lot of reproduction in just two years. Animals in a niche where small bodies are good can live shorter lives and not lose much reproduction. On the other hand, large bodies, like an elephant, take a long time to grow - both in the womb and out. It takes many mice lifetimes before an elephant has grown enough to reproduce. To "catch up" on reproduction takes them longer. Animals in a niche where large bodies are better need longer lives in order to accomplish enough reproduction.
and yet, both of those animals have a general metabolic and heart rate that suits their needs, and, if I can be so bold as to make the assertion, causes their bodies to decay and degrade at different rates (i.e. their bodies are doing the same amount of "work" in those relative life spans relative to the size of their bodies(sorry for using relative so much)). I remember hearing about an elephant mouse, so named because the average number of heart beats they have in a full life is approximately the same as an elephant, am I right about that?
I've always found the longevity of birds to be remarkable, in the wild a budgie is unlikely to make it past 3-4 years old, but in captivity they can last 15-20 years. It's a major increase in average lifespan.
There has to be something else that is selected for, which also increases lifespan.
You have to be careful with this generalization, I believe it holds up with closely related species. However, you don't have to look far to find out that this isn't universally true. Tortoises and sea turtles are extremely long lived, parrots, some parasitic worms live 20-30 years, and etc.
Also, look at domestic dogs, the longest lived breeds are the smaller ones.
Selection on lifespan also involves predation risk. As a mouse, if lots of things are hunting you and you can't expect to live very long anyway because, sooner or later, something is gonna eat you - then you grow fast, reproduce fast, get everything done ASAP. But birds have significantly reduced predation risk for their body size because they can fly! They can afford to take extra time growing, to take longer to reproduce, because chances are good that a predator won't manage to catch them anytime soon.I've always found the longevity of birds to be remarkable, in the wild a budgie is unlikely to make it past 3-4 years old, but in captivity they can last 15-20 years. It's a major increase in average lifespan.
There has to be something else that is selected for, which also increases lifespan.
environment, the fact that in the wild the budgie has to fight for food, fight to not get eaten by bigger animals, and fight to mate where in captivity, those fight responses, the fear of death and the constant adrenaline and spiked heart rate are non-existent. I think, in the wild, the tole of life just acts as a massive stress and strain on body, where the heart beats more times in those 3 years, possibly by a large margin, and the body gets so much more strain that it wears out in those three years.
Compare it to professional athletes, their bodies (especially American-football players) are wasted before they are 40, the stress is just too much.
This is true, but many birds also tend to grow quickly, and reach maturity fairly rapidly, there is a very high predation risk for birds during early development.
Another interesting factor I briefly remember from an ecology course I took in my freshman year, is that birds tend to show constant predation risk relative to age, while mammals tend to become more susceptible to predation as they age.
http://www.stanford.edu/group/stanfo.../How_Long.html
http://www.springerlink.com/content/206414v63m31486x/
The paper from the second link, although it doesn't say it in the abstract, suggest that the mechanism responsible for longer life in birds despite higher metabolic rates could be do to the presence of uncoupling proteins that lower oxidative stress. Suggesting they are using the proton motive force to more directly generate heat, rather than ATP.
April 21st, 2009, 12:07 AM
You could also just as well ask the reverse question: what is it about a living thing that causes it to live?
And the nature of this question is immediately clear. It isn't biological per se (although it could be). It's more philosophical.
The refusal to accept any biological explanation to the first question suggests you are looking for a philosophical answer.
Any answer is ok in that case.
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