fuck you did it again

Fooly Cooly never dies.

Allow me to present a very simple argument by analogy.

Life exists to reproduce. In other words to pass on DNA, or genetic material. Go back to the fundamentals of life. What makes an organism 'living'? Few requirements are the ability to gather resources and pass on genetic materials to offsprings.

How do single celled organisms reproduce? The most well known and understood by common people is fission, or division into 2 'identical' daughter cells (note that this statement is not 100% correct)
There are 2 possible cases.
1) Cell is successful: produces offsprings and pass on genetic material
2) Cell is unsuccessful: does not produce offsprings

How do sexual organisms reproduce? by combining genetical materials from two organisms, thus passing genetic material onto a single offspring.
Again, there are two cases.
1) Successful: produces offspring and pass on genetic material
2) unsuccessful: does not produce offspings.


Now, the question that is still not clearly answered is why do multi-cellular organisms "die"?
First of all, one must define what this "death" means.
For the typical single cell organism, they no longer exist after fission, because DNA is semi-conserved and passed onto the offsprings. In a way, the parent cell dies. There are also cases where bacterias produce daughter cells inside there plasma member and the mature daughter cells will lyse (break open) the mother cell, killing it.
For the typical multicellular organism, death occurs when the organs can no long function properly.

Now, with that in mind, lets explain why "death" is an very important evolution step for the multicellular organisms.
I will explain this in the simplest way- an ecological view point.

1) Evolution occurs because the environment is always changing. Species that mutant and acquire different traits may have a better survival chance if the environment changes (biotic AND abiotic conditions)
2) There is a limited amount of resource in the environment. Nothing is unlimited.
3) Take a successful competitive species such as humans. If the human ancestors did not evolve "death", what would happen? Population explosion. There will not be niches available for offsprings (imagine if no one died, what would happen to the limited resources and space on earth?)
4) Because there are no niches available for the offsprings, all of them will 'die' off (this is a different form of death, from not being able to acquire food and shelter)
5) evolution does not take place. DNA will be conserved from year 0 to billions of years after.
6) However, the environment changes all the time. If there is no evolution, the competitive species will not be able to survive (out compete others) when conditions change
7) over time, these species of organisms who do not have the "old age death" trait will automatically face extinction.


tl;dr
Death IS an very good evolution, it's not a bad trait at all.


more ranting....
Single cell organisms that do not "die". Are they really better off than those that do "die"?

take a strain of bacteria. They will grow until they reach a carrying capacity (in this case, cells die because of a lack of resources of some kind). In this saturated environment, what is the condition of the allele pool? Probably all genes from the most successful bacterias, which are basically the same, there is no variation (because the ones that do vary are bad competitors in the current environment).
Now what happens if you change the environment?
Every cell dies. Species goes extinct.
In a way death makes sure that there will always be new niches available for offsprings, enough for variations to accumulate, to ensure the whole species' success.

fuck yeah. I'm so ready for my finals

This post was edited by Exx on Dec 8 2011 11:08pm

Good answers so far. The thing to keep in mind is that evolution has no purpose or goal in mind.

Evolution happens through random changes that end up improving rates of survival and reproduction. Our current life-spans just happen to be the best alternative compared to whatever other options there were since man first evolved.

Maybe someday if environmental pressures change to make the longer-lived people more likely to reproduce, people will end up having on average longer life spans. Otherwise, death makes our societies more likely to survive, as a whole.

Also, when you compare organisms like us to single celled organisms, you have to take into consideration exponentially how many more chemical/hormonal/maintenance interactions that go on to determine our life span. All single cells have to do is eat, process chemicals, excrete, divide, repeat, and sometimes not even all of those. Our story is a little more complex and life span would require a vast amount of changes to affect because of the countess factors involved. Microbes evolve much quicker as well since they can reproduce every 20 minutes or so.

And to reiterate, Fooly Cooly never dies!!

its dawkins selfish gene

the view being that as genes are passed to offspring , there is less evolutionary need for the parent to survive to pass on its genes , as the offspring take up the evoltionary need to reproduce
sexual reproduction could be called the villain here , as it's really around this time that a strategy allowing a degrading body becomes feasible

then theres the idea that if the body is reverted to an embryonic or developing stage , it can develop all over again , and again , and never die

http://green.yahoo.com/blog/guest_bloggers/26/the-world-s-only-immortal-animal.html

This post was edited by Matao on Dec 9 2011 03:54am

A lot of it has to do with the carrying capacity of an environment. There are plenty of other factors (disease, extinction events, etc) that drive death.

People have also included telomere and apoptosis into this thread, which is pretty clutch.

Cell death is required to form some of a creatures more distinguishing features. Take, for example, the feet of a chicken and a duck. They both have the same types of feet in development, but, thanks to apoptosis, a chicken will not develop webbed feet, whereas a ducks cells will continue to grow this feature. Environment, resources, and natural selection are the driving forces behind what features an organism will keep or inherent with time and what cells will undergo apoptosis during development.

Also, I think it's been said, but single cell organisms in fact die on massive scales every day. This includes age and disease (virus/bacteria/some protists).

Finally, death has always been a part of life. Death goes alllll the way back to when the earth was inhospitable and the only living things were extremeophiles.

Death is necessary for evolution and a healthy ecosystem. Otherwise there is overpopulation, and organisms that have beneficial mutations would be starved of resources by those without it

Clearly.

Why do you keep saying "an very" ?