Author Topic: How did parasites survive?  (Read 472 times)

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Offline One Above All

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How did parasites survive?
« on: October 19, 2012, 02:33:53 PM »
AFAIK most parasites kill their host. Without a host, they die as well. How did they evolve with such a flawed "design"?
I assume the fault is with my knowledge, but I'd still like an answer just to be sure.
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Offline Seppuku

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Re: How did parasites survive?
« Reply #1 on: October 19, 2012, 03:00:18 PM »
Interesting question, I don't have a definite answer, but it does seem to be a flaw. Most parasites I know of tend to keep their host alive rather than kill them off, like the parasite that replaces the tongue of a particular fish or different kinds of worms, including tape worm. At least I've not heard of these parasites killing their host.

I know there is a parasitic fungus that grows on insects and takes control over its nervous system to move it to a spot where a predator like a bird can eat it. This does seem pretty stupid, but the advantage for the fungus is that if a bird eats it, its able to spread itself once it becomes bird poop. I think there's also one that takes them to higher ground to spore. I am zombified and my brain isn't functioning, so I can't think of other examples I've seen in documentaries of where a parasite will kill its host.

But it may also be that the parasites needs more nutrients than its host can provide in order to stay alive. It's a guess, but flaws can happen because they've not fully adapted to the environment but have adapted enough to reproduce. You might view it as a transition period in their evolution or in their adaptation to their environment or like in the case of the above example, they really only need to reproduce - it fairly common in organisms that once they've reproduced or lost the ability to reproduce then they die, so it might not matter that they kill their host. Heck, the fact female humans live for many years past menopause is an anomaly, from what I understand it's something that doesn't happen very often in nature and it's a trait we share with whales too...assuming I've got my facts right there. That would be my educated guess on this one.
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Offline Graybeard

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Re: How did parasites survive?
« Reply #2 on: October 19, 2012, 03:16:09 PM »
That bothered me too.

There are two types of parasite[1]: the one that is (i) non-fatal and (ii) turns the host into an egg producing factory – e.g. tapeworms, and the ones that are fatal – e.g. some bacteria, fungi, etc.

It appears that tapeworms are in it for the long term but the bacteria, fungi, etc., turns themselves into thousands/millions of bacteria, fungi spores, etc. and are passed on ... but the host dies. In the latter case, all that has actually been lost is one bacterium/fungus spore.
 1. In fact there are more, some develop a symbiotic relationship
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Offline Nam

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Re: How did parasites survive?
« Reply #3 on: October 19, 2012, 04:51:59 PM »
I've always wondered if parasites could be considered intillegent? I mean, some of the things they do seem quite intillegent for, apparently, having no brain[1], or what not.

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 1. speaking about endoparasites; some parasitical plants, and other such parasitical forms.

Offline wright

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Re: How did parasites survive?
« Reply #4 on: October 19, 2012, 06:53:24 PM »
I've always wondered if parasites could be considered intillegent? I mean, some of the things they do seem quite intillegent for, apparently, having no brain[1], or what not.

-Nam
 1. speaking about endoparasites; some parasitical plants, and other such parasitical forms.

Maybe a better word to use would be successful, rather than intelligent? Parasites like tapeworms have evolved to coexist with their hosts more than the cordiceps fungus Seppuku mentioned, but both are clearly successful in their different strategies of host exploitation.
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Offline Nam

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Re: How did parasites survive?
« Reply #5 on: October 19, 2012, 07:03:15 PM »
Well, if you may consider some of the things they are capable of doing; I read something a year back by this scientist from the early 19th century; I forget his first name but I only remember his last name 'cause it's the same as mine, which is "Arnold". I don't remember everything he wrote, science isn't my topic in all seriousness[1] so I could be talking complete nonsense. And, if I am: I apologize--but he discovered this parasitical plant, I forget...Rafflesia or something. I don't know...I found it interesting, to a point.

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Offline Lectus

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Re: How did parasites survive?
« Reply #6 on: October 19, 2012, 09:06:55 PM »
It's the same as computer viruses.

They keep spreading silently while the computer still keeps working.

If they show up on purpose the user is more likely to format the hard disk or scan with an anti-virus.

So the parasites spread long enough for finding more hosts before the host gets wiped out.
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Offline Mooby

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Re: How did parasites survive?
« Reply #7 on: October 20, 2012, 11:22:17 PM »
Let's do a thought experiment.

You're a population of organisms that feed on fish.  Nom nom nom!

One day, you develop the ability to feed on a fish without killing it right away.  So instead of needing to look for a new fish to eat every day, you can use the same fish for 2-3 days before finding a new one.  Now you have an advantage when food gets scarce.

Over time, you get better and better at feeding on just one fish for a long time.  You get so good at it, that you start to gear your whole life cycle (birth, growth, maturation, reproduction) around having one fish to feed on your entire life.

Parasitism is simply a byproduct of using another organism as a resource so efficiently that one becomes completely dependent on that organism.
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Offline shnozzola

Re: How did parasites survive?
« Reply #8 on: October 21, 2012, 11:21:41 AM »
AFAIK most parasites kill their host. Without a host, they die as well. How did they evolve with such a flawed "design"?
I assume the fault is with my knowledge, but I'd still like an answer just to be sure.

One above all,
Here is somewhat of an answer.  Unfortunately still not free, from the newest New Yorker magazine.  It explores all the bacteria that has evolved with us, thought to be deadly to us for so long and now understood to possibly be totally necessary. Maybe as necessary as our DNA.

http://www.newyorker.com/reporting/2012/10/22/121022fa_fact_specter

In the article a doctor talks about a patient who had severe long lasting ear infections in one ear, and after they tried everything - antibiotics of every kind - then the patient  took ear wax out of the other ear, and the biome of bacteria that came with it solved the problem.  At the time the doctor thought it ridiculous, now knowing that the idea is important. Excellent article overall.

Here's another important link.

http://www.metahit.eu/index.php?id=234
« Last Edit: October 21, 2012, 11:34:52 AM by shnozzola »
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Offline Graybeard

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Re: How did parasites survive?
« Reply #9 on: October 21, 2012, 12:00:08 PM »
RELIGION, n. A daughter of Hope and Fear, explaining to Ignorance the nature of the Unknowable. Ambrose Bierce