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I just dont understand...

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I just dont understand...

Postby rohith003 » Sun Feb 07, 2010 8:26 am

My name is Rohith.I am a 16 years boy from India.
MY doubt-
If we take tapeworm belonging to cestoda {platyhelminthes}...it requires a human and pig. So Human and pig belongs to chordata Which is highly evolved. So If we take evolutionary classification into consideration Platyhelminthes follows annelid, arthropods, Molluscs, echinodermata and finally chordata! If that is what evolution of animals... How did tapeworm existed till now with out either man or pig! Is it a modification of some other planarians{Turbellaria} or some fluke{trematoda}!
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Postby JackBean » Sun Feb 07, 2010 9:39 am

the parazites can of course evolve just after they find appropriate host. Maybe in the past, they could use other hosts and in evolution they changed to human/pig
http://www.biolib.cz/en/main/

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Re: I just dont understand...

Postby rohith003 » Sun Feb 07, 2010 10:51 am

But an evolutionary change is a very very late process. It takes some 1000s of years for the next phyla to come into existence! If we think the time when only platyhelmenthis is present...1st tubellarians then trematoda and finally cestoda! And the following phyla is nematoda. How can trematoda{its larva is ectoparasite on fishes} and cestoda{endoparasites on vertebrates} really existed lived for so many years!
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Postby JackBean » Sun Feb 07, 2010 11:09 am

I'm telling you, that they weren't parasites since they evolved.
http://www.biolib.cz/en/main/

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Re: I just dont understand...

Postby rohith003 » Sun Feb 07, 2010 11:12 am

So what are they then! i am not just saying they must be parasites but they need some vertebrate to live! A man and a pig! for perpetuation!
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Postby JackBean » Sun Feb 07, 2010 11:45 am

They need it now, but when they separated as some sort of phyla, they were just some worms and later they found out, that it's fine t be parasite.
You're assuming, that once a species evolved millions of years ago, it didn't evolve at all, but it was evolving all the time of course.
http://www.biolib.cz/en/main/

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Re: I just dont understand...

Postby rohith003 » Sun Feb 07, 2010 12:58 pm

so yu say its modification incourse of evolution? and there is only one thing coming under platyhelminthes?
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Postby JackBean » Sun Feb 07, 2010 2:32 pm

Sorry, I don't understand
http://www.biolib.cz/en/main/

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Postby jwalin » Sun Feb 07, 2010 4:25 pm

rohit i didn't understand your last post

but jackbean is very right in saying evolution isn't a sudden change it's a modification that takes place continuosly over a long period of time

at some point of time the worms may have gottten into the vertebrates. and maybe of the many that got into the vertebrate one could have possibly devoloped some mechanism where it could feed on the vertebrate and selection pressures favoured it. it could be a result of mutation also.
the vertebrates live long and the worms could take a good advantage. the mutation would have got well established into its genes
and maybe when the organism was dying it could be infected by thousands of worms and a few of them could have been transferred to others maybe after the death or while the organism was living....
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Re: I just dont understand...

Postby rohith003 » Mon Feb 08, 2010 6:19 am

so yo say one of the very primary polychites are modified into tapeworm or flukes or what ever after the chordates came into existence!
IF THAT IS WHAT YU AFRE SAYING THEN WHAT ABOUT NEMATODA.
Did nematodes also evolved after tapeworm?
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Re: I just dont understand...

Postby robsabba » Mon Feb 08, 2010 4:52 pm

rohith003 wrote:so yo say one of the very primary polychites are modified into tapeworm or flukes or what ever after the chordates came into existence!
IF THAT IS WHAT YU AFRE SAYING THEN WHAT ABOUT NEMATODA.
Did nematodes also evolved after tapeworm?

There are plenty of non-parasitic nematodes. They live in the soil... I have seen them under the mircoscope. They don't need a host. Some parasitize the roots of plants, such as potato.
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Postby Darby » Tue Feb 09, 2010 3:15 am

Why couldn't ancestral cestodes infest ancestral vertebrates / chordates?
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