An evolutionary race

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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An evolutionary race

Post by Lilly08 » Mon Apr 13, 2009 1:44 am

I have read my book but it does not seem to explain it very well.

Can this be summarised simply, because the book is giving a lot of discription and i am confused about the following.

How are pathogens and host locked in an evolutionary arm race?

Right this is what i understand as quickly as we evolve mechanisms to combat pathogens, they evolve new methods of overcoming our system.

What does this mean and why do the pathogens have an edge in this race?

How are they evolving very quickly?

I know its a lot to answer, but i would really appriciate if someone can explain this to me.

Thank you

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Post by plasmodesmata11 » Mon Apr 13, 2009 3:32 am

Pathogens evolve quicker because they reproduce quicker, which gives them the advantage. Hosts and pathogens aer constantly "fighting", like you said, and one is always trying to beat the other. When people create antibiotics, bacteria will survive and pass on their genes, making it so they can attack us more. In turn, we will fight them another way, maybe bacteriophages, and then natural selecton will pick the next set of genes to go on, etc. Same thing with us; the infectuous pathogens kill us off, leaving (in theory, and say this since medicine is so advanced) only the fittest genes.

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Re: An evolutionary race

Post by skeptic » Tue Apr 14, 2009 3:09 am

An important evolutionary direction for pathogens is the move to become less pathogenic. If a parasite kills its host, that is disadvantageous. Thus, parasites that do less harm to the host live longer and reproduce more successfully. This trend, towards less harm, is very common. Indeed, it often goes to the extent of a pathogen becoming advantageous to its host. Humans have many symbionts from this source. For example : gut bacteria which produce vitamins.

The ultimate in this evolutionary trend is towards incorporation. The human genome now carries a heap of genes that once were a part of assorted viruses. Retroviruses incorporate their genes into the nucleus of a cell. If the cell they do this to is a gamete precursor, the virus gene may end up in a sperm or ovum. If it becomes a new organism, the gene is then passed down indefinitely. We all, thus, have a heap of virus genes as part of our genetic make-up.

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Post by mith » Tue Apr 14, 2009 3:23 am

That's true, but for some, making us sneeze and cough is part of the reproductive strategy that cannot be altered without drastically reducing competitiveness.
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