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Are there evolutionary reasons for reproduction?

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Author Topic:   Are there evolutionary reasons for reproduction?
Dr Jack
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From: Immigrant in the land of Deutsch
Joined: 07-14-2003
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Message 122 of 136 (577090)
08-27-2010 6:50 AM 		Reply to: Message 114 by dennis780
08-20-2010 10:59 PM

Re: Look Ma, no enzymes!
Why do you think oxygen is needed? It's widely thought that oxygen based metabolism didn't evolve until quite late in the history of life, sulfur-based metabolism (which still exists today) is a much more likely candidate for the metabolism of early life, but there are many other possibilities.
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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.4

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Message 128 of 136 (580544)
09-09-2010 8:10 PM 		Reply to: Message 123 by barbara
09-08-2010 4:04 PM

Re: Look Ma, no enzymes!
They did what all organisms do with their waste products, excreted them into the environment. Oxygen, conveniently is a gas and thus doesn't build up locally in the same way as most excreted toxins.
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Dr Jack
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Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.4

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Message 131 of 136 (581921)
09-18-2010 6:55 AM 		Reply to: Message 130 by barbara
09-18-2010 6:35 AM

Re: mammal placenta
New question: Did the retrovirus that form the placenta the same in all mammals that have a placenta?
​
That's not really on-topic here. Start a new thread if you want to ask more.
​
But, quickly: the placental mammals (eutheria) appear to all share the same gene derived from a retrovirus that is involved in placental formation. This implies that the insertion happened once for all placental mammals. Certain marsupials have very placenta like structures, that appear to be separately evolved; I do not know whether these share the same genetic basis.
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