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Re: Annual Review of Physiology papers



----- Original Message -----
From: "Jaime A. Headden" <qilongia@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Tuesday, November 28, 2000 9:04 AM
Subject: Annual Review of Physiology papers

[snip]

> By the
> late Permian, evolution of decompositional microbial and fungal
> communities, together with disequilibrium in rates of carbon
> deposition, gradually reduced oxygen concentrations to values possibly
> as low as 15%.

What -- 15 %? Some have suggested that during the P/T-extinction oxygen
levels halved, but I can barely imagine this happening by normal activities
of life. Have any strange features of e. g. tetrapod rib cages from that
time been noticed?

> Also, perhaps overlooked, but relevant:
>
> Farmer, C.G. 1999. Evolution of the Vertebrate Cardio-Pulmonary System.
> Annual Review of Physiology 61: 573-592.
>
>   Vertebrate lungs have long been thought to have evolved in fishes
> largely as an adaptation for life in hypoxic water. This view overlooks
> the possibility that lungs may have functioned to supply the heart with
> oxygen and may continue to serve this function in extant fishes. The
> myocardium of most vertebrates is avascular and obtains oxygen from
> luminal blood. Because oxygen-rich pulmonary blood  mixes with
> oxygen-poor systemic blood before entering the heart of air-breathing
> fishes, lung ventilation may supply the myocardium with oxygen and
> expand aerobic exercise capabilities. Although sustained exercise in
> tetrapods is facilitated by septation of the heart and the formation of
> a dual pressure system, a divided cardio-pulmonary system may conflict
> with myocardial oxygenation because the right side of the heart is
> isolated from pulmonary oxygen. This may have contributed to the
> evolution of the coronary circulation.

Wonderful idea, but older than that:
Carl Zimmer: _At the Water's Edge. Macroevolution and the Transformation of
Life_, The Free Press (division of Simon & Schuster Inc.) 1997
Mentions that you can chase a salmon to death because the blood from the
gills gets into the heart last, but apparently not an _Amia_, that the first
sarcopterygians are known from open sea sediments and similar things. (Well,
I'm not sure it's a salmon in the text, I only have the German translation
which has a _Diadectes_ and a _Mixosaurus_ by Spinar & Burian as title
illustrations, both animals that are not mentioned in the book, and a title
that *urgh* retranslates as "The source of life. Of Darwin, dinos and
dolphins". Only movie title translations are worse.)