Timeline for What is the evolutionary advantage with two lungs (kidneys)?
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
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| Jun 1, 2021 at 0:01 | comment | added | John | @Hans the heart starts as two unconnected blood vessels. this may help open.oregonstate.education/aandp/chapter/… I have a whole answer in the unclosed question about this. biology.stackexchange.com/questions/100928/… Your questions about bilateral symmetry are great questions I suggest asking them as a stack questions (look for identical questions first) but in short is comes down to shoving 30ft of digestive tract in 2 feet of torso and the fact we are no longer laterally narrow fish. | |
| May 31, 2021 at 23:27 | comment | added | Hans | @John: Wow, really? Does the heart start out as two bilaterally symmetrically embryonically? If so, my previous other question still remains: why do we not have equal number of people having left situated and right situated single-organ heart and bilaterally symmetrically situated two-organ heart? | |
| May 29, 2021 at 4:50 | comment | added | John | @Hans the heart actually starts as two sperate organs embryonically. the only organs that do not start as pairs are the digestive organs (stomach, liver, pancreas, spleen) because the digestive system starts as a single tube. | |
| Mar 7, 2021 at 22:48 | comment | added | Mike Serfas | The nodal signalling pathway is clearly involved, which can be traced back to the clockwise motion of cilia in some species. But I have not kept up with recent developments in this area; you should find more with a little research. | |
| Mar 7, 2021 at 18:40 | comment | added | Hans | randomly on either sides of the spine. | |
| Mar 7, 2021 at 18:36 | comment | added | Hans | As I said, "other organs" in plural, with spleen being but one example, which do not have bilateral symmetry. What is the mechanism of all the other non-bilateral symmetric organs? With respect to the spleen in particular, it just begs the question: what makes the stomach non-bilateral symmetric? You can say they just compete for the same spot and randomly eking out a space and deforming each other. Why do all of them not have two or more which can all be arranged bilaterally? Another question is why we do not have more equal distribution of people having their hearts and spleen situated | |
| Mar 7, 2021 at 17:45 | comment | added | jamesqf | Bilateral symmetry goes much further that the internal organs, of course, so bilateralism must be deeply embedded in the genes. (Even structures like vertebrae are symmetric.) So the question really should be why some few organs AREN'T paired or symmetric. | |
| Mar 7, 2021 at 14:11 | comment | added | Mike Serfas | Bilateral symmetry is of course an approximation - biology doesn't know theory. But it is a good one. For example, the spleen begins from the dorsal mesogastrium (the mesentery connected to the greater curvature of the stomach), making it, conceptually, an unpaired midline organ that merely reacts to surrounding circumstances. In some humans the situation is more bilateral | |
| Mar 7, 2021 at 9:20 | comment | added | Hans | -1. Your thesis does not stand. The heart and other organs like spleen does not have bilateral symmetry. | |
| Mar 6, 2021 at 18:58 | history | answered | Mike Serfas | CC BY-SA 4.0 |