Status: this preprint is currently under review for the journal BG.
Reply to Lars Olof Björn’s Comment on our article “Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum”
Karo Michaelian1and Aleksandar Simeonov2Karo Michaelian and Aleksandar SimeonovKaro Michaelian1and Aleksandar Simeonov2
1Department of Nuclear Physics and Application of Radiation, Instituto de Física, Universidad Nacional Autónoma de México, Circuito Interior de la Investigación Científica, Cuidad Universitaria, Cuidad de México, C.P. 04510
2Faculty of Natural Sciences and Mathematics, Ss. Cyril and Methodius University in Skopje, North Macedonia
1Department of Nuclear Physics and Application of Radiation, Instituto de Física, Universidad Nacional Autónoma de México, Circuito Interior de la Investigación Científica, Cuidad Universitaria, Cuidad de México, C.P. 04510
2Faculty of Natural Sciences and Mathematics, Ss. Cyril and Methodius University in Skopje, North Macedonia
Received: 27 Jul 2021 – Discussion started: 02 Feb 2022
Abstract. Lars Björn, in his critique of our article, doubts our assertion that at the origin of life the fundamental molecules of life (those in the three domains) were UVC pigments, dissipatively structured under a thermodynamic imperative to absorb and dissipate this UVC light into heat. Björn bases his critique on the suggestion that non-living material can be more photon absorbing than living material. He gives a number of examples in which he shows that the albedo of material devoid of life is lower than that of biotic material and concludes that these examples counter our assertion. However, Björn makes the erroneous assumption that albedo (reflection) is the only important factor related to photon dissipation (entropy production) occurring in the light-pigment interaction in living systems. He ignores the other contributions to entropy production due to the photon interaction which were listed in our article; 1) the shift towards the infrared of the emitted spectrum, 2) the diffuse emission and reflection of light into a greater outgoing solid angle, 3) the coupling of photon-induced evapotranspiration in the pigmented leaf to further photon dissipating processes such as the water cycle, which further allows dissipating biopigments to flourish over all of Earth’s surface. His assumption is therefore incorrect and his analysis does not provide legitimate reason for doubting our assertion that the fundamental molecules of life arose as pigments as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum.
In the following, we respond to each critique using the same section headings of Björn’s Comment.
Michaelian and Simeonov reply to the critique of their article: “Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum”. In response they highlight that Björn’s critique focuses almost entirely on how albedo is the only important factor is the only important factor related to photon dissipation (entropy production) occurring in the light-pigment interaction in living systems. The authors believe that other contributing factors have been overlooked by Björn’s. The authors then go into further detail regarding these additional aspects.
Comments Some of the references are not-pier reviewed or are self-published, e.g. Michaelian and Santillán Padilla 2014, and Michaelian 2009. Are there more up to date, peer reviewed articles that could replace these citations?
Section 1. L19. Change: ‘there are many data available’ to, ‘there is much data available’. L18-20. Many forests have a high seasonal variability in their albedo. For example in some latitudes, in wintertime, the albedo is more variable due to changing snow cover. Could the increased albedo in winter may be offsetting the higher irradiance in summer? L39. What do you mean by ‘bodies devoid of life’? L43. How could other factors indicative of (later) life on Earth such as oxygen affect entropy?
Section 3 L94. Reverse ‘does vegetation’. It should read ‘vegetation does’. L94-94. Further explain the role of water and the water cycle. L96. ‘Even beyond the red-edge.’ This does not follow on from the section above. L99. Reverse ‘significantly’ and ‘reduce’. ‘Significantly reduce’. L99-100. ‘An important component within biocrusts is the cyanobacterial pigment scytonemin which significantly reduces albedo…’
Section 4. L104. Include a reference at the end of the first sentence. L107-8. ‘’…which further increases the photon dissipation….’ L114. What is meant by ‘larger times’? L120-124. This sentence is too long, it needs restructuring. L128-132. I am not sure I follow the logic of this section. Please explain or expand on this to make it understandable.
We reply to Lars Björn's critique of our article concerned with the importance of photon dissipation to the origin and evolution of the biosphere. Björn doubts our assertion that organic pigments, ecosystems, and the biosphere arose out of a thermodynamic imperative to increase the entropy production of Earth. He shows that the albedo of some non-living material is less than that of living material. We point out, however, that photon dissipation involves many other factors besides albedo.
We reply to Lars Björn's critique of our article concerned with the importance of photon...