Book contents
- Evolutionary Physiology of Algae and Aquatic Plants
- Evolutionary Physiology of Algae and Aquatic Plants
- Copyright page
- Contents
- Contributors
- Preface
- Acknowledgments
- 1 Environmental Changes Impacting on, and Caused by, the Evolution of Photosynthetic Organisms
- Part I Origins and Consequences of Early Photosynthetic Organisms
- 2 Early Photosynthetic Organisms
- 3 …And Nothing Was the Same Anymore: The Rise in O2 and Consequences for Photoautotrophs
- 4 The Appearance of Eukaryotic Microalgae
- 5 The Appearance of Macroalgae: Evolution and Ecological Consequences of Multicellularity
- 6 The Evolution of Aquatic Embryophytes: Secondary Colonisers of Aquatic Environments
- Part II Physiology of Photosynthetic Autotrophs in Present-Day Environments
- Part III The Future
- Index
- References
2 - Early Photosynthetic Organisms
from Part I - Origins and Consequences of Early Photosynthetic Organisms
Published online by Cambridge University Press: 24 October 2024
- Evolutionary Physiology of Algae and Aquatic Plants
- Evolutionary Physiology of Algae and Aquatic Plants
- Copyright page
- Contents
- Contributors
- Preface
- Acknowledgments
- 1 Environmental Changes Impacting on, and Caused by, the Evolution of Photosynthetic Organisms
- Part I Origins and Consequences of Early Photosynthetic Organisms
- 2 Early Photosynthetic Organisms
- 3 …And Nothing Was the Same Anymore: The Rise in O2 and Consequences for Photoautotrophs
- 4 The Appearance of Eukaryotic Microalgae
- 5 The Appearance of Macroalgae: Evolution and Ecological Consequences of Multicellularity
- 6 The Evolution of Aquatic Embryophytes: Secondary Colonisers of Aquatic Environments
- Part II Physiology of Photosynthetic Autotrophs in Present-Day Environments
- Part III The Future
- Index
- References
Summary
Photosynthesis evolved in the Archean. Before the Great Oxidation Event, the dominant form of photosynthesis was anoxygenic bacterial photosynthesis, although there is molecular phylogenetic evidence of the occurrence of oxygenic cyanobacteria (or their ancestors) in the Archean, explaining the occurrence of ‘whiffs of oxygen’ in the Archean. Recent molecular genetic evidence shows that phototrophy is a synapomorphy of only one of the six clades of anoxygenic phototrophs (the Chlorobi) and of the oxygenic cyanobacteria, so the occurrence of phototrophy in the other five clades of anoxygenic phototrophy involves horizontal gene transfer. Photolithotrophy only occurs in three clades of anoxygenic bacteria, that is, the Chlorobi with reaction centre I for photochemistry and the reverse tricarboxylic acid cycle for CO2 fixation, the Chloroflexi with reaction centre II for photochemistry and the 3-hydroxypropionate bi-cycle or the Benson–Calvin–Bassham cycle for CO2 fixation, and the γ-proteobacteria with reaction centre 2 for photochemistry and the Benson–Calvin–Bassham cycle for CO2 fixation. The oxygenic cyanobacteria have photosystem I (homologue of reaction centre I) and photosystem II (homologue of reaction centre II) in linear electron flow, and photosystem I in cyclic electron flow, and the Benson–Calvin–Bassham cycle for CO2 fixation.
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- Evolutionary Physiology of Algae and Aquatic Plants , pp. 21 - 42Publisher: Cambridge University PressPrint publication year: 2024