Saturday, February 18, 2012

Evolutionary origin of photosynthesis traced

Scientists claim to have found the evolutionary origin of photosynthesis, the process which enables plants to turn sunlight into energy with aid of carbon dioxide. A group of international scientists lead by the Rutgers University unravelled the genome of a specific type of algae, that is supposed to be one of the earliest life forms that acquired the capability of photosynthesis. Getting to know the evolutionary step of how plants can retrieve energy from sunlight is important for our knowledge about how we came to exist, because it is one of the most important features in the evolution theory of life.

C. paradoxa 
The species of algae is called C. paradoxa, and recently had its genome unravelled. That means the sequence of all the building blocks of its DNA, the blueprint for life, are known. By comparing genomes and tracing changes over time, we can tell a lot about its origin, and how certain characteristics came to be. According to the group of scientists performing the study, C. paradoxa was there when the first living cells acquired the capability of photosynthesis.
A drawing of C. paradoxa.
A single evolutionary event ought to have caused eukaryotic cells to perform photosynthesis. Eukaryotic means having a nucleus. It is where cells store their DNA, and this concept is still used in our own cells. It is thought that about a billion years ago, C. paradoxa acquired so-called plastids, which are capable of photosynthesis. Today, we call those things chloroplasts, and they provide the typical green colour that plants have. The prehistoric plastids were engulfed by the cells, and managed to stay alive while being inside. In turn, they continued to produce energy, which benefits the cell. Basically, the cells 'ate' little machines and continued to use their capabilities. The machines are thought to be cyanobacteria, a species that evolved to possess the capability of photosynthesis. 'Energy factories' in our own cells are also thought to have been evolved from engulfing bacteria and harnessing their capabilities.

On Earth, life would not be possible without photosynthesis. We rely on oxygen, which plants produce when turning carbon dioxide and sunlight into energy and biomolecules. Also, plants make up an important part of the food chain. Without them, and without their capability of creating multicellular organisms while being able to perform photosynthesis, life as we know it cannot exist.

What the scientists have discovered is part of the history of one of the most important steps in the evolution of life. Before life on Earth could evolve into complex beings, the capability of eukaryotic cells to turn sunlight into energy was required. By discovering when and how this event took place, we learn more about the origin of life. Another important event was the creation of the first multicellular organisms, something which scientists have shown recently is surprisingly easy to achieve.

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