Why is the process of photosynthesis important

Photosynthesis is the process by which plants, algae and cyanobacteria use the energy from the Sun to make sugar from water and carbon dioxide, releasing oxygen as a waste product. But a few groups of bacteria carry out a simpler form of photosynthesis that does not produce oxygen, which evolved first.

A new study by an Imperial researcher suggests that this more primitive form of photosynthesis evolved in much more ancient bacteria than scientists had imagined, more than 3.5 billion years ago.

Photosynthesis sustains life on Earth today by releasing oxygen into the atmosphere and providing energy for food chains. The rise of oxygen-producing photosynthesis allowed the evolution of complex life forms like animals and land plants around 2.4 billion years ago.

However, the first type of photosynthesis that evolved did not produce oxygen. It was known to have first evolved around 3.5-3.8 billion years ago, but until now, scientists thought that one of the groups of bacteria alive today that still uses this more primate photosynthesis was the first to evolve the ability.

But the new research reveals that a more ancient bacteria, that probably no longer exists today, was actually the first to evolve the simpler form of photosynthesis, and that this bacteria was an ancestor to most bacteria alive today.

"The picture that is starting to emerge is that during the first half of Earth's history the majority of life forms were probably capable of photosynthesis," said study author Dr Tanai Cardona, from the Department of Life Sciences at Imperial College London.

The more primitive form of photosynthesis is known as anoxygenic photosynthesis, which uses molecules such as hydrogen, hydrogen sulfide, or iron as fuel -- instead of water.

Traditionally, scientists had assumed that one of the groups of bacteria that still use anoxygenic photosynthesis today evolved the ability and then passed it on to other bacteria using horizontal gene transfer -- the process of donating an entire set of genes, in this case those required for photosynthesis, to unrelated organisms.

However, Dr Cardona created an evolutionary tree for the bacteria by analyzing the history of a protein essential for anoxygenic photosynthesis. Through this, he was able to uncover a much more ancient origin for photosynthesis.

Instead of one group of bacteria evolving the ability and transferring it to others, Dr Cardona's analysis reveals that anoxygenic photosynthesis evolved before most of the groups of bacteria alive today branched off and diversified. The results are published in the journal PLOS ONE.

"Pretty much every group of photosynthetic bacteria we know of has been suggested, at some point or another, to be the first innovators of photosynthesis," said Dr Cardona. "But this means that all these groups of bacteria would have to have branched off from each other before anoxygenic photosynthesis evolved, around 3.5 billion years ago.

"My analysis has instead shown that anoxygenic photosynthesis predates the diversification of bacteria into modern groups, so that they all should have been able to do it. In fact, the evolution of oxygneic photosynthesis probably led to the extinction of many groups of bacteria capable of anoxygenic photosynthesis, triggering the diversification of modern groups."

To find the origin of anoxygenic photosynthesis, Dr Cardona traced the evolution of BchF, a protein that is key in the biosynthesis of bacteriochlorophyll a, the main pigment employed in anoxygenic photosynthesis. The special characteristic of this protein is that it is exclusively found in anoxygenic photosynthetic bacteria and without it bacteriochlorophyll a cannot be made.

By comparing sequences of proteins and reconstructing an evolutionary tree for BchF, he discovered that it originated before most described groups of bacteria alive today.

Story Source:

Materials provided by Imperial College London. Original written by Hayley Dunning. Note: Content may be edited for style and length.

We all know that the source of life on the Earth is the Sun. But did you know that without photosynthesis, the energy derived from the Sun would be wasted, leaving behind a lifeless planet? Here’s more…

The simplest way to understand what photosynthesis is, would be to know that it refers to the process of producing and releasing oxygen into the air. It is a process performed by plants to produce their own food, and it requires direct sunlight, carbon dioxide, and water (H2O). In the process of photosynthesis, plants decompose the molecules of hydrogen and carbon dioxide into hydrogen, carbon, and oxygen, to produce glucose, which forms the source of their energy, growth, and food.

Products of Photosynthesis

The primary product of photosynthesis is glucose which is the source of carbohydrates like cellulose, starch, etc. It also produces fats, proteins, and water soluble sugars such as maltose and sucrose. The plants depend on this glucose for their growth and energy.

All the living creatures on the earth depend on fats, proteins, and carbohydrates to derive their energy, and thus, have a direct dependence on this process for their survival.

Photosynthesis and Respiration

The importance of photosynthesis can be understood with respect to our breathing process. The breathing process keeps us alive and photosynthesis provides us oxygen to breathe in.

Both the processes are inter-related, and serve one another. While photosynthesis requires carbon-dioxide and releases oxygen to produce glucose, respiration needs oxygen while inhaling and releases carbon-dioxide while exhaling.

Photosynthesis happens during the day time because the plants require sunlight to produce energy. On the other hand, respiration happens all the time as long as a living creature is alive.

When plants respire, they take in carbon dioxide from the air which aids them in preparing food (glucose). They give out oxygen as a part of the process of photosynthesis. This happens in the daytime. During night, when there is no sunlight, the stomata (pores through which sunlight and carbon-dioxide enter the leaves) are closed, and the leaves release small amounts of carbon-dioxide in the air.

Photosynthesis and Environment

The level of carbon-dioxide in the environment largely depends on the process of photosynthesis, which in turn, depends on the number of plants and trees we have. Excessive increase or decrease in the level of carbon-dioxide can bring forth disastrous results on the planet earth.

Industrial revolutions and technical progress have led to too many factories, production houses, buildings, roads etc thereby increasing the use of fuel and release of industrial waste and carbon-dioxide, which can be very harmful for the environment.

Just the way, an increase in the carbon-dioxide level may harm the environment; similarly, decrease in the level may cause the planet to freeze as CO2 helps in keeping our planet warm and live-able. Photosynthesis helps in maintaining the balance of the carbon-dioxide level in nature by taking in CO2 in the day time (and simultaneously supplying oxygen for other living beings) and releasing it at night.

Photosynthesis and Life

Photosynthesis is directly related to the life and survival of all the other living creatures on earth. It not just supplies oxygen, without which, breathing and being alive would be difficult, but it also supplies food and energy to all.

Among all the living organisms on planet earth, only plants are capable of producing their own food and deriving energy from it. No other living creature can produce their food and thus, depend on plants or other creatures which feed on plants to survive. Therefore, by producing energy, the plants supply all the necessary nutrients and energy directly and/or indirectly to the other living creatures. The production of this energy is possible through photosynthesis.

Going by all the above facts, it is evident how photosynthesis plays a vital role in regulating the life cycle on Earth. Now you may realize its importance every time you breathe in and out, and take a look at the plants at your backyard, neighborhood, or front garden. Sunlight, water, and plants work together to supply the raw source of energy to us, and help us breathe in oxygen to live on. Life without photosynthesis would thus be impossible.