The first fossils of multicellular green algae, at the Burgess shale of Canada | Source:

As the atmosphere of the Earth system changed with time, the life forms also changed. Cells evolved that could use oxygen to carry out their bodily functions. Because oxygen is a much more efficient gas, this opened the door to larger, faster, and more complex cellular life forms.

The process we call as ‘evolution’ which is gradual development of life due to adaptation is responsible for all the advances in life. The major evolutionary advance in early life was the development of multi-cellular lifeforms. No longer was life limited to just one cell. Lives began to arise that were made up of two cells, ten cells, or even thousands or billions of cells. These cells began to specialize in different functions.

Charles Darwin  ‘father of modern biology’ Pic by Herbert Rose Barraud (1881)  |  Source:
Charles Darwin
‘father of modern biology’
Pic by Herbert Rose Barraud (1881) |

In time between 2,500 million and 544 million years ago, fossils of both primitive single celled and more advanced multicellular organisms begin to appear in abundance in rocks. According to the fossil records, the oldest multi-cellular life form to be known is an ‘algae’ (a very primitive aquatic plant/sea weed which can photosynthesis). The oldest fossil evidence of multi-cellular animals, are burrowers which suggest they were made by smooth, wormlike creatures. These fossils have been found in rocks in various places including China, Canada and India. The imprints of these soft bodied animals reveal little else but their basic shape.

Natural selection
Biological evolution is a powerful and important process. It is a process which, over billions of years, gradually selects the organisms that are better adapted to their environments, and in this way takes advantage of random mutations (a change in genetic elements) to continuously change life and make all living organisms in existence be the way they are.Evolution is not a finished event, of which we, humans, are the final product.

Rather, it is a continuing process which has been changing and forming life on earth for billions of years and continues to do so for as long as organisms are being born, dying, and competing for what they need to survive and reproduce.

Biologists believe that the something that directed evolution is what is known as ‘Natural Selection’. This law says that the strongest lifeforms live, while those that are weaker die, and is often referred to as survival of the fittest. This theory of natural selection is bought up by the famous scientist called ‘Charles Darwin’. When Charles was 22, he was invited to join a voyage round the world in a ship called ‘Beagle’.

It was a ship responsible for travelling the globe, making maps of coastlines. Charles had an amazing life, he travelled the world, saw volcanoes explode and earthquakes, rode on the back of giant tortoises, and went hunting for ostriches. When he came home, he changed the way we think about living things!

He is the father of modern Biology. His Theory of Natural selection, describes loads of things in nature like fossils, peacocks’ tails, lions’ teeth, birds’ wings and human brains, just to name a few. It is also supported by lots and lots of evidence that has been collected by scientists for more than 150 years.

With all these evidences he revealed that evolution is driven by a natural force called ‘natural selection’.  The history of life is not necessarily progressive; it is certainly not predictable. The earth’s creatures have evolved through a series of contingent and fortuitous events.

Santhushya  Hewapathiranage

Amoeba, a unicellular organism (modern day)  | Source:
Amoeba, a unicellular organism (modern day) | Source:
Cosmarium, a multicellular algae (modern day) | Source:
Cosmarium, a multicellular algae (modern day) | Source:

Here are ten cool algae facts that you can use to impress
your friends and teachers


1)     The oceans cover about 71 percent of the Earth’s surface, yet algae produce more than 71 percent of the Earth’s oxygen; in fact, some scientists believe that algae produce 87 percent of the world’s oxygen. They also help remove huge amounts of Carbon Dioxide.

2)     Some algae are so cool, they can live in the snow, just like the pink-colored algae in the picture below.

3)     Some algae can live in boiling hot water, like these yellow, green, and orange algae in Yellowstone National Park.

4)     Oxygen was poisonous to the organisms that populated the early Earth. By producing oxygen, the first algae may have created the greatest toxic waste crisis in history.

5)     The descendants of some of the first algae probably live inside your cells.

6)     Some algae seem more like animals than plants.

7)     Some algae even hunt and kill fish for food!

8)     Fossilized Algae are used to make dynamite.

9)     Algae may have caused one of the most famous miracles in the Bible.

10)     Algae may be able to help save the planet.